JP4835185B2 - Audio signal output apparatus and sound leakage reduction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an audio signal output apparatus for reducing a problem of sound leakage between first and second channels with a simple signal processing without the need for using a special terminal such as a 4-pole terminal. <P>SOLUTION: The audio signal output apparatus is provided with a 3-pole terminal including an output terminal 28L for a first channel audio signal, an output terminal 28R for a second channel audio signal, and a common earth terminal 28C, and also provided with sound leakage canceling signal summation means 30, 40 that summate the second channel audio signal decreased in response to a sound leakage ratio of the second channel audio signal leading to a first acoustic reproduction unit to the first channel audio signal to supply the resulting signal to the output terminal of the first channel audio signal and summate the first channel audio signal decreased in response to a sound leakage ratio of the first channel audio signal leading to a second acoustic reproduction unit to the second channel audio signal to supply the resulting signal to the output terminal of the second channel audio signal. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to an audio signal output device such as a music player that outputs, for example, left and right two-channel stereo audio signals to headphones, for example, and reproduces the sound, and more particularly to an invention that reduces sound leakage between channels.

  Portable music players that use headphones as sound reproducing means and reproduce sound of stereo audio signals of two left and right channels are widely used. In this case, the music player and the headphones are generally connected using a jack and a plug using a three-pole terminal. Here, the three-pole terminal means a left channel audio signal terminal, a right channel audio signal terminal, and a common ground terminal (ground) for the left channel and right channel audio signals in the case of a left and right two channel stereo signal. And 3 terminals.

  FIG. 8 shows the music player 200 and the headphones 100 connected thereto. The headphone 100 includes a headphone unit 10L for the left channel, a headphone unit 10R for the right channel, a connection plug 101 including three-pole terminals, a headphone unit 10L for the left channel, and a headphone unit 10R for the right channel. The cable 102 is connected to the terminal 101.

  The cable 102 includes a left and right channel cable connecting portion 103, where the ground sides of the left and right channels are connected in common, and the common connection point is connected to the common ground terminal COM of the connection plug 101.

  The connection plug 101 is a three-pole terminal including a left channel signal terminal portion L +, a right channel signal terminal portion R +, and a common ground terminal portion COM.

  The music player 200 is provided with a headphone jack 201 composed of a three-pole terminal corresponding to the connection plug 101 of the headphone 100. By inserting the connection plug 101 of the headphone 100 into the headphone jack 201 of the music player 200, the two-channel stereo audio signal output from the music player 200 is acoustically reproduced by the headphone units 10L and 10R for the left and right channels of the headphone 100. The

  However, when the above three-pole terminal is used, there is a problem of sound leakage between the left and right channels. This sound leakage is caused by a combination of the use of a common ground terminal for the left channel and right channel audio signals at the three-pole terminal, the resistance component included in the cable 102 of the headphones 100, and the amplifier characteristics of the music player 200. It is known to occur. This problem of sound leakage will be further described.

  FIG. 9 is an equivalent connection circuit diagram for explaining that sound leakage occurs when the connection plug 101 of the headphone 100 is inserted into the headphone jack 201 of the music player 200. In FIG. 9, in order to explain the case where the left channel audio signal leaks into the right channel, it is assumed that the left channel audio signal is a large amplitude signal and the right channel is completely silent. Further, it is assumed that the gain of the amplifier unit of the music player 200 is 1.

  As shown in FIG. 9, the left-channel large-amplitude audio signal (assumed to be an analog audio signal) from the left-channel signal source 1L is output from the headphone jack 201 through the amplifier 2L and the resistor 3L having a gain of 1. It is supplied to the terminal 4L.

  The right channel signal (analog audio signal) from the right channel signal source 1R is supplied to the right channel audio signal output terminal 4R of the headphone jack 201 through the amplifier 2R having a gain of 1 and the resistor 3R.

  In FIG. 9, the terminal 4 </ b> C that is grounded in the music player 200 is a common ground terminal of the headphone jack 201. The headphone jack 201 has a three-pole terminal configuration including a left channel audio signal output terminal 4L, a right channel audio signal output terminal 4R, and a common ground terminal 4C.

  When the connection plug 101 of the headphones 100 is inserted and connected to the headphone jack 201, as shown in FIG. 9, the left channel audio signal output terminal 4L and the common ground terminal 4C are connected to the left channel. The headphone unit 10L for the right channel is connected, and the headphone unit 10R for the right channel is connected between the right channel audio signal output terminal 4R and the common ground terminal 4C.

  As shown in FIG. 9, between the left channel audio signal output terminal 4L and the left channel headphone unit 10L, a line resistance 11L of the cable 102 is connected to the right channel audio signal output terminal 4R and the right channel. The line resistance 11R of the cable 102 exists between the headphone unit 10R, the ground-side common connection point 13C of the left and right channels, the headphone unit 10L for the left channel, and the headphone unit 10R for the right channel. Line resistances 12L and 12R exist between the common connection point 13C and the common ground terminal 4C, respectively.

  In the connection circuit configuration as described above, the left-channel large-amplitude audio signal output from the left-channel audio signal output terminal 4L passes through the left-channel headphone unit 10L and is then connected to the common ground terminal 4C. It reaches the connection point 13C and flows to the common ground terminal 4C.

  However, the common connection point 13C is also connected to the right-channel headphone unit 10R, and the large-amplitude audio signal of the left channel is coupled to the right-channel headphone unit 10R due to the presence of the common line resistor 14 and the like. Will leak and be supplied. As a result, in FIG. 9, the right channel audio signal should not exist (zero), but the right channel headphone unit 10R generates sound waves from the leaked left channel audio signal. Will end up.

  The above description is for the case where the left channel audio signal is a large amplitude audio signal and the right channel is completely silent, and the sound leakage of the left channel audio signal to the right channel headphone unit 10R has been described. However, when the right channel audio signal is a large amplitude audio signal and the left channel is completely silent, the right channel audio signal leaks to the left channel headphone unit 10L in the same manner as described above.

Here, the right channel headphone unit 10R, the magnitude of the leakage signal is supplied, the size AL of the left channel audio signal, the coefficient 1 / M L _(provided that in accordance with the characteristics of the line resistance and headphones 100 M _L> 1) a size AL / _{M L} multiplied by. In addition, the magnitude of the signal leaked and supplied to the left-channel headphone unit 10L is equal to the magnitude AR of the right-channel audio signal, and a coefficient 1 / M _R (where M _R> 1) a size AR / _{M R} multiplied by. In this specification, the coefficients 1 / _{M L} and 1 / _{M R,} referred to as sound leakage ratio.

Note that the sound leakage ratio 1 / M _L of the left channel audio signal to the right channel, the sound leakage rate 1 / M _R of the right channel audio signal to the left channel, but not necessarily identical.

  Conventionally, in order to solve the problem of sound leakage between the left and right channels, a method using a four-pole terminal has been provided as shown in FIGS. 10 and 11 (see Non-Patent Document 1 described later). That is, as shown in FIG. 10, the headphone 100 ′ in this example includes a connection plug 104 having a four-pole terminal instead of the connection plug 101 having a three-pole terminal. Other configurations of the headphone 100 'are the same as those of the headphone 100 described with reference to FIG.

  In this case, as shown in FIG. 10, the connection plug 104 includes a left channel signal terminal portion L +, a right channel signal terminal portion R +, a left channel ground terminal portion L-, and a right channel ground terminal portion R-. It is set as the structure of 4 pole terminals.

  FIG. 11 is an equivalent connection circuit diagram in a state where the connection plug 104 of the 4-pole terminal of the headphone 100 ′ is inserted into the headphone jack of the music player 200. Also in FIG. 11, in order to explain the case where the left channel audio signal leaks to the right channel, as in FIG. 9, the left channel audio signal is a large amplitude signal and the right channel is completely silent. Suppose there is. Further, it is assumed that the gain of the amplifier unit of the music player 200 is 1.

  As shown in FIG. 11, in the case of using the connection plug 104 composed of this four-pole terminal, a music player is used as a connection point between the left channel ground terminal portion L- of the connection plug 104 and the ground terminal of the headphone jack 201. The left channel ground terminal 5L of 200 is configured, and the R channel ground terminal 5R of the music player 200 is used as a connection point between the right channel ground terminal portion R- of the connection plug 104 and the ground terminal of the headphone jack 201. Is configured.

  Therefore, in the case of using the connection plug 104 composed of this 4-pole terminal, the common connection point 13C and the common line resistance 14C do not exist as in the case of the 3-pole terminal described with reference to FIG. The large amplitude audio signal of the channel is supplied to the ground terminal 5L after passing through the left channel headphone unit 10L, and the problem of sound leakage from the left channel to the right channel is avoided.

  In the case of using the connection plug 104 composed of this four-pole terminal, the problem of sound leakage from the right channel to the left channel is similarly avoided.

The above non-patent documents are as follows.
SHARP “Equipped with“ Mobile 1-bit digital amplifier-H / A- ”that realizes high-quality sound that is more faithful to the original sound”, [online], [searched on January 30, 2006], Internet <URL: http: / /www.sharp.co.jp/products/mdds700/text/1bit.html>

  As described above, according to the method using the connection plug including the four-pole terminals, it is possible to avoid the problem of sound leakage between the left and right channels. However, a connection plug comprising a four-pole terminal is not a general one but a special one, which is not preferable because it forces the user to purchase the special headphones.

  The above description is for the case of left and right two-channel stereo audio signals. For example, when the left channel is replaced with the first channel and the right channel is replaced with the second channel, these first channel audio signals and The same problem arises when considering the case where an audio signal other than the left and right two-channel stereo signals is reproduced as the second channel audio signal.

  An object of the present invention is to provide an apparatus and method that can reduce the above-described problem of sound leakage between the first and second channels by simple signal processing without using the special four-pole terminal as described above. And

In order to solve the above problems, the present invention provides:
A three-pole terminal comprising an output terminal for a first channel audio signal, an output terminal for a second channel audio signal, and a common ground terminal for the first channel audio signal and the second channel audio signal, A first sound reproduction unit that reproduces sound of the first channel audio signal and a second sound reproduction unit that reproduces sound of the second channel audio signal are connected, and an external terminal having a terminal corresponding to the three-pole terminal is connected. A three-pole terminal,
The second channel audio signal reduced according to the second sound leakage ratio when the second channel audio signal leaks to the first sound reproduction unit through the common ground terminal to the first channel audio signal. In addition, the first channel audio signal is supplied to the output terminal of the first channel audio signal, and the second channel audio signal is connected to the second sound reproduction unit via the common ground terminal. Sound leakage elimination signal adding means for adding the first channel audio signal reduced in accordance with the first sound leakage ratio when leaking to the output terminal and supplying it to the output terminal of the second channel audio signal;
To provide an audio signal output device comprising a.

According to the present invention having the above-described configuration, the second channel audio signal component corresponding to the sound leakage component that arrives at the first sound reproduction unit from the second channel audio signal side via the common ground terminal is first stored in advance. It is added to the channel audio signal. Therefore, in the first sound reproduction unit, the second channel audio signal component added to the first channel audio signal and the sound leakage component arriving from the second channel audio signal side through the common ground terminal cancel each other out. Accordingly, the sound leakage component is canceled.

Similarly, the first channel audio signal component corresponding to the sound leakage component arriving at the second sound reproduction unit from the first channel audio signal side via the common ground terminal is added to the second channel audio signal in advance. . Therefore, in the second sound reproduction unit, the first channel audio signal component added to the second channel audio signal and the sound leakage component coming from the first channel audio signal side via the common ground terminal cancel each other out. Accordingly, the sound leakage component is canceled.

  According to the present invention, the problem of sound leakage between the first and second channels can be reduced by simple signal processing without using a special four-pole terminal.

  Hereinafter, an audio signal output device according to an embodiment of the present invention will be described with reference to the drawings, taking as an example a case where a left and right two-channel stereo signal is applied to a music player that reproduces sound using headphones.

[First embodiment]
FIG. 2 is a block diagram illustrating a configuration example of the music player 300 according to the first embodiment. The music player in this example includes, for example, a hard disk device, a semiconductor memory, an optical disk drive, and the like, includes a music content storage unit 21 that stores data of music content, and includes a control unit 301 configured using, for example, a microcomputer, and An operation input unit 302 is provided.

  The music player of this embodiment includes a headphone jack 28 having a three-pole terminal configuration, and the headphone jack 28 is connected to the headphone 100 having the three-pole terminal as shown in FIG. The plug 101 is configured to be inserted. That is, the headphone jack 28 of the music player of this embodiment includes a three-pole terminal including an output terminal 28L for a left channel audio signal, an output terminal 28R for a right channel audio signal, and a common ground terminal 28C.

  The control unit 301 controls to read out the music content selected by the user from the music content storage unit 21 in response to the selection input of the user's music content through the operation input unit 302 and the reproduction request thereof.

  The music data of the music content read from the music content storage unit 21 is supplied to the music data decoding unit 22 and decoded. The music data decoding unit 22 outputs left and right two-channel digital audio signals (PCM (Pulse Code Modulation) audio signals) DL and DR.

  The digital audio signals DL and DR are supplied to the D / A converters 23L and 23R, converted into analog audio signals, and then supplied to the switch circuit 24.

  In this example, the switch circuit 24 and the switch circuit 26 to be described later are provided so that the user can select whether to perform the sound leakage countermeasure process for the left and right channels or not to perform the sound leakage countermeasure process. It has been. The control unit 301 supplies a switching control signal SW to the switch circuit 24 and the switch circuit 26 in response to a selection input for the presence or absence of sound leakage countermeasures through the user operation input unit 302.

  When the user inputs a selection operation unless sound leakage countermeasure processing is performed through the operation input unit 302, the control unit 301 switches the switch circuit 24 and the switch circuit 26 to the switching state of FIG. 2 as the switching control signal SW. The control signal to be supplied is supplied to the switch circuit 24 and the switch circuit 26.

  At this time, the left and right two-channel analog audio signals from the D / A converter 23L and the D / A converter 23R are supplied to the switch circuit 26 through the analog amplifier 25L and the analog amplifier 25R, respectively. At this time, since the switch circuit 26 is switched to the state shown in FIG. 2, the left and right channel analog audio signals pass through the resistor 27L and the resistor 27R, respectively, and the left channel audio signal output terminal 28L and the right channel audio signal. It is supplied to each of the output terminals 28R.

  In addition, when the user inputs a selection operation when performing the sound leakage countermeasure process through the operation input unit 302, the control unit 301 sets the switch circuit 24 and the switch circuit 26 as the switching control signal SW in the reverse of the switching state in FIG. A control signal for switching to the state is supplied to the switch circuit 24 and the switch circuit 26.

  At this time, the left and right channel analog audio signals from the D / A converter 23L and the D / A converter 23R are supplied to the sound leakage elimination signal adding unit 30. The sound leakage cancellation signal adding unit 30 performs processing for adding a signal for canceling sound leakage between the left and right channels to each of the left channel audio signal and the right channel audio signal, as will be described later.

  The left and right two-channel analog audio signals OL and OR to which the sound leakage canceling signal is added from the sound leakage canceling signal adding unit 30 are left through the switch circuit 26 and the resistors 27L and 27R, respectively. It is supplied to each of the channel audio signal output terminal 28L and the right channel audio signal output terminal 28R.

  Next, FIG. 1 explains that sound leakage is canceled and reduced in the first embodiment when the connection plug 101 of the headphone 100 is inserted into the headphone jack 28 of the music player 300. It is an equivalent connection circuit diagram for this.

  In FIG. 1, even when the left channel audio signal is a large amplitude signal and the right channel is completely silent, the leakage of the left channel audio signal to the right channel is canceled and reduced. It shows how it is done. The signal source 20L represents the signal source of the left channel digital audio signal DL from the music data decoding unit 22, and the signal source 20R represents the right channel digital audio signal DL from the music data decoding unit 22. The signal source is shown.

  A detailed configuration example of the sound leakage elimination signal adding unit 30 in the music player 300 of the first embodiment is as shown in FIG. The sound leakage cancellation signal adding unit 30 in the first embodiment has a configuration of an analog signal processing circuit.

  That is, in the sound leakage elimination signal adding unit 30 in this embodiment, the left channel analog audio signal from the D / A converter 23L is supplied to the adding unit 32L through the left channel analog output amplifier 31L. The right channel analog audio signal from the D / A converter 23R is supplied to the adder 32R through the right channel analog output amplifier 31R.

  The analog audio signal of the left channel from the D / A converter 23L is supplied to the adder 32R through the sound leakage canceling signal generating amplifier 33L and added to the analog audio signal of the right channel.

  The right channel analog audio signal from the D / A converter 23R is supplied to the adder 32L through the sound leakage canceling signal generating amplifier 33R and added to the left channel analog audio signal.

At this time, as described above, when the sound leakage ratio of the left channel audio signal to the right channel is 1 / M _L and the sound leakage ratio of the right channel audio signal to the left channel is 1 / M _R , the amplifier The gain of 33L is 1 / M _L (where M _L > 1), and the gain of the amplifier 33R is 1 / M _R (where M _R > 1).

  As a result, the output signal CL of the amplifier 33L becomes a sound leakage cancellation signal of the left channel audio signal leaking to the right channel, and the output signal CR of the amplifier 33R is a sound leakage cancellation of the right channel audio signal leaking to the left channel. To be a signal.

In this example, for the output of the adder 32L and the addition unit 32R is to be a gain 1, gain of the amplifier 31L is a 1-1 / _{M R,} amplifiers 31R of gain 1-1 / are _{M L.}

  As described above, the left-channel audio signal and the right-channel audio signal to which the sound leakage cancellation signal has been added respectively are output from the adder 32L and adder 32R through the resistors 27L and 27R, respectively. 28L and the right channel audio signal output terminal 28R.

  As a result of the above configuration, in the first embodiment, as described below, the sound leakage signal between the left and right channels is canceled by the sound leakage cancellation signals CL and CR, and sound leakage occurs. Is reduced.

  That is, in FIG. 1, as in the case of FIG. 9 described above, the left-channel large-amplitude audio signal output from the left-channel audio signal output terminal 28L passes through the left-channel headphone unit 10L, and is then connected to the common ground. It reaches the common connection point 13C connected to the terminal 4C and flows to the common ground terminal 28C.

  Since the common connection point 13C is also connected to the right-channel headphone unit 10R, the large-amplitude audio signal of the left channel is combined with the presence of the common line resistor 14 and the right-channel headphone unit 10R. It will be in the state which leaks and is supplied.

  However, in the first embodiment, as shown in FIG. 1, the sound leakage canceling signal CL corresponding to the leakage of the left channel audio signal to the right channel through the amplifier 33L is output to the right channel audio in the adder 32R. It is added to the signal. In FIG. 1, since the audio signal of the right channel does not exist (is zero), the adder 32R outputs the sound leakage cancellation signal CL supplied through the amplifier 33L. The signal is supplied to the right channel headphone unit 10R through the right channel audio signal output terminal 28R.

  As a result, in the right channel headphone unit 10R, the signal component leaking from the left channel side via the common connection point 13C and the sound leakage cancellation signal CL are canceled and canceled, and the right channel headphone unit 10R Sound waves due to sound leakage signals are not generated or reduced.

  FIG. 1 illustrates the case where the left channel audio signal leaks to the right channel as described above, but when the right channel audio signal leaks to the left channel, the amplifier 33R added to the adder 32L. The sound leakage canceling signal CR cancels out the leakage in the left channel headphone unit 10L, and the sound wave due to the sound leakage signal is not generated or reduced from the right channel headphone unit 10R. .

  As a result, the information originally possessed by the left and right channel audio signals can be transmitted to the user more accurately to the headphone user, and so-called separation between channels is improved.

  In the above-described embodiment, since the user can select whether or not to use the sound leakage elimination signal adding unit 30, a connection plug other than the connection plug of the headphone 100 is connected to the headphone jack 28. For example, when the audio signal output from the head jack 28 is reproduced by two external speakers, or the audio signal output from the head jack 28 is sent to another audio device, the sound leakage elimination signal is added. The original left and right channel audio signals can be output.

In the above embodiment, the value of the sound leakage ratio 1 / M _L and 1 / M _R, for instance when only the assumed when headphones 100 is supplied with the music player 300, an output audio signal of the music player 300 sound leakage ratio 1 / _{M L} and 1 / _{M R} when the music listening with headphones 100 by measuring, the measured sound leakage ratio 1 / _{M L} and 1 / _{M R} fixedly, amplifiers 33L, 33R, It can be set to 31L and 31R.

However, considering that the characteristics of the music player 300 and the characteristics of the headphones 100 may not all be the same, and that the user does not always use only the headphones 100 attached to the music player 300, the sound leakage ratio 1 / when the value of M _L and 1 / M _R set fixedly, there is a possibility that desired ones can not be obtained as an effect of the sound leakage erased. In consideration thereof, the amplifiers 33L and 33R are configured as variable gain amplifiers, and the control unit 301 controls the gains of the variable gain amplifiers 33L and 33R by the user's gain adjustment input through the operation input unit 302. It is better to configure so that it can.

  In other words, in this case, the music player 300 is provided with a sound leakage ratio setting mode, and, for example, in contrast to the first test signal in which the left channel audio signal is a large amplitude signal and the right channel audio signal is zero. The music player 300 may be provided with a test signal that outputs a second test signal in which the right channel audio signal is a large amplitude signal and the left channel audio signal is zero for a predetermined time. .

  The user selects the sound leakage ratio setting mode, plays the first test signal and the second test signal on the music player 300, and confirms the sound leakage in the headphones used at that time. The gains of the variable gain amplifiers 33L and 33R are adjusted using the operation input unit 302. Thus, an appropriate value corresponding to the sound leakage ratio can be set as the gain of the variable gain amplifiers 33L and 33R.

  In the embodiment of FIG. 1, the gains of the amplifier 31L and the amplifier 31R are adjusted so that the gain of the output signal does not change even when the sound leakage cancellation signal is added to the left and right channel audio signals. Since this is an analog audio signal, the gains of the amplifiers 31L and 31R may be fixed at 1 without adjusting the gains of the amplifiers 31L and 31R.

[Second Embodiment]
The first embodiment is an example in which a sound leakage cancellation signal is added to each channel audio signal at the stage of an analog audio signal. However, when analog elements / circuits are used, characteristics may not be stable due to variations in elements. In addition, when an analog element is used, there are problems that its component cost, circuit scale, and power consumption increase.

  In the second embodiment, in view of this point, when the audio signal is a digital signal, the sound leakage elimination signal is added to the audio data of each channel by digital processing.

  FIG. 3 is a block diagram showing an example of the configuration of the music player 300 in the case of the second embodiment. The same components as those of the music player in the case of the first embodiment shown in FIG. Is attached.

  In the second embodiment, as shown in FIG. 3, the music data decoding unit 22 includes a switch circuit 29 that can be switched between the case where the sound leakage countermeasure process is performed for the left and right channels and the case where the sound leakage countermeasure process is not performed. And D / A converters 23L and 23R.

  In the second embodiment, when the user inputs a selection operation unless the sound leakage countermeasure process is performed through the operation input unit 302, the control unit 301 uses the switch circuit 29 as the switching control signal SW in FIG. A control signal for switching to the switching state is supplied to the switch circuit 29.

  At this time, the left and right channel digital audio data DL and DR from the music data decoding unit 22 are supplied to the D / A converter 23L and the D / A converter 23R through the switch circuit 29, respectively, and analog audio Converted to a signal. The left and right two-channel analog audio signals from the D / A converter 23L and the D / A converter 23R pass through the analog amplifier 25L and the analog amplifier 25R, respectively, and also through the resistors 27L and 27R, respectively. The signal is supplied to each of the signal output terminal 28L and the right channel audio signal output terminal 28R.

  Further, when the user inputs a selection operation to perform the sound leakage countermeasure process through the operation input unit 302, the control unit 301 switches the switch circuit 28 to a state opposite to the switching state of FIG. 3 as the switching control signal SW. A control signal is supplied to the switch circuit 28.

  At this time, the left and right channel digital audio data DL and DR from the music data decoding unit 22 are supplied to the sound leakage elimination signal adding unit 40 of the digital signal processing. In the sound leakage elimination signal adding unit 40, as will be described later, in the digital signal stage, a signal for eliminating sound leakage between the left and right channels is added to each of the left channel audio signal and the right channel audio signal. I do.

In the second embodiment, the sound leakage cancellation signal addition unit 40, sound leakage ratio 1 / M _L and 1 / M _R is, are adjustable by a user operation input through the operation input section 302, the Therefore, the control unit 301 generates an adjustment control signal CTL of sound leakage ratio 1 / M _L and 1 / M _R corresponding to a user operation input through the operation input section 302, sound leakage erase the generated adjustment control signal CTL The signal adding unit 40 is configured to be supplied.

  The left and right two-channel digital audio signals DOL and DOR, to which the sound leakage cancellation signal is added, are supplied from the sound leakage cancellation signal adding unit 40 to the D / A converter 23L and the D / A converter 23R, respectively. Are converted into analog audio signals. The left and right two-channel analog audio signals from the D / A converter 23L and the D / A converter 23R pass through the analog amplifier 25L and the analog amplifier 25R, respectively, and also through the resistors 27L and 27R, respectively. The signal is supplied to each of the signal output terminal 28L and the right channel audio signal output terminal 28R.

  Next, FIG. 4 illustrates that in the second embodiment, sound leakage is canceled and reduced when the connection plug 101 of the headphone 100 is inserted into the headphone jack 28 of the music player 300. It is an equivalent connection circuit diagram for this.

  In this FIG. 4, as in the case of FIG. 1, even if the left channel audio signal is a large amplitude signal and the right channel is completely silent, the right channel of the left channel audio signal is shown. This shows how the sound leakage to the is canceled and reduced.

  A detailed configuration example of the sound leakage elimination signal adding unit 40 in the music player 300 of the second embodiment is as shown in FIG. The sound leakage cancellation signal adding unit 40 in the second embodiment has a configuration of a digital signal processing circuit.

  That is, in the sound leakage elimination signal adding unit 40 in this embodiment, the digital audio signal DL of the left channel from the music data decoding unit 22 is supplied to the adding unit 42L through the coefficient multiplication unit 41L for adjusting the sound leakage ratio. At the same time, the digital audio signal DR of the right channel from the music data decoder 22 is supplied to the adder 42R through the coefficient multiplier 41R for adjusting the sound leakage ratio.

  Then, the digital audio signal DL of the left channel from the music data decoding unit 22 is supplied to the adding unit 42R through the coefficient multiplier 43L for generating the sound leakage cancellation signal, and is added to the digital audio signal of the right channel.

  Also, the right channel digital audio signal DR from the music data decoding unit 22 is supplied to the adder 42L through the coefficient multiplier 43R for generating a sound leakage elimination signal, and added to the left channel digital audio signal.

At this time, as described above, sound leakage ratios 1 / M L of the left channel audio signal to the right _channel, also when the sound leakage ratio of the right channel audio signal to the left channel and 1 / M _R, coefficient The coefficient multiplied by the multiplier 43L is 1 / M _L (where M _L > 1), and the coefficient multiplied by the coefficient multiplier 43R is 1 / M _R (where M _R > 1). The As described above, the coefficient 1 / _{M L} and 1 / _{M R} is the adjustment control signal CTL from the control unit 301, is variable.

  As a result, the output signal DCL of the coefficient multiplier 43L becomes a sound leakage elimination signal of the left channel audio signal leaking to the right channel, and the output signal DCR of the coefficient multiplier 43R is the right channel audio signal leaking to the left channel. The sound leakage canceling signal is set as follows.

Then, in the second embodiment, by addition in the adding unit 42L and the addition unit 42R, in order to prevent an overflow in the digital domain, the coefficients are multiplied by the coefficient multiplying unit 41L is a 1-1 / M _R , the coefficient to be multiplied by the coefficient multiplying unit 41R is a 1-1 / _{M L.}

Here, as described above, the coefficient 1 / _{M L} and 1 / _{M R,} is intended to be variable by adjustment control signal CTL from the control unit 301.

  As described above, the left-channel digital audio signal DOL and the right-channel digital audio signal DOR to which the sound leakage elimination signals are added are respectively supplied from the adder 42L and the adder 42R to the D / A converters 23L and 23R. To be converted into an analog audio signal. Then, the converted analog audio signals of the left channel and the right channel are supplied to the left channel audio signal output terminal 28L and the right channel audio signal output terminal 28R through the resistor 27L and the resistor 27R, respectively.

  As a result, in the same manner as in the first embodiment, in the right channel headphone unit 10R, the signal component leaking from the left channel side via the common connection point 13C and the sound leakage cancellation signal CL are mutually connected. Canceled by cancellation, the sound wave due to the sound leakage signal is not generated or reduced from the right-channel headphone unit 10R.

  FIG. 4 illustrates the case where the left channel audio signal leaks to the right channel. When the right channel audio signal leaks to the left channel, sound leakage from the coefficient multiplier 43R added to the adder 42L. The erasure signal DCR cancels the leakage by canceling the left channel headphone unit 10L, and the sound wave due to the sound leakage signal is not generated or reduced from the right channel headphone unit 10R.

  FIG. 5 shows a more detailed configuration example of the sound leakage cancellation signal adding unit 40 of FIG. As shown in FIG. 5, the sound leakage elimination signal adding unit 40 is a digital product-sum operation unit.

  As shown in FIG. 5, in the sound leakage elimination signal adding unit 40 of this example, the left channel digital audio signal DL and the right channel digital audio signal DR from the music data decoding unit 22 are input to the input buffer registers 44L and 44R. Samples are taken one by one. Each time new digital audio sample data is taken into the input buffer registers 44L and 44R, the previous data is discarded from the input buffer registers 44L and 44R.

  The left channel sample data taken into the input buffer register 44L is supplied to the multipliers 45L and 47L, respectively, and the coefficient values stored in the coefficient register 46L and the coefficient register 48L respectively multiply the sample data. Is done.

Here, the multiplication unit 45L and the coefficient register 46L constitute the coefficient multiplication unit 41L of FIG. 4, and the multiplication unit 47L and the coefficient register 48L constitute the coefficient multiplication unit 43L of FIG. the 46L, 1-1 / _{M L} is stored as a coefficient value, also, the coefficient register 48L, sound leakage ratio 1 / _{M L} is stored as a coefficient value.

  In this example, the coefficient values of the coefficient registers 46L and 48L are varied by the adjustment control signal CTL from the control unit 301. Or the control part 301 produces | generates the coefficient value according to adjustment operation input of a user's sound leakage ratio, and supplies the produced | generated value to the coefficient registers 46L and 48L as the coefficient value.

  The multiplication output from the multiplication unit 45L is supplied to the addition unit 42L for the left channel. The multiplication output from the multiplication unit 47L is supplied to the right channel addition unit 42R.

  Similarly, the right channel sample data fetched into the input buffer register 44R is supplied to the multipliers 45R and 47R, respectively, and the coefficient values stored in the coefficient register 46R and the coefficient register 48R respectively correspond to the respective sample data. Is multiplied by

Here, the multiplier 45R and the coefficient register 46R constitute the coefficient multiplier 41R of FIG. 4, and the multiplier 47R and the coefficient register 48R constitute the coefficient multiplier 43R of FIG. the 46R, 1-1 / _{M R} is stored as a coefficient value, also, the coefficient register 48R, the sound leakage ratio 1 / _{M R} is stored as a coefficient value.

  In this example, the coefficient values of the coefficient registers 46R and 48R are varied by the adjustment control signal CTL from the control unit 301. Or the control part 301 produces | generates the coefficient value according to adjustment operation input of a user's sound leakage ratio, and supplies the produced | generated value to the coefficient registers 46R and 48R as the coefficient value.

  The multiplication output from the multiplication unit 45R is supplied to the right channel addition unit 42R. The multiplication output from the multiplication unit 47R is supplied to the addition unit 42L of the left channel.

  From the above, the left and right two-channel digital audio signals DOL and DOR to which the sound leakage cancellation signal has been added are obtained from the adders 42L and 42R. As shown in FIG. 3, each D / A converter 23L is obtained. And supplied to the D / A converter 23R to be converted into an analog audio signal.

  The method for determining the coefficients to be set in the coefficient registers 46L, 46R, 48L, and 48R is similar to the method described in the first embodiment described above, and is provided with a coefficient setting mode and the first and second modes. This test signal can be used to adjust the coefficient to an optimum value so that sound leakage is minimized.

  The example of FIG. 5 is a case where the sound leakage elimination signal adding unit 40, which is a digital signal processing unit, has a hardware configuration including a product-sum operation unit. It is also possible to execute the digital audio data DL and DR from the unit 22 as software processing while taking one sample at a time.

  FIG. 6 is a flowchart showing a processing procedure in the case of such software processing. In this case, the processing of each step in FIG. 6 is executed by the microcomputer of the control unit 301 in FIG.

That is, the control unit 301 first takes in the left and right channel digital audio signals DL and DR from the audio data decoding unit 22 as input sample data (step S101). Next, the control unit 301 reads the coefficients 1 / M _L , 1 / M _R , 1-1 / M _L , and 1-1 / M _R stored in a coefficient register (not shown) (step S102).

Then, the control unit 301
DOL = DL × (1-1 / M _R ) + DR × 1 / M _{R
DOR = DR × (1-1 / M} L) + DL × 1 / M L
... (Formula A)
Is executed (step S103).

  Next, the control unit 301 supplies the digital signals DOL and DOR obtained in step S103 to the D / A converter 23L and the D / A converter 23R, converts them into analog audio signals, and outputs them. (Step S104).

  Then, the control unit 301 determines whether or not to end the audio output depending on whether or not the music data of the music content from the music content storage unit 21 has ended and whether or not the user has given a playback stop instruction. (Step S105) When it is determined that the audio output is not finished yet, the process returns to Step S101, and the processes after Step S101 are repeated. If it is determined in step S104 that the audio output is to be ended, the processing routine of FIG. 6 is ended.

Note that the coefficients 1 / M _L , 1 / M _R , 1-1 / M _L , and 1-1 / M _R set in the coefficient register are the same as those in the first and second embodiments described above. A test signal is used and set in advance by the user.

  When performing the above-described software processing, there is an advantage that hardware for performing the product-sum operation of the above (formula A) becomes unnecessary.

[Third Embodiment]
In the second embodiment described above, the amount of sound leakage can be adjusted and set by the user according to the headphones worn in the music player 300, and the magnitude of the sound leakage cancellation signal is optimized. It can be set to. However, in the above embodiment, the phase of the sound leakage cancellation signal is not considered. That is, in each of the headphone units 10L and 10R, when the phase of the sound leakage cancellation signal and the audio signal of the channel to be deleted do not match, a good canceling effect may not be obtained.

  The third embodiment is a case where the phase of the sound leakage cancellation signal can be adjusted by the user.

  The method for adjusting the phase of the sound leakage cancellation signal can also be applied to the case where the sound leakage cancellation signal adding unit 30 is provided at the stage of the analog audio signal described in the first embodiment. That is, in the sound leakage cancellation signal adding unit 30 of FIG. 1, variable delay means of an analog circuit, for example, a phase shift circuit, is provided on the input side or output side of the amplifier 33L and the input side and output side of the amplifier 33R. good.

  However, it is difficult to perform accurate phase adjustment in an analog circuit. Therefore, in the third embodiment, phase adjustment means is provided in the sound leakage elimination signal adding unit 40 at the stage of the digital audio signal of the second embodiment. In this case, the phase adjustment is performed in units of digital audio data samples.

  FIG. 7 is a block diagram showing a configuration example of the sound leakage cancellation signal adding unit 40 in the case of the third embodiment. In the example of FIG. 7, n-stage (n is an integer of 2 or more) shift registers 440L and 440R are provided instead of the input buffer registers 44L and 44R of the example of FIG. The n-stage shift registers 440L and 440R output digital data delayed by 0, 1, 2,..., N−1 samples from the input digital data, respectively, as the output of each stage.

  In the example of FIG. 7, the first stage outputs L [n−1] and R [n−1] of the shift registers 440L and 440R are the input digital data itself, and the i-th stage outputs L [i] and R [i]. The smaller the value of i, the larger the delay amount, and the outputs L [0] and R [0] are data samples delayed by n-1 samples from the input digital data.

The first stage outputs L [n−1] and R [n−1] of the shift registers 440L and 440R are supplied to the multipliers 45L and 45R, respectively, and are stored in the coefficient registers 46L and 46R. It is multiplied by the M _L and 1-1 / _{M R.} The multiplication results of the multipliers 45L and 45R are supplied to the adders 42L and 42R, respectively.

  On the other hand, multiplication units 47L [0], 47L [1], 47L [2],..., 47L [N−1] and multiplication unit 47R [0] are applied to the register outputs of the shift registers 440L and 440R. ], 47R [1], 47R [2],..., 47R [N-1].

Then, in each of the multiplication units 47L [0], 47L [1], 47L [2],..., 47L [N−1] for the left channel, the coefficient 1 / M stored in the coefficient register 48L. _L is multiplied by the register output of each stage, and the multiplication result is supplied to the selector 49L. The selector 49L is supplied from the control unit 301 with a selection control signal SELL corresponding to an operation input through the user operation input unit 302. From the selector 49L, one multiplication result selected by the selection control signal SELL among the multiplication results of the multiplication units 47L [0], 47L [1], 47L [2],..., 47L [N−1]. The selected one multiplication result is supplied to the adder 42R with the right channel signal.

Further, in each of the multiplication units 47R [0], 47R [1], 47R [2],..., 47R [N−1] for the right channel, the coefficient 1 / M stored in the coefficient register 48R. _R is multiplied by the register output of each stage, and the multiplication result is supplied to the selector 49R. The selector 49R is supplied with a selection control signal SELR according to an operation input from the control unit 301 through the user operation input unit 302. From the selector 49R, one multiplication result selected by the selection control signal SELR among the multiplication results of the multiplication units 47R [0], 47R [1], 47R [2],..., 47R [N−1]. And the selected one multiplication result is supplied to the adder 42L with the left channel signal.

In the music player 300 of the third embodiment in which the sound leakage elimination signal adding unit 40 is configured as described above, a coefficient and phase setting mode is provided, and the first test signal and the second test signal as described above are provided. Coefficients 1 / M _L , 1 / M _R , 1-1 / M _L , 1-1 / M _{R are} set and phase adjustment is performed using the test signal.

That is, the user places the music player 300 in the coefficient and phase setting mode, and for example, first reproduces the first test signal. In a state where the first test signal is reproduced, so that sound leakage amount of the left channel of the signal to the right channel is minimized, it sets a coefficient 1 / M _L. At this time, the coefficient supplied to the multiplication unit 45L is set to a value that does not overflow the multiplication result.

Then, store the coefficients 1 / M _L, which is set as described above in the coefficient register 48L. Moreover, to calculate the coefficient 1-1 / _{M L,} and stores the calculation result to the coefficient register 46R.

  Next, the first test signal is continuously reproduced, and the selection control signal SELL to the selector 49L is adjusted so that the sound leakage amount of the left channel signal to the right channel is minimized. Then, the selection control signal SELL as the adjustment result is held as the selection control signal SELL of the selector 49L.

Next, the test signal to be reproduced is changed to the second test signal, and the same operation as above is performed for the right channel. That is, in a state in which the second test signal is reproduced, so that sound leakage amount of the right channel of the signal to the left channel is minimized, sets a coefficient 1 / M _R. At this time, the coefficient supplied to the multiplication unit 45R is set to a value such that the multiplication result does not overflow.

Then, store the coefficients 1 / M _R which is set as described above in the coefficient register 48R. Moreover, to calculate the coefficient 1-1 / _{M R,} and stores the calculation result to the coefficient register 46L.

  Next, the second test signal is continuously reproduced, and the selection control signal SELR to the selector 49R is adjusted so that the sound leakage amount of the right channel signal to the left channel is minimized. Then, the selection control signal SELR as the adjustment result is held as the selection control signal SELR of the selector 49R.

  In the third embodiment, since the phase of the sound leakage cancellation signal can be adjusted, further improvement in the sound leakage cancellation effect can be expected.

[Other Embodiments or Modifications]
In the above-described embodiment, the sound leakage reduction method has been described by taking the case of a stereo audio signal of two left and right channels as an example. However, the first channel audio signal and the second channel audio signal are Needless to say, it is not limited to the right channel signal.

  The audio signal output device is a music player. However, the present invention is not limited to a music player, and any audio signal output terminal having a three-pole terminal configuration can be applied to the present invention. Needless to say.

It is a circuit diagram for demonstrating 1st Embodiment of the sound leak reduction method by this invention. It is a block diagram which shows the structural example of the music player of the example of the apparatus to which 1st Embodiment of the sound leakage reduction method by this invention is applied. It is a block diagram which shows the structural example of the music player of the example of the apparatus to which 2nd Embodiment of the sound leakage reduction method by this invention is applied. It is a circuit diagram for demonstrating 2nd Embodiment of the sound leak reduction method by this invention. It is a block diagram which shows the structural example for implement | achieving 2nd Embodiment of the sound leak reduction method by this invention. It is a flowchart which shows the structural example for implement | achieving 2nd Embodiment of the sound leak reduction method by this invention. It is a block diagram which shows the structural example for implement | achieving 3rd Embodiment of the sound leak reduction method by this invention. It is a figure for demonstrating an apparatus provided with a 3 pole terminal. It is a figure for demonstrating the sound leakage between channels in the case of using a 3 pole terminal. It is a figure for demonstrating the apparatus which uses a 4 pole terminal in order to reduce sound leakage. It is a figure for demonstrating the sound leakage reduction between channels in the case of using a 4-pole terminal.

Explanation of symbols

28 ... Headphone jack, 28L ... Left channel audio signal output terminal, 28R ... Right channel audio signal output terminal, 28C ... Common ground terminal, 30 ... Sound leakage elimination signal adding unit (in case of analog processing), 40 ... Sound leakage elimination signal Adder (for digital processing)

Claims (11)

A three-pole terminal comprising an output terminal for a first channel audio signal, an output terminal for a second channel audio signal, and a common ground terminal for the first channel audio signal and the second channel audio signal, A first sound reproduction unit that reproduces sound of the first channel audio signal and a second sound reproduction unit that reproduces sound of the second channel audio signal are connected, and an external terminal having a terminal corresponding to the three-pole terminal is connected. A three-pole terminal,
The second channel audio signal reduced according to the second sound leakage ratio when the second channel audio signal leaks to the first sound reproduction unit through the common ground terminal to the first channel audio signal. In addition, the first channel audio signal is supplied to the output terminal of the first channel audio signal, and the second channel audio signal is connected to the second sound reproduction unit via the common ground terminal. Sound leakage elimination signal adding means for adding the first channel audio signal reduced in accordance with the first sound leakage ratio when leaking to the output terminal and supplying it to the output terminal of the second channel audio signal;
Audio signal output device comprising a. The audio signal output device according to claim 1.
The first channel audio signal and the second channel audio signal are analog audio signals,
The sound leakage elimination signal adding means is
A first analog amplifier having a gain according to the second sound leakage ratio;
A second analog amplifier having a gain according to the first sound leakage ratio;
A first adding means for adding the first channel audio signal and the second channel audio signal through the first analog amplifier and outputting the sum to the output terminal of the first channel audio signal;
A second adding means for adding the second channel audio signal and the first channel audio signal through the second analog amplifier and outputting the sum to the output terminal of the second channel audio signal;
Audio signal output device comprising a. The audio signal output device according to claim 2,
The first and second analog amplifiers are variable gain amplifiers that receive a gain control signal and vary the gain,
Control means for receiving a gain control operation input from a user and supplying the gain control signal to each of the first and second analog amplifiers.
Audio signal output device. The audio signal output device according to claim 1.
The sound leakage elimination signal adding means is
A result obtained by multiplying the second channel audio signal, which is a digital signal, by a first reduction ratio corresponding to the second sound leakage ratio is added to the first channel audio signal, which is a digital signal, and the added signal Means for converting the signal into an analog signal and outputting it to the output terminal of the first channel audio signal
A result obtained by multiplying the first channel audio signal, which is a digital signal, by a second reduction ratio corresponding to the first sound leakage ratio is added to the second channel audio signal, which is a digital signal, and the added signal Means for converting the signal into an analog signal and outputting it to the output terminal of the second channel audio signal
Audio signal output device comprising a. The audio signal output device according to claim 4.
Means for changing the first reduction ratio and / or the second reduction ratio in response to a user operation input
Audio signal output device. The audio signal output device according to claim 4.
The sound leakage elimination signal adding means is
A first delay means for delaying the second channel audio signal, which is a digital signal, before or after multiplying the second channel audio signal, which is a digital signal, by the first reduction ratio; And second delay means for delaying the first channel audio signal, which is the digital signal, before or after multiplying the first channel audio signal by the second reduction ratio.
Audio signal output device. The audio signal output device according to claim 6.
The first delay means and the second delay means are variable delay means, and the amount of delay of the first delay means and / or the second delay means is variable in response to a user operation input. Be controlled
Audio signal output device. The three extreme terminals include a first channel audio signal output terminal, a second channel audio signal output terminal, and a ground terminal common to the first channel audio signal and the second channel audio signal. When the external terminal corresponding to the child is connected, sound leakage of the second channel audio signal to the first sound reproduction unit for sound reproduction of the first channel audio signal connected to the external terminal, and / or Alternatively, it is a method of reducing sound leakage of the first channel audio signal to a second sound reproduction unit that reproduces sound of the second channel audio signal by signal processing means in an audio signal output device having the three-pole terminal. And
The signal processing means reduces the first channel audio signal according to a second sound leakage ratio when the second channel audio signal leaks to the first sound reproduction unit via the common ground terminal. A second channel audio signal is added and supplied to the output terminal of the first channel audio signal, and the first channel audio signal is connected to the second channel audio signal via the common ground terminal. The first channel audio signal reduced in accordance with the first sound leakage ratio when leaking to the second sound reproduction unit is added and supplied to the output terminal of the second channel audio signal.
Sound leakage reduction method. The sound leakage reduction method according to claim 8,
The signal processing means determines a reduction amount of the second channel audio signal to be added to the first channel audio signal and a reduction amount of the first channel audio signal to be added to the second channel audio signal in accordance with a user operation input. And a variable control process
Sound leakage reduction method. The sound leakage reduction method according to claim 8,
The signal processing means includes
Delaying the second channel audio signal to be added to the first channel audio signal before or after the reduction;
Delaying the first channel audio signal to be added to the second channel audio signal before or after the reduction.
Sound leakage reduction method. The sound leakage reduction method according to claim 10,
The signal processing means operates a user operation on a delay amount of the second channel audio signal to be added to the first channel audio signal and / or a delay amount of the first channel audio signal to be added to the second channel audio signal. A step of variably controlling according to input is provided.
Sound leakage reduction method.

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