JP2005176177A - Handsfree apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a handsfree apparatus capable of completely preventing the generation of howling by completely eliminating a sidetone signal. <P>SOLUTION: The handsfree apparatus can perform simultaneous two-way communication by receiving a speech reception audio signal from a line by a speech receiving line 9 via a line interface 2, and transmitting a speech transmission audio signal from a speech transmitting line 10 via the line interface 2. The apparatus has a bridge circuit in the line interface 2 which is used to receive the speech reception audio signal from the line, and to transmit the speech transmission audio signal to the line; and a sidetone monitoring section 40 for monitoring the level of a sidetone signal by inputting the speech transmission audio signal and the speech reception audio signal, and controlling the impedance of at least one side of the bridge circuit on the basis of the level of the monitored sidetone signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, a reception voice signal from a line is received by a reception line via a line interface unit, and a transmission voice signal to the line is transmitted from the transmission line via a line interface unit, thereby enabling simultaneous bidirectional communication. It relates to a possible hands-free device.

  FIG. 3 is a block diagram showing a conventional hands-free device.

  In FIG. 3, 1 is a master unit constituting the hands-free device, 2 is a voice signal (received voice signal) inputted from a line and outputted to a DSP 3 to be described later, and a voice signal (transmitted voice signal) is inputted from the DSP 3. The line interface 3 outputs the received voice signal to the line, performs signal processing and outputs the signal to the speaker 5 via the amplifier 4 and inputs the voice signal from the microphone 6 via the amplifier 7 for signal processing. A digital signal processor (DSP) that outputs to the line interface 2 as a transmission voice signal, 9 is a reception line on which the received voice signal is subjected to various processing, and 10 is a transmission voice signal on which the voice signal from the microphone 6 is subjected to various processing. The transmission line 31 is input to the line interface 2, and 31 is the side voice signal of the reception line 9 when the transmission voice signal is input. A line echo canceller 32 that outputs a pseudo side sound signal, which is a pseudo signal of a voice signal output from the transmission line 10 to the reception line 9 due to mismatch between the line interface 2 and the line, and 32 is a voice signal (line) The side tone signal subtractor 33 subtracts the pseudo side tone signal from the voice signal) and outputs a side tone subtraction signal, and 33 receives the voice signal on the reception line 9 and the voice signal on the transmission line 10 and receives the reception voice signal. (Accurately, the output voice signal of the side tone signal subtractor 32) and the transmitted voice signal (more precisely, the output voice signal of an echo signal subtractor 39 described later) are attenuated by the subtractors 34 and 35. , 36 and 37 are amplifiers, and 38 is an amplifier for inputting a voice signal from the line (more precisely, an output voice signal of the amplifier 36) and outputting a pseudo echo signal which is a pseudo signal of the echo signal. Over stick echo canceller 39 is the echo signal subtractor for outputting an echo subtraction signal by subtracting the pseudo echo signal from the audio signal including an echo signal.

  The operation of the hands-free device configured as described above will be described.

  The line audio signal input to the reception line 9 via the line interface 2 is subtracted by the side sound signal subtractor 32 and the subtractor 34 (this subtraction operation will be described in detail later). Amplified and output as sound from the speaker 5. In addition, sound including echo (including both direct sound that directly enters the microphone 6 from the speaker 5 and echo that is input to the microphone 6 when the sound from the speaker 5 is reflected by a wall or the like) is input to the microphone 6. The voice signal including the echo signal is output from the microphone 6 to the transmission line 10. At this time, in the transmission / reception attenuation rate controller 33, the sidetone subtraction signal output from the sidetone signal subtractor 32 is subtracted by the subtractor 34, and the echo subtraction signal output from the echo signal subtractor 39 is subtracted by the subtractor 35. The However, the amount of subtraction by the transmission / reception attenuation rate controller 33 is kept small so that simultaneous two-way communication via the reception line 9 and the transmission line 10 is possible.

Next, the echo canceller will be described. The acoustic echo canceller 38 inputs a line voice signal (more precisely, the output voice signal of the amplifier 36) and outputs a pseudo echo signal which is a pseudo signal of the echo signal, and the echo signal subtractor 39 outputs an echo of the amplifier 7 output. The pseudo echo signal output from the acoustic echo canceller 38 is subtracted from the audio signal including the signal to output an echo subtraction signal. The line echo canceller 31 receives an echo subtraction signal output from the echo signal subtractor 39 (more precisely, a transmission voice signal output from the amplifier 37) and outputs a pseudo side sound signal which is a pseudo signal of the side sound signal of the reception line 9. The side sound signal subtracter 32 outputs the side sound subtraction signal by subtracting the pseudo side sound signal output from the line echo canceller 31 from the line sound signal. The echo canceller is described in, for example, (Patent Document 1).
Japanese Patent Laid-Open No. 10-190533

  As described above, in the conventional hands-free device, the attenuation in the transmission / reception attenuation rate controller 33 is reduced to enable simultaneous two-way communication. However, the impedance (hereinafter, “ Due to the mismatch between the telephone impedance and the line impedance of the telephone line, the sidetone signal leaking from the transmission line 10 to the reception line 9 cannot be made zero, and howling cannot be completely prevented. It had the problem that.

  This hands-free device is required to be able to completely remove side sound signals and completely prevent howling.

  In order to satisfy this requirement, an object of the present invention is to provide a hands-free device capable of completely removing side sound signals and completely preventing howling.

  In order to achieve this object, the hands-free device of the present invention receives a received voice signal from a line on a receiving line via a line interface unit, and transmits a transmitted voice signal to the line via a line interface unit. A hands-free device capable of simultaneous two-way communication by transmitting from a line, a bridge circuit in a line interface unit for receiving a received voice signal from the line and transmitting a transmitted voice signal to the line, and a transmitted voice A side-tone monitor for controlling the impedance of at least one side of the bridge circuit based on the level of the side-tone signal monitored by inputting the signal and the received voice signal Yes.

  As a result, a hands-free device can be obtained in which the side sound signal can be completely removed and howling can be completely prevented.

  The hands-free device of the present invention simultaneously receives a received voice signal from a line via a line interface unit on a reception line and transmits a transmitted voice signal to the line from the transmission line via the line interface unit. A hands-free device capable of two-way communication, comprising: a bridge circuit in a line interface unit for receiving a received voice signal from a line and transmitting a transmitted voice signal to the line; a transmitted voice signal and a received voice signal; A side sound monitor that controls the impedance of at least one side of the bridge circuit based on the level of the monitored side sound signal and monitors the level of the side sound signal. Based on the side sound monitor, the impedance of at least one side of the bridge circuit is controlled so that the side sound signal is zero. Since it can be completely removed sidetone signal, an advantageous effect that the occurrence of howling can be completely prevented is obtained.

  Further, the side tone monitor can completely prevent the occurrence of howling by controlling the impedance of at least one side of the bridge circuit so that the level of the monitored side tone signal is lower than the level at which no howling occurs. The advantageous effect is obtained.

In addition, the side tone monitor is configured such that the impedance of one side of the bridge circuit is Z1, the impedance of the side facing one side is Z1A, the impedance of the side adjacent to one side is Z2, and the impedance of the side facing the adjacent side is Z2. By controlling the impedance of at least one side of the bridge circuit so that Z1 × Z1A = Z2 × Z2A when Z2A is set, side sound signals can be almost completely removed, thus preventing the occurrence of howling. The advantageous effect of being able to do this is obtained.

  The object of the present invention is to completely eliminate the side-tone signal and completely prevent howling, and to set the impedance of at least one side of the bridge circuit to zero based on the level of the monitored side-tone signal. It was realized by controlling so that

  In order to solve the above-mentioned problems, a first invention is to receive a received voice signal from a line on a receiving line via a line interface unit and transmit a transmitted voice signal to the line via the line interface unit. A hands-free device capable of simultaneous two-way communication by transmitting from a line, a bridge circuit in a line interface unit for receiving a received voice signal from the line and transmitting a transmitted voice signal to the line, and a transmitted voice A side tone monitor for controlling the impedance of at least one side of the bridge circuit based on the level of the side tone signal monitored by inputting the signal and the received voice signal and monitoring the side tone signal level The impedance of at least one side of the bridge circuit based on the level of the monitored sidetone signal so that the sidetone signal is zero. Can be controlled by the monitor unit, it is possible to completely remove the sidetone signal has the operation and effect of the occurrence of howling can be completely prevented.

  According to a second aspect of the present invention, the side sound monitor controls the impedance of at least one side of the bridge circuit so that the level of the monitored side sound signal is equal to or less than a level at which no howling occurs. It has the action and effect that the occurrence of howling can be completely prevented.

  According to a third aspect of the present invention for solving the above problems, the side sound monitor is configured such that the impedance of one side of the bridge circuit is Z1, the impedance of the side facing one side is Z1A, and the impedance of the side adjacent to the one side is Z1A. The impedance of at least one side of the bridge circuit is controlled so that Z1 × Z1A = Z2 × Z2A, where Z2 is the impedance of the side facing the adjacent side and Z2A. Since it can be removed almost completely, it has the action and effect that the occurrence of howling can be surely prevented.

(Embodiment 1)
FIG. 1 is a block diagram showing a hands-free device according to Embodiment 1 of the present invention.

  In FIG. 1, a base unit 1, a line interface 2, a DSP 3, amplifiers 4 and 7, a speaker 5, a microphone 6, a reception line 9, a transmission line 10, a line echo canceller 31, a side tone signal subtractor 32, a transmission and reception attenuation factor Since the controller 33, the subtractors 34 and 35, the amplifiers 36 and 37, the acoustic echo canceller 38, and the echo signal subtractor 39 are the same as those shown in FIG. In addition, since the subunit | mobile_unit is not required for description of this invention, it is not illustrated. Reference numeral 40 denotes a sidetone monitor unit that inputs a transmission voice signal and a reception voice signal, monitors the sidetone signal level, and controls the impedance of at least one side of a bridge circuit to be described later based on the monitored sidetone signal level. It is.

  FIG. 2 is a circuit diagram showing a bridge circuit in the line interface 2 of FIG.

In FIG. 2, 9 is a reception line similar to FIG. 1, 10 is a transmission line similar to FIG.
Is a transistor for amplifying a transmission voice signal, 402 is a resistor having a resistance value Z1, 403 is an internal line of the base unit 1 having a telephone impedance Z (TEL), 404 is a line of line impedance Z (Line), and 405 is A resistor having a resistance value Z2, 406 is a resistor having a correction impedance Z (BN) together with an impedance of a capacitor 407 and a correction circuit 408, which will be described later, and 408 is connected in parallel to the resistor 406 to monitor a side tone. This is a correction circuit whose impedance (for example, capacitance) is controlled by a control signal a from the unit 40. By controlling the impedance of the correction circuit 408, the correction impedance Z (BN) is controlled.

  The operation of the bridge circuit of the hands-free device configured as described above will be described.

  The transmission voice signal from the transmission line 10 is amplified by the transistor 401 and transmitted to the line 404 having the line impedance Z (Line), and to the reception line 9 via the internal line 403 having the telephone impedance Z (TEL). Sent out. The transmission voice signal transmitted from the transmission line 10 to the reception line 9 is a side sound signal. The level of the side tone signal is affected by the balance of the bridge circuit of FIG.

  As described above, the impedance of the resistor 402 constituting one side of the bridge circuit is Z1, and Z1A = Z (TEL), where Z1A is the impedance of the line constituting the side facing the resistor 402 and the internal line. XZ (Line) / (Z (TEL) + Z (Line)). Further, the impedance of the resistor 405 adjacent to the resistor 402 is Z2, and the impedance constituting one side facing the resistor 405 is a corrected impedance Z (BN). As shown in FIG. 2, the correction impedance Z (BN) is an impedance obtained by adding the impedance of the capacitor 407 connected in series to the impedance when the resistor 406 and the correction circuit 408 are connected in parallel.

  At this time, if Z1 × Z1A = Z2 × Z (BN) is established, the above-described side tone signal is completely erased. Here, if Z (BN) = Z2A is substituted, the above equation becomes Z1 × Z1A = Z2 × Z2A. The side sound signal level increases as the values of Z1 × Z1A and Z2 × Z2A in the above equation differ.

  As described above, according to the present embodiment, the reception voice signal from the line is received by the reception line 9 via the line interface 2, and the transmission voice signal to the line is transmitted via the line interface 2. A bridge circuit in line interface 2 for receiving a received voice signal from a line and transmitting a transmitted voice signal to the line, and a transmitted voice By having the side sound monitor unit 40 that receives the signal and the received voice signal and monitors the level of the side sound signal and controls the impedance of at least one side of the bridge circuit based on the monitored side sound signal level, On the basis of the level of the monitored side tone signal, the side tone monitor unit 4 adjusts the impedance of at least one side of the bridge circuit so that the side tone signal becomes zero. Can be controlled, it is possible to completely remove the sidetone signal, the occurrence of howling can be completely prevented.

  Further, the sidetone monitor unit 40 can completely prevent the occurrence of howling by controlling the impedance of at least one side of the bridge circuit so that the level of the monitored sidetone signal is equal to or lower than the level at which no howling occurs. it can.

Further, the sidetone monitor unit 40 sets the impedance of one side of the bridge circuit to Z1, sets the impedance of the side facing one side to Z1A, sets the impedance of the side adjacent to one side to Z2, and sets the impedance of the side facing the adjacent side. By setting the impedance Z2A on at least one side of the bridge circuit so that Z1 × Z1A = Z2 × Z2A, the side sound signal can be almost completely removed, so that the occurrence of howling is ensured. Can be prevented.

  In the present invention, a reception voice signal from a line is received by a reception line via a line interface unit, and a transmission voice signal to the line is transmitted from the transmission line via a line interface unit, thereby enabling simultaneous bidirectional communication. Regarding the possible hands-free device, the side-tone signal can be completely removed, and the occurrence of howling can be completely prevented.

The block diagram which shows the hands-free apparatus by Embodiment 1 of this invention. A circuit diagram showing a bridge circuit in the line interface section of FIG. Block diagram showing a conventional hands-free device

Explanation of symbols

1 Base unit 2 Line interface 3 DSP
4, 7 Amplifier 5 Speaker 6 Microphone 9 Reception line 10 Transmission line 31 Line echo canceller 32 Side sound signal subtractor 38 Acoustic echo canceller 39 Echo signal subtractor 40 Side sound monitor unit 401 Transistors 402, 405, 406 Resistor 403 Inside Line 404 Line 407 Capacitor 408 Correction circuit

Claims (3)

Hands capable of simultaneous two-way communication by receiving a received voice signal from a line on a reception line via a line interface unit and transmitting a transmission voice signal to the line from the transmission line via the line interface unit A free device,
A bridge circuit in the line interface unit for receiving the received voice signal from the line and transmitting the transmitted voice signal to the line, and inputting the transmitted voice signal and the received voice signal to a side sound signal level. And a side-tone monitor that controls the impedance of at least one side of the bridge circuit based on the level of the side-tone signal monitored. 2. The handsfree device according to claim 1, wherein the sidetone monitor controls an impedance of at least one side of the bridge circuit so that a level of the monitored sidetone signal is equal to or lower than a level at which no howling occurs. apparatus. In the side sound monitor, the impedance of one side of the bridge circuit is Z1, the impedance of the side facing the one side is Z1A, the impedance of the side adjacent to the one side is Z2, and the side facing the adjacent side 3. The hands-free device according to claim 1, wherein the impedance of at least one side of the bridge circuit is controlled such that Z1 × Z1A = Z2 × Z2A, where Z2A is Z2.

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