JP3295100B2 - Sound equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic device which is arranged in a room having a relatively limited space, such as a vehicle interior.

[0002]

2. Description of the Related Art As is well known, when a user listens to a reproduced sound of an acoustic device in a room where space is relatively limited, for example, in a vehicle, the vehicle interior has a direct sound of the reproduced sound.
This direct wave is reflected by a glass surface or the like that interrupts the course of the wave to generate a reflected wave. When the reflected wave returns to the acoustic device side, it is reflected on a glass surface or the like on the device side and travels again in the same direction as the traveling direction of the reproduced sound.

[0003] A reciprocating loop of the sound wave in the traveling direction is formed depending on the traveling direction of the sound wave of the reproduced sound, the arrangement direction of each of the glass surfaces positioned before and after the direction, and the interval between them. It is known that a so-called standing wave having a frequency inversely proportional to the distance between the glass surfaces is generated when the traveling wave and the reflected wave interfere with each other. For example, in an actual vehicle cabin, when an acoustic signal is reproduced by an acoustic device, sound waves of the reproduced sound are reflected by front, rear, left and right window glasses and the like, and several standing waves having different frequencies are generated.

[0004]

When the standing wave is generated, the sound pressure level differs in the same room depending on the location of the peak or valley of the standing wave. May be exerted. Further, with respect to the frequency characteristics of the sound entering the listener's ear, there is a problem that the sound pressure level becomes uneven at each frequency, and the sound quality is impaired.

[0005] The standing wave is generated when the phase of the traveling wave of the reproduced sound and the phase of the reflected wave overlap with each other, and a reciprocating loop of the sound wave is formed in these traveling directions. Therefore, for example, the same sound is delayed little by little and then further modulated and reproduced, so that the phase of the traveling wave of the reproduced sound and its reflected wave are shifted so that the phases do not easily overlap each other. Thereby, generation of a standing wave can be suppressed.

Also, when the same sound arrives at the listener's ear from several directions or a little bit later,
It is known that a so-called Haas effect occurs in which the sound that arrives first has a strong impression, but does not remain as impressive as the sound that arrives late. Therefore, if the same sound is delayed and played back after being modulated little by little, the modulation degree of the sound that reaches the ears of the listener earliest should be set as small as possible.
It is possible to leave the impression of a sound closer to the original sound as strong as possible and to prevent the sound quality perceived by the listener from changing as much as possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an acoustic wave capable of suppressing generation of a standing wave by shifting the phase of a traveling wave of a reproduced sound and each reflected wave thereof from each other. The main purpose is to provide a device.

[0008]

Therefore, a first aspect of the present invention provides an audio signal source, a delay unit for delaying a signal obtained from the signal source by a plurality of delay systems having different delay times,
Modulation means for frequency-modulating the acoustic signal delayed by the delay means at a predetermined frequency, and reproduction means for synthesizing and reproducing each acoustic signal modulated by the modulation means and delayed by the delay means; It is provided with.

According to a second aspect of the present invention, an acoustic signal source, delay means for delaying a signal obtained from the signal source by a plurality of delay systems having different delay times, and delay by the delay means are provided. A plurality of modulating means for modulating the frequency of each acoustic signal with different modulation degrees, and a reproducing means for synthesizing and reproducing each of the modulated acoustic signals are provided, and the larger the delay time is, the larger the modulation degree is. It is as if it had been set.

[0010]

According to the first aspect of the present invention, since the delay means, the modulation means, and the reproduction means are provided, the frequency is modulated at a predetermined frequency and the signals are delayed by a plurality of delay systems having different delay times. The obtained acoustic signals can be synthesized and reproduced. That is, each acoustic signal included in the reproduced sound is frequency-modulated and delayed with a different delay time, that is, reproduced in a state where the phase is shifted. Therefore, by synthesizing and reproducing these, it becomes difficult for the traveling wave and the reflected wave of the reproduced sound to overlap each other in phase. As a result, generation of a standing wave can be effectively suppressed.

According to the second aspect of the present invention, since the delay means, the modulation means, and the reproduction means are provided, the modulation degree is changed after being delayed by a plurality of delay systems having different delay times. The frequency-modulated sound signals can be synthesized and reproduced. That is, since each sound signal included in the reproduced sound is reproduced in a state where the phase is shifted according to the difference in the delay time and the difference in the modulation degree, the sound is reproduced by synthesizing the reproduced signals. The phase of the traveling wave and the phase of the reflected wave are less likely to overlap each other. As a result, generation of a standing wave can be suppressed more effectively. Also, since the modulation degree is set to be larger for a system with a longer delay time, an audio signal having a smaller modulation degree and closer to the original signal from the acoustic signal source is reproduced with a shorter delay time. Therefore, the sound closest to the original sound reaches the listener's ear earliest and leaves the strongest impression, so that the sound quality felt by the listener can be prevented from changing as much as possible.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention applied to, for example, an acoustic device for a vehicle will be described in detail with reference to the accompanying drawings. FIG. 1 is a device configuration diagram schematically showing an overall configuration of a vehicular acoustic apparatus 1 according to the present embodiment. In this figure, an acoustic signal source 2 includes, for example, an FM /
The audio signal output from the signal source 2 is first input to the filter processing unit 3. The audio signal output from the signal source 2 is configured by an apparatus such as an AM tuner, a cassette tape recorder, or a compact disk player. The filter processing unit 3 includes a low-pass filter L that passes only low-frequency components equal to or lower than a predetermined frequency.
PF and a band-pass filter B that passes only a predetermined frequency band component on a relatively high frequency side above the predetermined frequency.
PF.

In this embodiment, it is possible to prevent the generation of a low-frequency standing wave corresponding to, for example, a muffled sound when the acoustic device 1 reproduces an acoustic signal and emits the acoustic signal in the vehicle interior. For the purpose, on the downstream side of the low-pass filter LPF, a delay processing unit 4 for delaying the audio signal passing through the filter LPF, and each of the audio signals delayed by the delay processing unit 4, for example, an audio frequency band. A modulation processing unit 5 that performs frequency modulation at the following predetermined modulation frequency is provided. Note that the acoustic signal that has passed through the band-pass filter BPF is directly input to the adder 7.

[0014] The delay processing section 4, the delay time is a plurality of delay circuits D ₁ respectively different, D _2, ..., is constituted by Dn, these delay circuits D _1, D _2, ..., the delay time in the Dn τ ₁ , τ ₂ ,..., τ n are set so that τ ₁ <τ ₂ <. The acoustic signal filtered by the low-pass filter LPF is applied to each of the delay circuits D ₁ , D ₂ ,.
Through, for example, the curves A ₁ , A
_As indicated by ₂ and An, they are sent to the modulation processing unit 5 after being delayed by predetermined times τ ₁ , τ ₂ and τn, respectively. In FIG. 2, a curve A ₀ indicates a signal waveform of an acoustic signal transmitted without passing through the delay processing unit 4.

The modulation processing unit 5 includes a modulation circuit F corresponding to each of the delay circuits D ₁ , D ₂ ,..., Dn of the delay processing unit 4.
M _1, FM _2, ..., FMn are provided, each of these modulation circuit FM _1, FM _2, ..., the degree of frequency modulation of FMn by regulating controller 6 annexed to the modulation processing unit 5 , Dn are set to increase as the delay time of the corresponding delay circuits D ₁ , D ₂ ,..., Dn increases.

Each of the modulation circuits FM ₁ , FM ₂ ,.
In Mn, the phases of the respective modulated signals are set to be shifted from each other. The longer the delay time of the corresponding delay circuits D ₁ , D ₂ ,..., Dn, the larger the phase shift of the modulated signal with respect to the original signal. It is set to be. And
Each sound signal that has passed through the delay processing unit 4 is, for example, as shown in FIG.
Are modulated as shown by curves B ₁ , B ₂ and Bn, respectively, and sent to the adder 7. In addition, in FIG.
₀ indicates a signal waveform of an acoustic signal transmitted without passing through both the delay processing unit 4 and the modulation processing unit 5. In addition, a schematic graph showing the angular frequency of each acoustic signal that has passed through each of the modulation circuits FM ₁ , FM _2, and FMn is shown by curves C ₁ , C _2, and Cn in FIG.

The adder 7 has an audio signal transmitted through the delay processing unit 4 and the modulation processing unit 5 sequentially,
After passing through the low-pass filter LPF, each of the processing units 4
5 and the audio signal transmitted as it is without passing through both, and the audio signal transmitted directly as it passes through the band-pass filter BPF are input, and each audio signal synthesized by the adder 7 is , An amplifier 8 attached to the speaker 9
After being input to and amplified by the speaker 9, it is reproduced by the speaker 9 and sounded in the vehicle cabin.

As described above, according to the present embodiment, since the delay processing unit 4, the modulation processing unit 5, and the adder 7 are provided, for example, the low-frequency signal passing through the low-pass filter LPF is provided. After the audio signal in the frequency band is delayed by a plurality of delay systems having different delay times, the frequency-modulated audio signals can be synthesized with different modulation degrees, and the synthesized signal is amplified by the amplifier 8. After amplification, speaker 9
You can play with. Each sound signal included in the reproduced sound is reproduced in a state where the phase is shifted according to the difference in the delay time and the difference in the modulation degree. It is more difficult for the reflected wave and the reflected wave to overlap each other. As a result, the generation of standing waves can be effectively suppressed. Also, since the modulation degree is set to be larger for a system with a longer delay time, an audio signal having a smaller modulation degree and closer to the original signal from the acoustic signal source is reproduced with a shorter delay time. Therefore, the sound closest to the original sound reaches the listener's ear earliest and leaves the strongest impression, so that the sound quality felt by the listener can be prevented from changing as much as possible.

Next, the acoustic device according to the present invention
When delay processing and frequency modulation processing are applied to the signal
Of the test to confirm the effect of suppressing standing wave generation
I do. FIG. 5 shows the cabin 11 of the automobile used in the above-mentioned confirmation test.
It is a plane explanatory view which shows typically. In this test,
A speaker 12 is arranged on the rear side of the vehicle,
Along the center line in the direction from the vicinity of the rear glass 13
Divide the distance L to the vicinity of the glazing 14 by 4
5 are located at equal intervals in the vehicle longitudinal direction.
Location P₁, P_Two, P_Three, P_Four, P_FiveSet the measurement points for
Fixed point P₁, P_Two, P_Three , P_Four, P_FiveSound pickup microphone (not shown)
did. In this test, the windshield 14 and the rear were used.
The distance L from the glass 13 was 3.5 meters.

The case where the reproduced sound reproduced by the acoustic device according to the present invention is produced in the vehicle cabin, and the case where the reproduced sound reproduced by the ordinary acoustic device which does not perform the delay and modulation processing as before is produced. For each of the above measurement points P ₁ , P ₂ ,
The sound pressure levels were measured at P ₃ , P ₄ , and P ₅ , and the generation states of standing waves were compared. The test was performed by reproducing a reference signal having a frequency of 100 Hz with each of the above-described sound devices. In the sound device according to the present invention, a modulation frequency of 10 Hz and a modulation degree of 10% were used.
After performing the frequency modulation described above, the delay time was set to 0 ms, 1 ms, and 2 ms, delay processing was performed, and the obtained three waves were synthesized and reproduced.

FIG. 6 and FIG. 7 show the measurement results when reproduced by the audio device according to the present invention and the measurement results when reproduced by the conventional audio device, respectively. In these graphs, the horizontal axis represents time, and the vertical axis represents sound pressure levels at the respective measurement points P ₁ , P ₂ , P ₃ , P ₄ , P ₅ . 6 and 7, the curves S ₀ and S ₀ ′
Both show the signal waveform of the reference signal.

As can be seen from both graphs, a standing wave having a relatively large amplitude was generated at the measurement points P ₂ and P ₄ a certain time after the start of the measurement.
After the start of the measurement, when the time Ta has elapsed and the standing wave is almost stabilized, the amplitude (sound pressure level) of the standing wave at the measurement points P ₂ and P ₄ is reproduced by the acoustic device according to the present invention. If you are H ₂ and H _4, in the case of reproducing by the conventional acoustic apparatus was it is H ₂ 'and H _4'. When the sound is reproduced by the sound device according to the present invention, the amplitude of the standing wave is clearly smaller (H ₂ <H ₂ ′, H
₄ <H ₄ ′), the effect of suppressing standing wave generation by the acoustic device according to the present invention was confirmed. Incidentally, under the above test conditions, the sound pressure level of the standing wave was reduced by about 13 dB.

Although the above embodiments are all directed to audio devices for vehicles, the present invention is not limited to audio devices for vehicles, but also for other general uses such as business use and home use. Needless to say, it can be applied to

[Brief description of the drawings]

FIG. 1 is a device configuration diagram schematically showing an overall configuration of a vehicle acoustic device according to the present embodiment.

FIG. 2 is a graph showing a signal waveform of each acoustic signal that has passed through a delay processing unit of the vehicle acoustic device.

FIG. 3 is a graph showing a signal waveform of each acoustic signal that has passed through a modulation processing unit of the acoustic device for a vehicle.

FIG. 4 is a graph showing an angular frequency of each acoustic signal that has passed through the modulation processing unit.

FIG. 5 is an explanatory plan view of a vehicle cabin used in a test for confirming the effect of suppressing standing wave generation.

FIG. 6 is a graph showing a measurement result measured by the acoustic device according to the present invention in the confirmation test.

FIG. 7 is a graph showing a measurement result measured by a conventional acoustic device in the confirmation test.

[Explanation of symbols]

1 ... audio device 2 ... audio signal source 4 ... delay processing unit 5 ... modulation processor 6 ... controller 7 ... adder 8 ... amplifier 9 ... speaker D _1, D _2, Dn ... delay circuit FM _1, FM _2, FMn ... Modulation circuit τ ₁ , τ ₂ , τn ... delay time

Claims (2)

(57) [Claims] An audio signal source, delay means for delaying a signal obtained from the signal source by a plurality of delay systems having different delay times, and frequency modulation of the audio signal delayed by the delay means at a predetermined frequency An acoustic apparatus comprising: a modulating means for causing the sound signal to be modulated; and a reproducing means for synthesizing and reproducing each acoustic signal modulated by the modulating means and delayed by the delay means. 2. An acoustic signal source, delay means for delaying a signal obtained from the signal source by a plurality of delay systems having different delay times, and a modulation degree for each acoustic signal delayed by the delay means. A plurality of modulating means for differently modulating the frequency and reproducing means for synthesizing and reproducing the modulated audio signals are provided, and the modulation degree is set to be larger for a system having a larger delay time. Acoustic equipment.