JPH03145811A - Audio output level controller - Google Patents

Abstract

PURPOSE:To give no sense of displeasure to a 3rd party in the vicinity by adjusting a gain of a gain variable amplifier circuit with a noise measuring voltage when the noise measuring voltage is higher than a 2nd threshold level, and adjusting the gain with the gain control voltage when the noise measuring voltage is smaller. CONSTITUTION:When a surrounding noise level is comparatively high and a noise measuring voltage from a noise level measuring means 1 exceeds a threshold level A, a control method changeover circuit 7 allows a switch 5 to select terminal (a). The noise measuring voltage from the noise level measuring means 1 is applied to a gain variable amplifier circuit 2 via the switch 5. Thus, the S/N is always made constant. When the surrounding noise level is small and the noise measuring voltage from the noise level measuring means 1 is smaller than the threshold level A, the control method changeover circuit 7 allows a switch 5 to select terminal (b) and the gain control voltage from the gain control means 6 is applied to the gain variable amplifier circuit 2 as the control voltage.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention relates to an audio output level control device, and in particular, the present invention relates to an audio output level control device, and in particular, even when the noise level is extremely low such as late at night, loud &ffl. The present invention relates to an audio output level control device that does not generate output.

(Prior Art) Recently, audio devices have been developed in which the audio output level can be adjusted according to the surrounding environment, and these devices are used in car stereos and the like. When listening to music through a car stereo, the noise generated by the car may make it difficult to hear the output audio. The noise generated by automobiles is relatively loud and its level fluctuates widely and rapidly. Therefore, in order to enjoy music comfortably, it is necessary to frequently adjust the volume of the car stereo so that the volume is sufficient and not too loud. The volume is automatically adjusted based on the surrounding noise level.

FIG. 5 is a block diagram showing such a conventional audio output level control device.

The noise level measuring means 1 measures the ambient noise level by, for example, detecting the rotation speed of an automobile engine, and outputs a control voltage to the variable gain amplifier circuit 2. The gain of the variable gain 1q amplifier circuit 2 is changed by this control voltage. The audio signal from the signal source 3 is applied to the variable gain amplifier circuit 2, amplified with a gain based on the control l voltage, and applied to the speaker 4.

FIG. 6 is a graph showing the characteristics of the variable gain amplifier circuit 2, with the horizontal axis representing the noise level and the vertical axis representing the gain of the variable gain amplifier circuit 2. As shown in FIG. 6, as the surrounding noise level increases, the gain 1q also increases.

In this way, the speaker is provided with an audio output whose level increases in accordance with the surrounding noise level, and a constant S/N ratio is always ensured.

By the way, when the background noise level is extremely low, such as indoors late at night, the control voltage level from the noise level measuring means 1 is approximately constant and does not follow minute changes in the noise level. Therefore, when the device shown in FIG. 5 is used indoors late at night, the gain of the variable gain amplifier circuit 2 does not change, and the audio signal from the signal source 3 is amplified with a relatively high gain, and the third Sometimes the sound level becomes too high, which I feel uncomfortable.

Similarly, even if the device shown in FIG. 5 is applied to a television receiver, gain adjustment is not performed at late night, etc., because the background noise level is extremely low. In television broadcasting, the difference in the high-pitched voice level between commercials and broadcast programs can be relatively large, so if you watch with the volume fixed, a relatively high-level audio signal will be output, which may cause discomfort to third parties. Sometimes I feel that way.

(Problems to be Solved by the Invention) As described above, the conventional audio output level control device 611 described above is effective when the ambient noise level is relatively high, such as during the daytime, but When the background noise level is extremely low, as in the case of the background noise level, there is a problem in that the audio output level is so high that it may cause discomfort to a third party.

The present invention has been made in view of such problems, and includes:
When the background noise level is high, an audio signal of a sufficient level can be output, and when the background noise level is low, the audio signal level can be adjusted so as not to cause discomfort to third parties in the vicinity. The aim is to provide an audio output level control device that can cover over.

[Structure of the Invention] (Means for Solving the Problems) In the audio output level control device according to the present invention, the noise level measuring means outputs a noise measurement voltage based on the 1Jf5 level, and the input signal level measuring means outputs a noise measurement voltage based on the 1Jf5 level. The gain control means outputs a gain control voltage at a constant level until the noise measurement voltage exceeds a first threshold value, and when the noise measurement voltage exceeds the first threshold value, the gain control means outputs an input measurement voltage based on the input signal level. A gain control m voltage whose level decreases as the voltage rises is output, and the control method switching means changes the gain of the variable gain amplifier circuit that amplifies the input signal to the noise measurement voltage when the noise measurement voltage is higher than the second threshold. It is adjusted by the voltage, and when the noise measurement voltage is smaller than the second threshold value, the rIA is adjusted by the gain control tllll voltage.

(Function) In the present invention, when the noise level is higher than the second threshold, the S/N ratio of the output audio signal is kept constant by adjusting the gain of the variable gain amplifier circuit based on the noise measurement voltage. I have to. When the noise level is lower than the second equivalent value, the i, IJ m method switching means adjusts the gain of the variable gain amplifier circuit by the gain control voltage from the gain control means. The gain control voltage is approximately constant when the noise level is lower than the first threshold, and decreases as the input measurement voltage increases when the noise level is higher than the first threshold. In other words, when the noise level is low, the output audio level is limited as the input signal level increases.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a block diagram showing an embodiment of a B output level control device according to the present invention.

In FIG. 1, the same components as in FIG. 5 are given the same reference numerals.

The noise level measuring means 1 receives ambient noise as input and converts this noise into r? After electrical conversion, the detection rectification is performed, and a noise measurement voltage corresponding to the noise level is output to the terminal a of the switch 5, and the control means 6 and the control method switching circuit 7
Also output to. The terminal of the switch 5 is the gain control voltage from the gain control means 6! The common terminal C is connected to the control input terminal of the variable gain amplifier circuit 2. The variable gain amplifier circuit 2 amplifies the audio signal from the signal source 3 with a gain proportional to the control voltage applied to the control input terminal, and supplies the amplified signal to the speaker 4 for audio output.

The control method switching circuit 7 controls the switch 5 based on the noise measurement voltage, and the noise measurement voltage is set to a predetermined threshold value A.
If it is higher than , switch 5 connects terminal a4! : selected, and if it is lower than the threshold value A, the switch 5 is made to select the terminal. Note that the threshold value A is set to the level of the noise measurement voltage output from the noise level measurement means 1 when relatively large noise is input.

On the other hand, the audio signal from the signal source 3 is input to the input signal level measuring means 8 . The input signal level measuring means 8 detects and rectifies this input audio signal and outputs an input measurement voltage corresponding to the input audio signal level. The gain control means 6 outputs a gain control voltage based on the input measurement voltage and the noise measurement voltage. That is, the gain control circuit 6 outputs a gain control voltage at a constant level regardless of the input measurement voltage until the noise measurement voltage from the noise level measurement means 1 reaches the predetermined threshold B. When it exceeds the voltage, a gain control 11 voltage whose level decreases as the input measurement voltage increases is output. Note that the threshold value B is set to the level of the noise measurement voltage when relatively small noise is input.

Next, the operation of the audio output level control ill device configured as described above will be explained with reference to FIGS. 2 to 4. FIG. 2 is a graph showing the change in gain when the noise level is high and the noise measurement voltage is higher than the threshold 11fiA, with the horizontal axis representing the noise level and the vertical axis representing the gain of the variable amplifier circuit 2. FIG. 3 is a graph showing the characteristics of the gain control means 6 with the horizontal axis representing the input measurement voltage and the vertical axis representing the gain control voltage, and FIG. 4 showing the noise level on the horizontal axis and the audio output level on the vertical axis. This is a graph showing the output characteristics measured by increasing the input signal linearly when the noise level is low and the noise measurement voltage is lower than the threshold value A.

It is now assumed that the ambient noise level is relatively high and the noise measurement voltage from the noise level measuring means 1 exceeds the threshold value Δ. Then, the control method switching circuit 7 causes the switch 5 to select the terminal a. As a result, the noise measurement voltage from the noise level measuring means 1 is applied as a control voltage to the variable gain amplifier circuit 2 via the switch 5, and as shown in FIG. Increases as the temperature rises. The audio signal amplified by the variable gain amplifier circuit 2 is given to a speaker 4 and output as audio. In this case, the audio output level increases as the noise level increases, so that the S/N ratio remains constant.

On the other hand, when the ambient noise level is low and the noise measurement voltage from the noise level measuring means 1 is smaller than the threshold value A, the control method switching circuit 7 causes the switch 5 to select the terminal. Thereby, the gain control voltage from the gain control means 6 is applied to the variable gain amplifier circuit 2 as a control voltage.

The gain control voltage of the gain control means 6 changes depending on the level of the noise measurement voltage, as shown in FIG. The discontinuity point in the voltage of the gain control circuit 11 in FIG. 3 indicates the point in time when the noise measurement voltage exceeds the threshold value B. When the ambient noise level is low, the gain control circuit has the characteristics shown on the left side of the paper. As the noise level increases, the characteristics shift to the right side of the paper. As shown in Figure 3, the noise measurement voltage is at threshold B
, the gain control means becomes smaller as the input signal level becomes larger. On the other hand, when the noise measurement voltage is smaller than the threshold value B, a constant gain measurement voltage is always output regardless of the input signal level.

The gain 1q of the gain 1q variable amplifier circuit 2 is controlled by this gain 111 control voltage. As shown in FIG. 4, until the noise level is low and the noise measurement voltage reaches the threshold value B, the gain of the variable gain amplifier circuit 2 is constant, and an n-type output is produced at a level proportional to the audio input signal level. Ru. When the noise level becomes slightly higher and the control pressure reaches the threshold (+flfB), the gain control voltage decreases as shown in FIG. 3, and the gain of the variable gain amplifier circuit 2 is suppressed. As shown in FIG. 4, the upper limit of the audio output level is limited regardless of the increase in the audio signal level from the signal source 3.

In this way, in this embodiment, the gain of the input signal is switched based on the noise level, and when the noise level is relatively high, the S/N is improved by amplifying with a gain proportional to the change in the noise level. When the ratio is held constant and the noise level is relatively low, the gain of the input signal is limited to limit the upper limit of the audio output level. In addition, the gain control voltage has different characteristics depending on the magnitude of the noise level, that is, whether the audio output leaks or is small to the surroundings.
Even when the noise level is extremely low, such as late at night, the & production output is prevented from producing unpleasant sound R.

[Effects of the Invention] As explained above, according to the present invention, sufficient sound is maintained against surrounding noise, and the audio output level during low noise is limited, so that third parties in the vicinity This has the effect of not causing discomfort to the patient.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of an audio output level control device according to the present invention, FIGS. 2 to 4 are graphs for explaining the embodiment, and FIG. 5 is a conventional audio output level control device. FIG. 6 is a graph for explaining a conventional example. DESCRIPTION OF SYMBOLS 1... Noise level measuring means, 2... Variable gain amplifier circuit, 3... Signal source, 5...
Switch, 6... Gain control means, 7... Control method switching circuit, 8... Input signal level measuring means. Fig. 2 N force measurement peeking pressure Fig. 4 Fig. 5 Fig. 6

Claims (1)

[Scope of Claims] Noise level measuring means for measuring a noise level and outputting a noise measurement voltage based on the noise level; and input signal level measuring means for measuring an input signal level and outputting an input measurement voltage based on the input signal level. , gain control means that outputs a gain control voltage at a constant level until the noise measurement voltage exceeds a first threshold, and outputs a gain control voltage that decreases as the input measurement voltage increases when the noise measurement voltage exceeds the first threshold; and a variable gain amplifier circuit that amplifies and outputs the input signal with a gain based on the noise measurement voltage or the gain control voltage, until the noise measurement voltage exceeds a second threshold higher than the first threshold. An audio system characterized by comprising control method switching means for applying the gain control voltage to the variable gain amplifier circuit, and applying the noise measurement voltage to the variable gain amplifier circuit when the noise measurement voltage exceeds a second threshold. Output level control device.