JP2655113B2 - Receiver volume limiting circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving sound volume limiting circuit, and more particularly to a receiving sound volume limiting circuit for limiting a gain of a receiving voice signal of a mobile telephone or the like.

[0002]

2. Description of the Related Art As shown in FIG. 5, a conventional telephone receiving sound volume limiting circuit includes a descrambling circuit 51 for decoding received voice signal data and a D / A section for converting the decoded data into an analog signal. 52, a volume control unit 53 that voltage-controls the analog signal level, a detection circuit 54 that generates a voice control voltage from the decoded received voice signal data, and an amplifier 55 (for example, see Japanese Patent Application Laid-Open JP-A-62-146032).

[0003] In particular, as a limitation on the receiving sound volume, a normal de-
In the case of scramble (scramble) operation, the volume control is not performed at all, and abnormal descrambling operation such as failure of the descrambling process or the difference of the scramble code between the transmission side and the reception side may result. In this case, the digital signal from the descramble circuit 51 is input to the detection circuit 54, and if an audio signal having a level equal to or higher than a predetermined value is frequently detected within a predetermined time, a high-level noise is output. When it is determined that the signal has occurred, the control circuit Vc is output from the detection circuit 54, and the volume control unit 53
Limits the receiving volume.

FIG. 6 is a block diagram of a multi-function telephone which detects a voltage of electric power supplied from an electronic exchange and limits the volume of a speaker when the voltage falls below a predetermined voltage. For example, Japanese Patent Application Laid-Open No.
No. 9, etc.). In particular, when the cable 62 is extended as a restriction on the receiving sound volume, a drop in the power supply voltage supplied from the electronic exchange 61 via the pulse transformer 63 is detected by the voltage detection circuit 65 and the power supply by the DC / DC converter 64 is detected. If it is determined that the supply will be hindered, the power consumption is limited by limiting the volume of the speaker amplifier circuit 67 with the volume limit signal 66, and the power supply voltage is prevented from lowering due to the extension of the cable 62, etc. Thus, a stable power supply from the DC / DC converter 64 is ensured.

[0005]

Therefore, in such a conventional receiving volume limiting circuit, the former aims to reduce the temporarily generated unpleasant sound, and the latter aims to secure the power supply voltage stably when the power supply drops. The purpose of the present invention is to mainly limit the receiving volume for the purpose of, and to effectively prevent the hearing impairment to the listener when the receiving volume is suddenly or continuously excessively input when listening to the normal receiving voice signal. It was difficult.

Further, in a conventional portable telephone, etc., the output sound pressure is passively set within a sound pressure level range where no hearing impairment occurs, based on the setting of the power supply voltage of the receiving amplifier and the electro-acoustic conversion efficiency of the receiver used. However, in practical use, the voice peak level often frequently exceeds the sound pressure level range due to the influence of ambient noise and the like, and according to the passive limiting circuit described above, However, since the receiving amplifier and the receiver electroacoustic characteristics near the upper limit level are in a non-linear region, there is a problem that the sound quality is significantly deteriorated. SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a receiving sound volume limiting circuit capable of preventing hearing loss to a listener at all times and obtaining a reproduced sound with less distortion.

[0007]

In order to achieve the above object, a receiving sound volume limiting circuit according to the present invention detects and rectifies an AC signal for driving a receiver and smoothes the signal, thereby obtaining a DC signal corresponding to the level of the AC signal for driving the receiver. a detection unit for outputting a signal, an a / D converter for converting a DC signal from the detection unit into a digital signal, by averaging the digital signal from the a / D converter for each predetermined time period Rights
Average and add and correct the stored current attenuation.
After calculating the time average value, the threshold value is compared with a predetermined threshold value indicating the critical sound pressure for listener's ear protection.If the time average value exceeds the threshold value, the excess level is calculated from the difference between the two, and the current level is calculated. While updating and storing as attenuation,
A control unit that outputs a volume attenuation instruction with the excess level as an attenuation amount, and a unit that attenuates the reception audio volume level by performing a subtraction process on the reception audio data, and responds to the volume attenuation instruction from the control unit. And a voice data calculation unit for performing a subtraction process on the received voice data based on the excess level included in the instruction and outputting the received voice data attenuated by the excess level.

The control unit compares the time average value with the threshold value, and when the time average value falls below the threshold value, determines whether or not the time average value is below the threshold value for a predetermined time. Monitoring is performed, and when the time average value falls below the threshold value for a predetermined period of time, a sound volume attenuation instruction for setting the attenuation amount to zero is output. Further, when the time average value falls below the threshold value for a predetermined period of time, the control unit issues a sound volume attenuation instruction to set a value that gradually changes from the current attenuation amount to zero within a predetermined time period. It is designed to output multiple times.

[0009]

Therefore, the AC signal for driving the receiver is converted into a DC signal by the detector, converted into a digital signal by the A / D converter and input to the controller, where it is averaged every predetermined time and averaged over time. When the value exceeds the threshold value, a volume attenuation instruction is output with the excess level as an attenuation amount. In response, the audio data calculation unit attenuates the received voice by the attenuation amount. The data is output, converted to a receiver driving AC signal, and output from the receiver.

[0010]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a receiving sound volume limiting circuit according to an embodiment of the present invention. In particular, a receiving circuit for converting and outputting digitally encoded receiving voice data into an analog signal is used in a receiving circuit of a mobile telephone. An example is shown. In FIG. 1, reference numeral 1 denotes a channel decoder which extracts control data and speech data 11 from a predetermined radio channel of a received radio signal and separates and outputs the speech data 11; A speech decoder (voice data calculation unit) that converts the PCM data into PCM data based on the voice compression method and attenuates and outputs the PCM data by subtracting the volume level of the PCM data in accordance with the volume attenuation instruction. Is a PCM decoder that converts the PCM data of this example into μLow data.

Reference numeral 4 denotes a D / A conversion unit for converting μLow data from the PCM decoder 3 into an analog signal, and reference numeral 5 denotes a D / A
A receiver amplifier that amplifies an analog signal from the conversion unit 4 and outputs a receiver driving AC signal 12 for driving the receiver 6. A receiver 7 detects and rectifies and smoothes the receiver driving AC signal 12 from the receiver amplifier 5 to convert a DC signal 13. An output detector 8 is an A / D converter for converting the DC signal 13 from the detector 7 into a digital signal, and 9 is an A / D converter 8.
A controller (controller) that compares the digital signal from the digital signal with a predetermined threshold value (threshold value) and outputs a sound volume attenuation instruction including the excess level 14 to the speech decoder 2 when the digital signal exceeds the threshold value. Part).

FIG. 2 is a functional block diagram showing the speech decoder 2. In FIG. 2, reference numeral 21 denotes a storage unit for storing audio sample data corresponding to each speech data 11,
Reference numeral 22 denotes a subtraction value register in which the excess level 14 is stored as a subtraction value in response to a volume attenuation instruction from the controller 9.
3 extracts audio sample data corresponding to the speech data 11 from the channel decoder 1 from the storage unit 21 and subtracts the volume of the audio sample data based on the subtraction value stored in the subtraction value register 22;
This is an arithmetic processing unit that outputs as M data.

FIG. 3 is a timing chart showing signals at various parts in FIG. 1. The operation of the present invention will be described below with reference to FIG. In FIG. 3, (a) shows speech data 11 output from the channel decoder 1, and the speech data 11 which is originally digital information is schematically shown as analog information. (B) Receiver amplifier 5
And (c) show a DC signal 13 outputted from the detector 7, and (d) shows an excess level 14 included in the volume attenuation instruction outputted from the controller 9.

Before time T0, speech data 11 of a predetermined volume level is output from channel decoder 1, converted into PCM data by speech decoder 2, and further transmitted via PCM decoder 3 and D / A converter 4. The signal is input to the receiver amplifier 5 and the receiver drive AC signal 12 is output to the receiver 6. At the same time, the receiver driving AC signal 12 is also input to the detection unit 7, where it is detected and rectified to become a DC signal 13, and the A / D conversion unit 8
After being converted into a digital signal by the controller 9
Is input to

FIG. 4 is a flowchart showing the processing procedure of the controller 9, and the operation of the controller 9 will be described below. In step 41, a digital signal indicating the level of the receiver driving AC signal 12 output to the receiver 6 is input from the A / D converter 8, and in step 42, the average is obtained at predetermined intervals to obtain a time average. The value is calculated, and in step 43,
The same amount of attenuation that is stored internally and that is currently set in the subtraction value register 22 of the speech decoder 2 is added to correct the time average value. Next, at step 44, the time average value and a predetermined threshold value VTH
Is compared with

The threshold value VTH is
Is set to a value corresponding to the critical sound pressure that can protect the listener's ear, for example, a value indicating 120 dBspl, and the calculated time average value is smaller than this threshold value VTH If there is no change and the time average value is “small → small”, it is determined that the audio level currently output from the receiver 6 is lower than the listener's ear protection critical sound pressure, and the process returns to step 41. Become. Accordingly, the controller 9 does not output the sound volume attenuation instruction, and outputs the receiver driving AC signal 12 having the same level as the level indicated by the speech data 11 from the channel decoder 1 to the receiver 6.

Thereafter, at time T0, when the level of the speech data 11 from the channel decoder 1 increases and the receiver drive AC signal 12 from the receiver amplifier 5 increases accordingly, this change is detected by the detector 7 and Detected by the controller 9 via the A / D converter 8, and in the aforementioned step 44, the receiver driving AC signal 12
If the time average value exceeds the threshold value and the time average value becomes “small → large”, the process proceeds to step 45, and the excess level, for example, 6 dB, is obtained from the difference between the two.
Is calculated and internally updated and stored as the current attenuation,
In step 46, a volume attenuation instruction including the excess level 14 is output from the controller 9 to the speech decoder 2.

In response, the excess level 14 included in the volume decay instruction is stored in the subtraction value register 22, and thereafter,
The arithmetic processing unit 23 of the speech decoder 2 subtracts the audio sample data read from the storage unit 21 corresponding to the speech data 11 from the channel decoder 1 by the excess level 14 stored in the subtraction value register 22. The processing is performed, and PCM data in which the sound level is attenuated by the excess level 14 minutes is output.

As described above, the means for subtracting the digitally encoded voice, that is, the PCM data, is provided in the speech decoder 2 so that the level of the receiver driving AC signal 12 output to the receiver 6 and the listener's ear protection are provided. Always compare with threshold value VTH corresponding to critical sound pressure,
When the level of the receiver drive AC signal 12 exceeds the threshold value VTH, a volume attenuation instruction including the excess level 14 is immediately output from the controller 9 to the speech decoder 2, and PCM data attenuated by the excess level 14 is output. Therefore, when a received voice that exceeds the critical sound pressure for protecting the listener's ear is input, the sound can be attenuated more quickly as compared with the conventional passive limiting circuit. At the same time, the sound can be attenuated with less distortion, so that it is possible to prevent a hearing disorder without a sense of discomfort to the listener.

If the level of the speech data 11 decreases at the time T1, the receiver driving AC signal 12 from the receiver amplifier 5 also decreases accordingly, and the DC signal 13 from the detector 7 also decreases. This is A /
The data is input to the controller 9 via the D conversion unit 8. Here, the controller 9 calculates the time average value in step 42 in the same manner as described above, adds and corrects the current attenuation amount stored therein in step 43, and then, in step 44, sets the threshold value VTH to Be compared.

As a result of the comparison, when the time average value falls below the threshold value VTH, that is, when the time average value becomes “large →
If the value has changed to "small", the process proceeds to step 47, where the time average value continues for the predetermined time td and the threshold value VTH
Is monitored, and if the time average value continuously falls below the threshold value VTH for the time td or more (step 47: YES), in step 48, the excess level 14 is set to zero and the current level is set to zero. After internally updating and storing the amount of attenuation, the process proceeds to step 46, where the controller 9 outputs to the speech decoder 2 a volume attenuation command with the excess level 14 being zero, that is, a volume attenuation cancellation command.

In response, the attenuation of the received voice in the speech decoder 2 is stopped, and the receiver driving AC signal 12 having the same level as the input received voice is output to the receiver 6. Thus, the predetermined time t
d When the time average continuously drops below the threshold value VTH, the attenuation for the received voice is stopped, so that even if the level of the received voice fluctuates to some extent, stable operation can be obtained. In addition, the insertion / release of the attenuation is not frequently performed according to the fluctuation, and it is possible to avoid a sense of discomfort to the listener.

In step 47, a predetermined time t
d If the time average has not continuously fallen below the threshold value VTH (step 47: NO), step 4
Returning to step 1, new voice data is input. Also, in step 44, the time average value is set to the threshold value V
If the time is still over TH, that is, if the time average value changes from “large to large”, the aforementioned steps 45 and 45 are performed.
Step 46 is executed, and a volume attenuation instruction corresponding to the excess level 14 is output.

In the above description, the predetermined time td
If the time average continuously falls below the threshold value VTH, steps 48 and 49 immediately execute the excess level 1
4 has been described for outputting a volume attenuation instruction of zero, the volume attenuation instruction may be output several times so that the excess level 14 gradually decreases from the immediately preceding value. By gradually reducing the amount of attenuation, the attenuation can be canceled more naturally.

[0025]

As described above, according to the present invention, the audio data calculation unit having means for attenuating the reception sound volume level by performing the subtraction process on the reception sound data is provided, and the control unit controls the receiver. The time average value indicating the average value of the driving AC signal is compared with a predetermined threshold value indicating the critical sound pressure for protecting the listener's ear, and when the time average value exceeds the threshold value, the excess level is calculated from the difference between the two. By outputting a sound volume attenuation instruction using the excess level as the attenuation amount to the audio data calculation unit, the audio data calculation unit outputs the received voice data attenuated by the excess level, so that the listener's ear protection is provided. When a received voice that exceeds the critical sound pressure is input, it can be attenuated more quickly than a conventional passive limiting circuit, And it becomes possible to provide a small attenuation distortion, it is possible to carry out prevention of discomfort without hearing for the listener.

Further, the control unit compares the time average value with the threshold value, and when the time average value falls below the threshold value, determines whether or not the time average value falls below the threshold value for a predetermined time. If the time average value falls below the threshold value for a predetermined period of time, the volume attenuation instruction is set so that the attenuation amount is set to zero, so that even when the received voice level fluctuates to some extent, Thus, a stable operation can be obtained, and the insertion / release of the attenuation is not frequently performed in accordance with the fluctuation, thereby making it possible to avoid a sense of discomfort to the listener. Further, when the time average value falls below the threshold value for a predetermined period of time, the control unit issues a sound volume attenuation instruction to set a value that gradually changes from the current attenuation amount to zero within a predetermined time period. Since it is output multiple times, the amount of attenuation can be reduced more smoothly,
It is possible to cancel the attenuation more naturally.

[Brief description of the drawings]

FIG. 1 is a block diagram of a receiving sound volume limiting circuit according to an embodiment of the present invention.

FIG. 2 is a functional block diagram showing speech data.

FIG. 3 is a signal waveform diagram in each section of the embodiment shown in FIG.

FIG. 4 is a flowchart showing a processing procedure of a controller.

FIG. 5 is a block diagram of a conventional reception volume limiting circuit.

FIG. 6 is a block diagram of another conventional receiving sound volume limiting circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Channel decoder, 2 ... Speech decoder (sound data operation part), 3 ... PCM decoder, 4 ... D / A conversion part, 5 ... Receiver amplifier, 6 ... Receiver, 7 ... Detection part,
8 A / D converter, 9 Controller (control unit), 11
... Speech data, 12 ... Receiver driving AC signal, 13
... DC signal, 14 ... Excess level.

Claims (3)

(57) [Claims] 1. A receiver circuit for converting digitally encoded received voice data into an analog receiver driving AC signal and outputting the converted signal from a receiver, wherein the receiver driving AC signal is detected and rectified and smoothed.
A detector for outputting a DC signal corresponding to the level of the receiver driving AC signal, an A / D converter for converting the DC signal from the detector into a digital signal, and a digital signal from the A / D converter. A time average was calculated by averaging every predetermined time, and the stored current attenuation was added and corrected to obtain a time average value.
Thereafter , the threshold value is compared with a predetermined threshold value indicating the critical sound pressure for protecting the listener's ear, and when the time average value exceeds the threshold value, an excess level is calculated from the difference between the two and updated and stored as the current attenuation value. And a control unit that outputs a sound volume attenuation instruction using the excess level as the amount of attenuation, and a unit that attenuates the received sound volume level by performing a subtraction process on the received sound volume data. A voice data calculation unit that performs a subtraction process on the received sound volume data based on the excess level included in the command in response to the volume attenuation command, and outputs the received sound volume data attenuated by the excess level. A receiving volume limiting circuit. 2. The reception volume limiting circuit according to claim 1, wherein the control unit compares the time average value with the threshold value, and when the time average value falls below the threshold value, a predetermined time period. It continuously monitors whether the time average value falls below the threshold value, and if the time average value falls below the threshold value continuously for the predetermined time, a volume attenuation instruction to set the attenuation amount to zero. A receiving sound volume limiting circuit characterized in that a receiving sound volume limiting circuit is output. 3. The reception volume limiting circuit according to claim 2, wherein the control unit is configured to, when the time average value falls below the threshold value continuously for the predetermined time, reduce the current attenuation amount within a predetermined period. A receiving volume control circuit for outputting a volume attenuation command a plurality of times, wherein the volume attenuation command has a value that gradually changes from zero to zero.