JP2018098704A - Howling prevention method during hands-free speech - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a howling prevention method in which a complex processing for determining the occurrence of a howling at high accuracy is not required.SOLUTION: A howling prevention method in a telephone device comprising a hands-free speech function, includes: a specific frequency control step of controlling a signal level of a specific frequency band of a sound signal; and a present sound determination step of determining whether or not the telephone device is a transmitting side. In the case where it is determined that the telephone device is the transmitting side, the signal level of the specific frequency band of the sound signal reproduced by the speaker is reduced to a predetermined value or less for transmission. In the case where it is determined that the telephone device is not the transmitting side, the signal level of the specific frequency band inputted from the microphone is reduced to the predetermined value or less for transmission.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a howling prevention method in a telephone device having a hands-free call function.

  The cause of howling that occurs in a telephone device having a hands-free call function is that a part of the received voice reproduced by the speaker of the partner device is input to the microphone of the partner device, returns to the own device, and is reproduced from the speaker of the own device. This is because a part of the signal is input to the microphone of the own device and transmitted again to the partner device, and by repeating this, a specific frequency at which the phase of the audio signal matches with the propagation delay oscillates as positive feedback. Therefore, howling can be prevented by removing a specific frequency for positive feedback from the transmitted voice or received voice. As a specific method of preventing this howling, the amplitude of the audio signal input from the microphone is measured, and when it is determined that howling has occurred, the amplitude of the audio signal output to the speaker is attenuated, Alternatively, there is a method of suppressing the occurrence of howling by reducing the amplitude of a specific frequency band of the audio signal (for example, Patent Document 1).

  However, in the technique described in Patent Document 1, after determining that howling has occurred, subsequent howling is suppressed, so that howling occurs momentarily. Further, the process of determining whether or not howling has occurred with high accuracy is complicated.

Japanese Patent Publication No. 2011-114758

  Accordingly, an object of the present invention is to provide a howling prevention method that does not require complicated processing for determining howling.

  In order to solve the above-mentioned problem, the present invention is a method for preventing howling in a telephone device having a hands-free call function, which is input from an audio signal reproduced by a speaker provided in the telephone device or a microphone provided in the telephone device. A specific frequency control step for controlling a signal level in a specific frequency band that induces howling included in an audio signal, and an audio signal input from the microphone or an audio signal received from a communication partner side are analyzed and the telephone device transmits An audio signal reproduced by the speaker when the specific frequency control step determines that the telephone device is the transmitting side. When the signal level of the specific frequency band is reduced to a predetermined value or less, and the telephone device is determined not to be the transmitting side, And transmits to reduce the signal level of the specific frequency band of the input audio signal below a predetermined value from.

  According to the present invention, since complicated processing for determining occurrence of howling is unnecessary, processing is simple and economical. Moreover, when the telephone device to which the present invention is applied is the transmitting side, the signal level of the specific frequency band of the audio signal reproduced by the speaker of the telephone device is only reduced, so that the audio signal to be transmitted to the other telephone device can be reduced. There is an effect that the frequency characteristics are not impaired.

  In addition, when the telephone device is the receiver side, it only reduces the signal level of a specific frequency band of the voice signal input from the microphone of the telephone device, so the frequency characteristics of the voice signal reproduced by the speaker of the telephone device are There is an effect that it is not damaged. Therefore, as long as conversation is performed between the telephone device and the communication destination telephone device in a half-duplex state in which transmission is performed alternately, the frequency characteristics of the transmitted voice and received voice are not impaired, and natural conversation is possible. is there.

  Furthermore, when talking in full-duplex state in which the own telephone device and the communication destination telephone device are talking at the same time, only the signal level in the specific frequency band is reduced, so the beginning sound is missing at the start of the conversation. There is no hindrance to the conversation itself.

The internal block block diagram of the telephone apparatus which concerns on embodiment of this invention Flowchart of an operation during a hands-free call according to an embodiment of the present invention

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an internal block diagram of a telephone device (hereinafter abbreviated as this device) 1 to which the present invention is applied. The device 1 is a telephone device having a hands-free calling function, for example, a general telephone terminal, an extension telephone terminal of a button telephone system, a telephone terminal of a teleconference device, etc. It has a call function.

  The apparatus 1 includes a control unit 10, a microphone 11, a transmission signal amplification unit 12, a transmission level determination unit 13, a transmission filter 14, a changeover switch 15, a communication unit 16, a reception signal amplification unit 17, and a reception level determination unit 18. , Receiving filter 19, changeover switch 20, speaker 21, setting information storage unit 22, display unit 23, and operation unit 24. In addition, the thick line in a figure has shown the flow of the audio | voice signal.

  The control unit 10 is means for controlling each unit of the apparatus 1, and in particular controls switching of the changeover switches 15 and 20 according to signals input from the transmission level determination unit 13 and the reception level determination unit 18. The operation flow of the control unit 10 will be described later. The control unit 10 also performs the original functions as a general telephone terminal, an extension telephone terminal of a button telephone system, and a communication conference apparatus, but detailed description thereof is omitted.

  The microphone 11 is means for inputting a voice uttered by a speaker existing in the vicinity of the apparatus 1, converting the voice into a voice signal, and outputting the voice signal to the transmission signal amplification unit 12.

  The transmission signal amplifying unit 12 is means for amplifying the audio signal input from the microphone 11 to an appropriate level based on the control from the control unit 10 and outputting the amplified signal to each block in the subsequent stage.

  The transmission level determination unit 13 receives the voice signal output from the transmission signal amplification unit 12 and is set in advance as a transmission level corresponding to the volume level of the voice uttered by a speaker existing in the vicinity of the apparatus 1. This is means for notifying the control unit 10 of the determination result of the magnitude relationship in comparison with the transmission reference level.

  The transmission filter 14 is means for filtering the voice signal input from the transmission signal amplification unit 12 and outputting the filtered signal to the changeover switch 15. Here, the filtering characteristic is a characteristic that reduces the signal level of a specific frequency band that induces howling to a level that does not induce howling. The specific frequency band is specified and the level of reduction is controlled by the control unit 10. based on.

  The changeover switch 15 is a means for outputting either of the audio signals input to the A system and the B system to the communication unit 16 based on the control from the control unit 10.

  The communication unit 16 is means for communicating with a communication partner via various communication networks (not shown) such as a telephone network, a mobile phone network, a data communication network, etc., and exchanging a transmission voice signal and a reception voice signal.

  The reception signal amplification unit 17 is a unit that amplifies the audio signal input from the communication unit 16 to an appropriate level based on the control from the control unit 10 and outputs the amplified signal to each block in the subsequent stage.

  The reception level determination unit 18 monitors the audio signal output from the reception signal amplification unit 17 and compares the reception level corresponding to the volume level of the audio signal received from the communication partner side with a preset reception reference level. This is means for notifying the control unit 10 of the determination result of the magnitude relationship.

  The reception filter 19 is means for filtering the voice signal input from the reception signal amplification unit 17 and outputting the filtered signal to the changeover switch 20. Here, the filtering characteristic is a characteristic that reduces the signal level of a specific frequency band that induces howling to a level that does not induce howling. The specific frequency band is specified and the level of reduction is controlled by the control unit 10. based on.

  The changeover switch 20 is a means for outputting either of the audio signals input to the A system and the B system to the speaker 21 based on the control from the control unit 10.

  The speaker 21 is means for converting the sound signal input from the changeover switch 20 into air vibration as sound and outputting it.

  The setting information storage unit 22 stores various data such as a transmission reference level in the transmission level determination unit 13, a reception reference level in the reception level determination unit 18, parameters for controlling the filtering characteristics of the transmission filter 14 and the reception filter 19, and the like. It is means for storing these data and exchanging these data with the control unit 10.

  The display unit 23 is a means for displaying various information input from the control unit 10, and various display devices such as an LCD (Liquid Crystal Display) and an EL (Electro-Luminescence) can be applied.

  The operation unit 24 is means for outputting key operation information for operating the apparatus 1 to the control unit 10, and various input devices such as a numeric keypad and a touch panel are applicable.

  FIG. 2 is an operation flowchart of the apparatus 1 in a hands-free call. Hereinafter, the operation flow of the apparatus 1 will be described with reference to FIG. This flow starts from a state in which the hands-free call function is activated (S200), and in the standby state, each NO in S210, S220, and S230 is circulated and waits for the occurrence of each event. A description of general functions as a telephone terminal, a telephone terminal, an extension telephone terminal of a key telephone system, a communication conference apparatus, and the like is omitted.

  In S210, the control unit 10 monitors the determination result notified from the transmission level determination unit 13, and the level of the transmission voice signal output from the transmission signal amplification unit 12 is stored in the setting information storage unit 22. If it is equal to or higher than the transmission reference level (YES in S210), the changeover switch 15 and changeover switch 20 are switched to the A side (S211), and the process proceeds to S220. If NO in S210, S211 is skipped and the process proceeds to S220.

  Here, the determination that the volume level of the transmitted voice signal is equal to or higher than the transmission reference level is that a voice from a speaker existing in the vicinity of the apparatus 1 is detected, and a person on the apparatus 1 side is detected. Is in a state of speaking. In this state, since the changeover switch 15 is on the A side, the transmission voice signal transmitted to the communication partner side does not pass through the transmission filter 14, so that the signal level in the specific frequency band is not reduced. As a result, the communication partner reproduces the sound from the apparatus 1 with a natural sound quality.

  In this state, since the changeover switch 20 is also on the A side, the reception voice signal received from the communication partner side passes through the reception filter 19, so that the signal level in the specific frequency band is reduced. As a result, even if the transmitted voice signal transmitted to the communication partner side returns to the present apparatus 1 (echo) and is reproduced by the speaker 21, the signal level in the specific frequency band that induces howling is reduced. Can be prevented.

  That is, when the changeover switch 15 and changeover switch 20 are in the A side, a half-duplex call in which a person on the apparatus 1 side is speaking and a person on the communication partner side is listening to a statement from the apparatus 1 side. This is a state, and howling can be prevented without impairing voice quality.

  Even if the person on the apparatus 1 side is speaking, it is also assumed that the person on the communication partner side speaks. In this case, since the changeover switch 20 is in the A side state, the received voice signal passes through the reception filter 19, so that the voice quality of the received voice reproduced by the speaker 21 deteriorates as much as the signal level in the specific frequency band is reduced. To do. However, the content of the voice is generally a speech for the purpose of interrupting the speech of the person on the apparatus 1 side, and even if the voice quality is somewhat deteriorated, it does not cause a big trouble in the conversation itself.

  In S <b> 220, the control unit 10 monitors the determination result notified from the reception level determination unit 18, and the level of the reception voice signal output from the reception signal amplification unit 17 is stored in the setting information storage unit 22. When it is determined that the level is higher than the level (S220, YES), the selector switch 15 and the selector switch 20 are switched to the B side (S221), and the process proceeds to S230. If NO in S220, S221 is skipped and the process proceeds to S230.

  Here, the determination that the volume level of the received voice signal is higher than the reference level is that a received voice signal higher than the reference level has been detected from the communication partner side, and the person on the communication partner side is speaking. is there. In this state, since the changeover switch 20 is on the B side, the reception voice signal received from the communication partner side does not pass through the reception filter 19 and the signal level in the specific frequency band is not reduced. As a result, the voice from the communication partner side is reproduced by the speaker 21 with natural sound quality.

  In this state, since the changeover switch 15 is also on the B side, the transmission voice signal transmitted to the communication partner side passes through the transmission filter 14, and the signal level of the specific frequency band is reduced. As a result, even when the sound reproduced by the speaker 21 returns to the communication partner side through the microphone 11, the signal level in the specific frequency band that induces howling is reduced, and thus howling can be prevented.

  That is, the state where the changeover switch 15 and the changeover switch 20 are on the B side is a half-duplex call state in which a person on the communication partner side is speaking and a person on the device 1 side is listening to a message from the communication partner side. Thus, howling can be prevented without impairing voice quality.

  In addition, even if it is in the state which is listening to the speech from the communication other party side, the speech of the person on this device 1 side is also assumed. In this case, since the changeover switch 15 is in the B side, the transmission voice signal passes through the transmission filter 14 and the voice level of the transmission voice signal transmitted to the communication partner side is reduced by the amount of the signal level of the specific frequency band reduced. Quality deteriorates. However, the content of the speech is generally a speech that interrupts the speech of the person on the other end of the communication, and even if the speech quality is somewhat deteriorated, it does not cause a major hindrance to the conversation itself.

In S230, when operations related to various level adjustments are performed from the operation unit 24 (S230, YES), the amplification factor of the transmission signal amplification unit 12, according to the operation content from the operation unit 24,
The amplification factor of the reception signal amplification unit 17, the filter specification of the transmission filter 14, the filter specification of the reception filter 19, the transmission reference level compared with the transmission level determination unit 13, the reception reference level compared with the reception level determination unit 18, etc. Are adjusted (S231), and the process returns to S210.

  Although not shown, in the level adjustment in S230, the adjustment of the amplification factor of the transmission signal amplification unit 12, the amplification factor of the reception signal amplification unit 17, the filter specification of the transmission filter 14, and the filter specification of the reception filter 19 are howling. It is also possible to automatically adjust by adding an automatic detection function and a filter characteristic automatic adjustment function (for example, applying a part of the technique described in Patent Document 1).

  Here, since the specific frequency band that induces howling depends on the acoustic environment on the device 1 side and the acoustic environment on the communication partner side, the data of each level adjustment stored in S230 is stored in association with each communication partner. You may do it.

  The embodiment of the present invention has been described above. According to the present embodiment, since complicated processing for determining occurrence of howling is unnecessary, processing is simple and economical. In addition, when the device 1 is on the transmitting side, the frequency characteristics of the audio signal to be transmitted to the other telephone device are only reduced by reducing the signal level of the specific frequency band of the audio signal reproduced by the speaker 21 of the device 1. There is an effect that it is not damaged.

  Further, when the apparatus 1 is the receiver side, it only reduces the signal level of the specific frequency band of the audio signal input from the microphone 11 of the apparatus 1, so the frequency of the audio signal reproduced by the speaker 21 of the apparatus 1 is reduced. There is an effect that the characteristics are not impaired. Therefore, as long as conversation is performed in a half-duplex state in which the apparatus 1 and the communication partner alternately transmit, the frequency characteristics of the transmitted voice and the received voice are not impaired, and natural conversation is possible.

  Furthermore, even in the case of a conversation in the full duplex state where the apparatus 1 and the communication partner are talking at the same time, since the signal level of the specific frequency band is only reduced, there is no omission at the beginning of the conversation, and the conversation itself There is no hindrance. Therefore, the present invention is extremely suitable for a device having a hands-free call function, such as a general telephone terminal, an extension telephone terminal of a key telephone system, and a communication terminal of a communication conference apparatus.

DESCRIPTION OF SYMBOLS 1 ... Telephone apparatus 10 ... Control part 11 ... Microphone 12 ... Transmission signal amplification part 13 ... Transmission level determination part 14 ... Transmission filter 15 ... Changeover switch 16 ..Communication unit 17 ... received signal amplification unit 18 ... received level determination unit 19 ... received filter 20 ... switch 21 ... speaker 22 ... setting information storage unit 23 ... display Unit 24 ... operation unit

Claims (1)

A method for preventing howling in a telephone device having a hands-free call function,
A specific frequency control step for controlling a signal level of a specific frequency band that induces howling included in an audio signal reproduced by a speaker included in the telephone device or an audio signal input from a microphone included in the telephone device; and from the microphone Analyzing a voice signal to be input or a voice signal received from a communication partner side and determining whether or not the telephone device is a transmitter side;
The specific frequency control step reduces the signal level of the specific frequency band of the audio signal reproduced by the speaker to a predetermined value or less when it is determined that the telephone device is a transmitting side, and the telephone device transmits A method for preventing howling during a hands-free call, wherein the signal level of the specific frequency band of the audio signal input from the microphone is reduced to a predetermined value or less when it is determined that it is not the speaker side.

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