JPH0543616U - Audio signal processor - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the residual sound when the electronic volume is set to the minimum volume. [Structure] The audio signal from the sound source 1 is an electronic VOL.
The volume is adjusted by the circuit 2. This volume is controlled by a volume control signal provided from the microcomputer 6 via the communication line 9. Pressing the DOWN switch 7 lowers the volume, and pressing the UP switch 8 increases the volume. The sound quality of the output from the electronic VOL circuit 2 is adjusted by the sound quality adjusting circuit 3. The sound quality adjustment is performed by a sound quality control signal provided through the communication line 10,
Adjust the high or low frequency gain. When the volume is at the minimum value, control is performed so that the low-frequency or high-frequency gain is minimized. The output from the sound quality adjustment circuit 3 is power-amplified by the AMP circuit 4 and sonicated by the speaker 5.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an audio signal processing device such as an audio reproducing device, and more particularly to a configuration for reducing residual noise.

[0002]

[Prior Art]

 Conventionally, in an audio reproducing apparatus, electric signals generated from a sound source such as a tape recorder, broadcasting, or a compact disc player are amplified in power and acoustically reproduced by a speaker or the like. Volume adjustment and sound quality adjustment are performed in the process of this signal processing. Volume adjustment adjusts the output level of the reproduced audio signal. The sound quality adjustment adjusts the sound quality that is reproduced by changing the frequency characteristic that amplifies the audio signal.

Volume adjustment generally attenuates the audio signal with a variable resistor. As the variable resistor, conventionally, one having a mechanical structure in which a movable electrode is slid on the surface of a strip-shaped resistor is used. In recent years, an electronic volume (sometimes abbreviated as “electronic VOL” hereinafter) combining a resistance network and an analog switch circuit has been integrated into a circuit and is now widely used. Using an electronic volume facilitates downsizing of the device and electronic control.

The tone control includes tone control and loudness as the sound quality adjustment. These tone adjustments are realized by the CR type with a buffer amplifier circuit or the NF type with a negative feedback loop of the amplifier circuit having frequency characteristics. To ensure a sufficient dynamic range of the amplifier circuit, sound quality adjustment is often performed on the output of the electronic volume.

[0005]

[Problems to be solved by the device]

 In the conventional audio reproducing apparatus for adjusting the sound quality of the output of the electronic volume, the volume adjustment of the electronic volume and the sound quality adjustment are controlled separately. For this reason, when the sound volume is minimized, if the high-frequency and low-frequency gains are increased by sound quality adjustment, the residual sound is amplified and sonicated, so noise is conspicuous and the reproduced sound becomes tactile. ..

An object of the present invention is to provide an audio signal processing device capable of reducing residual sound when volume adjustment is minimized.

[0007]

[Means for Solving the Problems]

 The present invention provides a control means for deriving a volume control signal for controlling the volume of an audio signal and a sound quality control signal for controlling the sound quality of the audio signal, and an output of an input audio signal in response to the volume control signal. The electronic volume whose volume is adjustable and the gain for the audio signal output from the electronic volume in response to the sound quality control signal are reduced in the high or low range compared to the middle range of the audio frequency band. Sound quality adjusting means capable of increasing in one adjustment band, and the control means stops the gain increase in the adjustment band in the sound quality adjusting means when the output volume represented by the volume control signal is the minimum value. The audio signal processing device is characterized by deriving various sound quality control signals.

The present invention also provides a control means for deriving a mute signal for cutting off the output of the audio signal and a sound quality control signal for controlling the sound quality of the audio signal, and a control means for responding to the mute signal to the input audio signal. A mute circuit that shuts off the output, and a gain for the audio signal output from the electronic volume that responds to the sound quality control signal, compared with the mid range of the audio frequency band. And a sound quality adjusting means capable of increasing the sound quality in the adjustment band, wherein the control means derives a sound quality control signal for stopping the increase in the profit in the adjustment band in the sound quality adjusting means when the mute signal is output. Is an audio signal processing device.

[0009]

[Action]

 According to the present invention, the audio signal processing device includes a control means, an electronic volume, and a sound quality adjusting means. The control means derives a volume control signal for controlling the volume of the audio signal and a sound quality control signal for controlling the sound quality of the audio signal. The electronic volume can adjust the output volume of the input audio signal in response to the volume control signal. The sound quality adjustment means can increase the gain for the audio signal output from the electronic volume in response to the volume control signal in at least one of the high frequency band and the low frequency band as compared with the middle frequency band of the audio frequency band. Is. The control means stops the gain increase in the adjustment band in the sound quality adjustment means when the output sound volume represented by the sound volume control signal has the minimum value. As a result, when the output volume of the audio signal is minimized, the residual sound is not amplified with the increased gain in the adjustment band of the sound quality adjustment means, and the residual sound that is acoustically reproduced can be reduced. It

Further, according to the present invention, since the gain increase is stopped at the time of outputting the mute signal, the residual sound can be reduced.

[0011]

【Example】

 FIG. 1 shows a schematic electrical configuration of an embodiment of the present invention. The volume of the audio signal from the sound source 1 is adjusted by the electronic VOL circuit 2, the sound quality is adjusted by the sound quality adjusting circuit 3, the power is amplified by the amplifying (hereinafter sometimes abbreviated as “AMP”) circuit 4, and the speaker is tuned. It is sonicated from 5. The electronic VOL circuit 2 and the sound quality adjustment circuit 3 are controlled by the microcomputer 6. The microcomputer 6 is provided with a DOWN switch 7 and an UP switch 8. In response to inputs from these switches 7 and 8, the microcomputer 6 controls the electronic VOL circuit 2 via the communication line 9. The volume control signal via the communication line 9 changes to decrease the volume when the DOWN switch 7 is pressed, and changes to increase the volume when the UP switch 8 is pressed. The sound quality control signal via the communication line 10 changes so that the gain of the adjustment band becomes the minimum when the volume adjustment value becomes the minimum value. The mute circuit 40 cuts off the audio signal when the transistor Tr is turned on in response to the mute signal from the microcomputer 6.

FIG. 2 shows an electrical configuration of the electronic VOL circuit 2 shown in FIG. A plurality of resistors 11, 12, 13, ... Are connected in series in the electronic VOL circuit 2, and an audio signal from the sound source 1 is given. As the sound source 1, a reproducing device such as a tape recorder, a broadcast receiving tuner, or a compact disc is used. One terminal of the switch circuit 20, 21, 22, ..., 2n is connected to each connection point of the resistors 11, 12, 13 ,. The switch circuits 20, 21, 22, ..., 2n are composed of analog switches, and the other terminals are commonly connected and connected to the input side of the sound quality adjustment circuit 3. The output from the latch circuit 30 is given to the control inputs of the switch circuits 20, 21, 22, ..., 2n. The latch circuit 30 stores a volume control signal given from the microcomputer 6 via the communication line 9 and controls ON / OFF of each switch circuit 20, 21, 22, ..., 2n.

For example, when only the switch circuit 20 is in the ON state and the other switch circuits 21, 22, ..., 2n are in the OFF state, the audio signal from the sound source 1 is not attenuated and the sound quality adjusting circuit is not attenuated. Given to 3. When only the switch circuit 21 is in the ON state, the audio signal from the sound source 1 is divided by the resistance 11 and the series resistance of the resistance 12 or less and given to the sound quality adjustment circuit 3. When only the switch circuit 2n is turned on, the audio signal from the sound source 1 is not given to the sound quality adjustment circuit 3 at all, and the sound volume is at the minimum level. In this way, the electronic VOL circuit 2 adjusts the volume of the audio signal from the sound source 1 according to the volume control signal given from the microcomputer 6 via the communication line 9.

FIG. 3 shows a configuration when tone control is performed by the sound quality adjustment circuit 3 shown in FIG. 1 and frequency characteristics thereof. FIG. 3 (1) shows a CR type tone control circuit. The audio signal from the electronic VOL circuit 2 is given to a high frequency (treble) control circuit TC and a low frequency (bus) control circuit BC including the electronic VOL circuit VR1. The high frequency control circuit TC is configured by connecting a capacitor C1, an electronic VOL circuit VR1 and a capacitor C2 in series. The low frequency control circuit BC is based on a series circuit of a resistor R1, an electronic VOL circuit VR2 and a resistor R2, and a capacitor C3 is connected between a connection point of the electronic VOL circuit VR2 with the resistor R1 and a movable terminal. Then, a capacitor C4 is connected between the movable terminal and the connection point between the other terminal of the electronic VOL circuit VR2 and the resistor R2.

The movable contacts of the electronic VOL circuits VR1 and VR2 are commonly connected and are given to the AMP circuit 4 shown in FIG. 1 via the buffer amplifier circuit BA. The buffer amplifier circuit BA amplifies an audio signal that is attenuated by inserting the high frequency control circuit TC and the low frequency control circuit BC. The frequency characteristic of the tone control circuit shown in FIG. 3 (1) is as shown in FIG. 3 (2). Compared with the frequency band around 1 kHz in the middle band, the response in the low band and the high band changes, and the overall frequency characteristic including the gain of the buffer amplifier BA changes. The sound quality adjustment circuit 3 shown in FIG. 1 is provided after the electronic VOL circuit 2 so that the buffer amplifier circuit BA is not saturated and a large dynamic range can be secured.

The CR tone control circuit shown in FIG. 3 (1) utilizes the fact that the impedances of the capacitors C1, C2, C3, and C4 are small in the high range and large in the low range, and thus the CR type tone control circuit shown in FIG. A characteristic change as shown is realized. That is, in the high range, the impedances of the capacitors C1 and C2 are smaller than the impedances of the resistors R1 and R2, and the change of the electronic VOL circuit VR1 greatly affects the response. The electronic VOL circuit VR2 is short-circuited by the capacitors C3 and C4, and its change hardly affects the response. In the high range, the impedances of the capacitors C1, C2, C3 and C4 become high, the change of the electronic VOL circuit VR1 has almost no influence on the response, and the change of the electronic VOL circuit VR2 determines the response.

The microcomputer 6 shown in FIG. 1 derives the sound quality control signal so that when the sound volume control signal minimizes the sound volume, the response in the high range and the low range by the tone control is also minimized. That is, the electronic VOL circuit VR1 of FIG. 3 (1) gives a sound quality control signal such that the movable contact moves to the capacitor C2 side and the movable contact of the electronic VOL circuit VR2 moves to the resistor R2 side. As a result, the high-frequency and low-frequency gain of the residual sound is reduced, and the residual sound that is sensational can be reduced.

Although tone control is performed by the sound quality adjustment circuit 3 in the above embodiment, it goes without saying that loudness control or the like may be performed. Loudness control is used to compensate for the fact that the frequency characteristics of human hearing depend on the sound pressure level, and that the sensitivity in the low range and high range becomes low when the sound pressure level is low. FIG. 4 illustrates changes in loudness characteristics according to another embodiment of the present invention. When the sound volume is at the minimum value, the frequency characteristics are flat, and when the sound volume is other than the minimum value, the relative gains in the low and high ranges are increased as the sound volume becomes smaller. In this way, it is possible to prevent the residual sound from feeling to the ear at the minimum volume.

In each of the above embodiments, tone control and loudness control are performed as the sound quality adjustment, but it goes without saying that the sound quality may be adjusted by a graphic equalizer or a parametric equalizer. Further, it goes without saying that these sound quality adjustments may be used in combination. Further, in a so-called mute state in which the output of the audio signal is cut off (a state in which the sound volume is greatly reduced), the gain increase in the adjustment band of the sound quality adjusting means is also stopped, that is, when the mute circuit 40 is operating in FIG. A configuration is also effective in which the gain of the adjustment band of the sound quality adjusting circuit 3 is minimized (when the transistor Tr is ON).

[0020]

[Effect of the device]

 As described above, according to the present invention, when the output volume from the electronic volume is minimized, the gain increase in the adjustment band of the sound quality adjusting means is also stopped, so that the residual sound reproduced as sound is reduced. be able to. As a result, when the audio signal to be acoustically reproduced is narrowed down to the minimum, it is possible to prevent only the residual sound from becoming a conspicuous reproduced sound and deteriorating the audible S / N ratio.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of an electronic VOL circuit 2 shown in FIG.

FIG. 3 is a block diagram showing an electrical configuration for performing tone control by the sound quality adjustment circuit 3 shown in FIG. 1 and a graph showing frequency characteristics thereof.

FIG. 4 is a graph showing frequency characteristics of loudness control according to another embodiment of the present invention.

[Explanation of symbols]

 1 sound source 2 electronic VOL circuit 3 sound quality adjusting circuit 4 AMP circuit 5 speaker 6 microcomputer 7 DOWN switch 8 UP switch 9, 10 communication line 40 mute circuit VR1, VR2 electronic VOL circuit BA buffer circuit TC high range control circuit BC low range control circuit

Claims (2)

[Scope of utility model registration request] 1. A control means for deriving a volume control signal for controlling the volume of an audio signal and a sound quality control signal for controlling the sound quality of an audio signal, and a control means for responsive to the volume control signal, the input audio signal An electronic volume whose output volume can be adjusted and a gain for an audio signal output from the electronic volume that responds to a sound quality control signal are adjusted in at least one of a high frequency band and a low frequency band in comparison with a mid frequency band of an audio frequency band. A sound quality adjusting means capable of increasing in a band, wherein the control means stops the gain increase in the adjusting band in the sound quality adjusting means when the output sound volume represented by the sound volume control signal has a minimum value. An audio signal processing device, wherein: 2. A control means for deriving a mute signal for cutting off the output of the audio signal and a sound quality control signal for controlling the sound quality of the audio signal, and for cutting off the output of the input audio signal in response to the mute signal. In response to the mute circuit and the sound quality control signal, the gain for the audio signal output from the electronic volume can be increased in at least one of the high frequency band and the low frequency band compared to the middle frequency band of the audio frequency band. An audio signal processing apparatus comprising: a certain sound quality adjusting means, wherein the control means derives a sound quality control signal for stopping the gain increase in the adjustment band in the sound quality adjusting means when the mute signal is output.