JP4149458B2 - Wireless microphone receiver characterized by output switch control - Google Patents

Description

  The present invention relates to a howling prevention technique in a wireless microphone receiver, and more particularly, to a novel technique focusing on the distance between a wireless microphone and a speaker.

Various techniques for preventing howling in a loudspeaker are known. For example, Japanese Patent Laid-Open No. 8-130792 discloses a technique for predicting and suppressing a frequency band in which howling occurs by measuring a frequency characteristic of sound. Japanese Patent No. 2773656 discloses a technique for detecting howling by using a notch filter that detects a frequency band in which howling occurs and attenuates only the gain of the band.
Japanese Patent Laid-Open No. 8-130792 Japanese Patent No. 2773656

  With any conventional howling prevention technology, when a microphone is brought extremely close to a speaker, acoustic vibrations from the speaker are largely input to the microphone, and thus it is difficult to prevent howling.

A typical wireless microphone transmits a signal having an electromagnetic wave such as a microwave or infrared rays as a carrier wave. In the former type, the microwave antenna is a radio signal supplementer, and in the latter type, the infrared sensor is a radio signal supplementer. In any type, the closer the wireless microphone that emits the transmission signal is to the wireless signal supplement device (an antenna or an infrared sensor, which is representatively an antenna), the greater the reception intensity of the antenna. That is, the smaller the distance between the antenna and the wireless microphone, the higher the reception strength by the antenna.
The inventor of this application pays attention to the above facts, and if the antenna of the wireless microphone receiver is installed on the speaker side, the reception strength by the antenna increases as the distance between the speaker and the wireless microphone decreases. I thought. This idea was developed to create the present invention.

A wireless microphone receiver according to the present invention includes a wireless signal capturing device that captures a wireless signal from a wireless microphone, a receiving circuit that demodulates the captured wireless signal and outputs an audio signal, and an output path of the receiving circuit. A reception intensity detection circuit for detecting the reception intensity of the radio signal captured by the intervening output switch and the radio signal capturing device, a non-volatile memory for storing the large level reference value, means for variably setting the large level reference value, and detection an output switch control circuit for turning off the output switch when the reception intensity is higher than the atmospheric level reference values, a howling detection circuit, and the initialization switch, I der that a operation mode control unit, The following matters (1) to (5) are provided.
(1) The howling detection circuit detects the occurrence of howling by analyzing the audio signal of the receiving circuit.
(2) The initialization switch must be able to specify the initialization mode.
(3) The operation mode control means performs the initialization mode when the designation of the initialization mode is input, and otherwise performs the normal mode.
(4) In the initialization mode, when the howling detection circuit detects howling, the reception intensity data detected by the reception intensity detection circuit is written to the nonvolatile memory.
(5) In the normal mode, the output switch is turned off when the reception intensity detected by the reception intensity detection circuit exceeds the reception intensity data stored in the nonvolatile memory.

  In the present invention, the switch control circuit may turn off the output switch when the detected reception intensity falls below the small level reference value.

  In the above invention, the radio signal capturing device is a microwave antenna and may be connected to the apparatus main body via an antenna cable.

  When the wireless microphone is brought close to the radio signal capturing device of the wireless microphone receiver of the present invention, the reception intensity detected by the reception intensity detection circuit exceeds the large level reference value, so that the output switch is turned off. Therefore, howling can be effectively prevented by arranging the radio signal capturing device near the speaker.

  In addition, when the wireless microphone is moved away and the output switch is turned off when the reception intensity detected by the reception intensity detection circuit falls below the low level reference value, the squelch function works effectively to reduce noise. Can be cut.

=== First Embodiment ===
FIG. 1 shows the appearance of a wireless microphone according to an embodiment of the present invention, and FIG. 2 shows the electrical system configuration. The apparatus of this embodiment receives a microwave radio signal emitted from a wireless microphone 1, and performs diversity reception by two antennas 2. As shown in FIG. 1, the main body 30 of the receiving device is configured by a substantially rectangular parallelepiped case, and the two antennas 2 are connected to the main body 30 by thin cables 31, respectively. It is possible to install at a position different from 30 installation positions. A power plug 32 connected to a commercial power outlet is pulled out from the main body 30 with a cable, and an audio signal output plug 33 for guiding an audio signal demodulated from a received signal of the wireless microphone 1 to an external device is a cable. Has been pulled out.

  The main body 30 includes the diversity reception circuit 3, the output switch 4, the signal level detection circuit 5, the initialization switch 7, the howling detection circuit 8, the noise level detection circuit 9, the microcomputer 6 and the like shown in FIG. Built in.

  Two antennas 2 are connected to the diversity receiving circuit 3, and an antenna reception signal having a better reception state (with a higher reception intensity) is selected and demodulated. The output switch 4 is interposed between the audio signal output terminal of the diversity receiving circuit 3 and the connection terminal of the audio signal output plug 33, and is turned on / off by the microcomputer 6. The signal level detection circuit 5 detects the reception strengths of the two antennas 2 and inputs the detection signals to the microcomputer 6.

  The howling detection circuit 8 sequentially analyzes the frequency of the audio signal to monitor the presence or absence of howling in an initialization mode to be described later, and inputs it to the microcomputer 6 when the occurrence of howling is detected. The noise level detection circuit 9 detects the noise level of the audio signal and inputs it to the microcomputer 6 in the initialization mode. The initialization switch 7 inputs a control signal that instructs activation of the initialization mode to the microcomputer 6.

  When receiving the reception intensity data, the microcomputer 6 selects the larger reception intensity data and compares it with the large level reference value and the small level reference value stored in the memory. If the received intensity data exceeds the large level reference value, the microcomputer 6 turns off the output switch 4. A control signal for turning off the output switch 4 is also output when the received intensity data is below the low level reference value. If the received intensity data is between the small level reference value and the large level reference value, the output switch 4 is turned on.

=== Use in karaoke equipment ===
FIG. 3 shows an example in which the first embodiment apparatus shown in FIGS. 1 and 2 is used in a karaoke apparatus. The karaoke apparatus has a well-known configuration, and includes a main computer 11, a hard disk device 12, an operation / display panel unit 13, a video memory 14, a display processing unit 15, a display device 16, a communication control unit 17, a performance processing unit 18, and a mixing amplifier. 19. Two speakers 10 including a wireless port 23, a portable computer 24, and a stereo system.

  The two speakers 10 are installed at positions separated from each other, and are connected to a stereo audio output terminal of a mixing amplifier 19 included in the karaoke apparatus body. The main body 30 of the wireless microphone receiver according to the first embodiment described above is installed on the side of the karaoke apparatus main body, and connects the audio signal output plug 33 to the microphone input terminal of the karaoke apparatus main body. The two antennas 2 are each pulled out from the receiving apparatus main body 30 by a cable 31 and arranged near the front of the two speakers 10.

=== Operation as a karaoke loudspeaker ===
In the usage form of the karaoke apparatus shown in FIG. 3, when the user approaches the speaker 10 while holding the wireless microphone 1 while singing and the wireless microphone 1 and the speaker 10 approach, an antenna installed in the vicinity thereof. 2 increases the intensity of the carrier wave of the wireless microphone 1 received. If any of the reception strengths detected by the signal level detection circuit 5 exceeds a predetermined large level reference value (described later) stored in an appropriate non-volatile memory, the microcomputer 6 determines that the reception strength is excessive and outputs it. Switch 4 is turned off. Therefore, output to the mixing amplifier 19 is stopped, and sound emission from the speaker 10 is stopped.

  When the reception intensity from any one of the antennas 2 becomes excessive in this way, the output to the mixing amplifier 19 is stopped, so that the sound output from the speaker 10 is stopped and the occurrence of howling can be reliably prevented.

  Thereafter, when all the reception strengths received by the antenna 2 become equal to or less than the large level reference value, the output switch 4 that has been turned off is turned on again, and the output to the mixing amplifier 19 is resumed.

  Further, a squelch level (small level reference value) corresponding to the interference level under this environment is also set and stored in the memory of the wireless microphone receiver. When the reception intensity from the wireless microphone 1 decreases, the noise level increases relatively. When the strongest reception intensity falls below this squelch level, the squelch operation is applied to block the noise. When the user moves away the wireless microphone 1 and the reception intensity from the wireless microphone 1 falls below the squelch level, the output switch 4 is turned off to prevent noise from being output. Accordingly, the squelch operation works properly without being excessively effective, and environmental noise can be effectively cut.

=== Initialization mode ===
There are various possible methods for setting the large level reference value that makes the reception intensity from the antenna 2 excessive. In the present embodiment, the operation mode can be switched to the initialization mode in addition to the normal mode described above, and the large level reference value is determined in the initialization mode and stored in a suitable non-volatile memory. ing. An initialization switch 7 is provided for instructing the wireless microphone reception device in an initialization mode. When the initialization mode is designated and inputted by the administrator of the karaoke apparatus or the like, the microcomputer 6 determines the large level reference value by the following initialization mode processing and sets it in the memory.

  In the initialization mode, the howling detection circuit 8 sequentially analyzes the frequency of the audio signal and monitors the presence or absence of howling. An administrator who designates and inputs the initialization switch 7 gradually brings the wireless microphone 1 closer to the speaker 10. When the howling detection circuit 8 detects howling, the reception intensity detected by the signal level detection circuit 5 at that time is stored in the memory. The above operation is repeated until a specified input for ending the predetermined initialization mode is made. When howling occurs multiple times, the minimum received intensity is stored in the memory. That is, when the detected reception intensity is smaller than the value stored in the memory, it is updated and stored.

  The large level reference value determined in this manner may be a value common to all the speakers 10 when a plurality of speakers 10 are installed, or may be set individually for each speaker 10. . Each set value may be stored in the memory in association with the identification information of the speaker 10 as appropriate. When the large level reference value is individually set, whether or not the reception intensity is excessive is determined based on the large level reference value that is different for each speaker 10 even in the normal mode.

  If a value slightly smaller than the reception intensity at the time of howling is stored in the memory, howling can be prevented more reliably.

  The squelch level setting method can also be set in the initialization mode, similarly to the setting of the large level reference value. A noise level detection circuit 9 for detecting the noise level of the audio signal demodulated by the diversity receiving circuit 3 is provided. In the initialization mode, the user moves the wireless microphone 1 away from the detected wireless microphone 1 to detect the noise level. Detect the noise level of the audio signal. When the detected noise level exceeds a specified value, the received intensity at that time is stored in the memory as a squelch level.

=== Other technical matters ===
A plurality of output switches 4 may be provided corresponding to each of the plurality of speakers 10. For example, a plurality of antennas 2 corresponding to each of the speakers 10 are installed, and the output switch 4 for each speaker 10 is turned on / off based on the reception intensity individually detected by each antenna 2.

  When starting the initialization mode, a predetermined default value is stored in the memory in advance. A large level reference value capable of preventing howling in a general environment and a squelch level at which a sufficient squelch operation can be applied are set (so as not to be too small). The default value may be rewritten only when the memory value set / updated when the initialization mode is activated last time is smaller than the default value.

  As a method for specifying the end of the initialization mode, for example, the initialization switch 7 may be pressed again. Alternatively, when the automatic reset type initialization switch 7 provided in the wireless microphone 1 is pressed with a finger, an initialization mode instruction input may be considered, and when the finger is released, the initialization mode end instruction input may be considered.

  As another method for determining the large level reference value, the reference value may be variably set in conjunction with the set value of the volume adjustment of the wireless microphone 1. That is, when the user can adjust the volume of the wireless microphone 1 with the wireless microphone receiver and the microphone volume is set to be large, howling is likely to occur near the speaker 10, so that the large level reference Set the value to a lower value. On the contrary, when the volume is set low, howling does not easily occur even when the speaker 10 is approached, so that the large level reference value can be set to be inversely large.

  In addition, the wireless microphone receiver according to the present invention is not limited to the form connected to the karaoke apparatus. Of course, the present invention can be applied in a form in which the wireless microphone receiver is connected to one or many speakers 10 via an amplifier. For example, in a conference room where a large number of speakers 10 are installed, howling is performed when a person with the wireless microphone 1 walks around by installing the antenna 2 of the wireless microphone receiver according to the present invention in the vicinity of each speaker 10. Can be effectively prevented.

=== Second Embodiment ===
FIG. 4 shows the appearance of a receiving apparatus according to the second embodiment of the present invention. This embodiment is an infrared wireless microphone receiving apparatus, and a light receiving dome 41 of an infrared sensor that supplements an infrared radio signal emitted from the wireless microphone is integrally disposed on the front surface of the apparatus main body 30. Although this embodiment is different from the first embodiment of the diversity reception system because there is one radio signal capturing device, the circuit configuration and functions that are the gist of the present invention are the same as those of the first embodiment, and the description thereof will be omitted. In the case of the apparatus of the second embodiment, if the power amplifier such as a karaoke apparatus and the receiving apparatus main body 30 are connected with a sufficiently long cable and the apparatus main body 30 is disposed in the vicinity of the speaker 10, the above-described implementation is performed. The effect is similar to the example.

  Only the light receiving dome portion of the infrared sensor can be unitized and pulled out with a sufficiently long cable. Then, only the infrared sensor that supplements the infrared radio signal emitted from the wireless microphone can be disposed in the vicinity of the speaker 10, and the circuit configuration and functions similar to those of the first embodiment including the configuration of the diversity reception method are the infrared The same effect as in the first embodiment can be obtained.

1 is an external perspective view of a wireless microphone receiver according to a first embodiment. It is a functional block diagram of an apparatus same as the above. It is a functional block diagram of the karaoke apparatus using the same apparatus. It is an external appearance perspective view of the wireless microphone receiver which concerns on 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wireless microphone 2 Antenna 3 Diversity receiving circuit 4 Output switch circuit 5 Signal level detection circuit 6 Microcomputer 7 Initialization switch 8 Howling detection circuit 9 Noise level detection circuit 10 Speaker 19 Mixing amplifier 31 Antenna cable 41 Infrared sensor

Claims (1)

A radio signal capturing device that captures a radio signal from a wireless microphone, a receiving circuit that demodulates the captured radio signal and outputs an audio signal, an output switch that is interposed in an output path of the receiving circuit, and a radio signal capturing device A reception strength detection circuit for detecting the reception strength of the captured radio signal, a non-volatile memory for storing a large level reference value, a means for variably setting the large level reference value, and a detected reception strength that is a large level reference value. A wireless microphone receiver comprising an output switch control circuit that turns off the output switch when exceeded, a howling detection circuit, an initialization switch, and an operation mode control means,
The howling detection circuit analyzes the audio signal of the receiving circuit to detect howling,
The initialization switch can be used to specify the initialization mode.
The operation mode control means performs the initialization mode when the designation of the initialization mode is input, otherwise performs the normal mode,
In the initialization mode, when the howling detection circuit detects howling, the reception intensity data detected by the reception intensity detection circuit is written to the nonvolatile memory.
The normal mode turns off the output switch when the reception intensity detected by the reception intensity detection circuit exceeds the reception intensity data stored in the nonvolatile memory.

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