JPH05264332A - Detecting device for extraneous sound and audio output device - Google Patents

Abstract

PURPOSE:To obtain a detecting device of an extraneous sound and an audio output device which makes it possible to detect the extraneous sound in distinction from an audio signal and to execute an automatic control for increasing and decreasing an audio output of an acoustic apparatus in accordance with the kind of the extraneous sound, in the acoustic apparatus or the like. CONSTITUTION:An impedance 3 for detecting a current is connected in series to a speaker coil 2c and a voltage generated at the opposite ends of the impedance 3 for detecting the current in this series circuit is taken out. A difference between this voltage taken out and a signal voltage impressed on a speaker 2 is determined by a differential amplifier 5 and a counterelectromotive force so generated in the speaker 2 as to correspond to an extraneous sound is detected therefrom.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided with an audio device such as an audio device and is capable of detecting an external sound such as noise coming into a speaker, and a sound corresponding to the external sound. The present invention relates to an audio output device whose output is controlled.

[0002]

2. Description of the Related Art In the case of audio equipment, for example, audio equipment, it is not preferable to hear an external sound such as noise at the same time as an amplified audio signal. When the external sound is noise, it is necessary to change the audio output from the speaker according to the level of the external sound. On the other hand, when the foreign sound is a ringing sound of the telephone, it is necessary to lower the voice output.

Conventionally, an apparatus for picking up and detecting an external sound with a microphone, for example, is used in distinction from an audio output circuit including a speaker. In addition, measures are being taken such as installing audio equipment in a soundproof room so that external noise is not mixed.

[0004]

In the conventional detection device,
Since it is not possible to pick up only external sound with the microphone and also the sound from the speaker at the same time, it is difficult to distinguish only external sound. It has a complicated structure such as having to take measures. In addition, depending on the type of external sound, it is necessary to raise or lower the original audio output, but there is not yet provided one that can control the audio output simply by detecting the external sound.

An object of the present invention is to add a circuit having a simple structure in an audio device so that only an external sound can be detected, and the audio output of the audio device is automatically controlled according to the type of the external sound. In other words, it is possible to provide an external sound detection device and a voice output device that can perform the operation.

[0006]

SUMMARY OF THE INVENTION According to the present invention, an external sound is obtained from a current detection impedance connected in series with a speaker coil and a difference between a voltage generated across the current detection impedance and a signal voltage applied to the speaker. And a differential amplifying means for detecting a back electromotive force generated in the speaker corresponding to the above.

Further, according to the present invention, a speaker corresponding to an external sound is obtained from an impedance for current detection connected in series with the speaker coil and a difference between a voltage generated across the impedance for current detection and a signal voltage applied to the speaker. And a voice signal to be applied to the speaker when a ringing tone is detected by detecting only the ringing tone of the telephone among the signals output by the differential amplifying unit. And a de-voicing means for muting the voice output device.

According to the present invention, a speaker corresponding to an external sound is obtained from a current detection impedance connected in series with the speaker coil, and a difference between a voltage generated across the current detection impedance and a signal voltage applied to the speaker. A differential amplifier for detecting the back electromotive force generated in the, and the signals output by the differential amplifier are averaged, and when the level of the averaged signal is high, the level of the audio signal applied to the speaker is increased, An audio output device comprising: a level adjusting unit for lowering the level when the level is low.

[0009]

According to the present invention, the current is flowing in the series circuit of the speaker coil and the current detecting impedance corresponds to the voltage difference between the voice signal voltage and the counter electromotive force generated in the speaker by picking up an external sound. It is the value. A voltage corresponding to the current is is generated in the current detection impedance in the series circuit. By obtaining the difference between this voltage and the signal voltage applied to the speaker by the differential amplifying means, an output proportional to the external sound can be obtained and the external sound can be detected.

Further, according to the present invention, it is possible to mute the voice signal applied to the speaker by detecting only the ringing tone of the telephone from the signals output by the differential amplifying means by the devoicing means. Therefore, the inconvenience that the external sound is the ringing sound of the telephone and should be answered, but the ringing sound cannot be heard due to the sound from the audio device and cannot be dealt with is solved.

Further, according to the present invention, the level of the audio signal applied to the speaker can be controlled by the level adjusting means provided with the output of the differential amplifying means. Therefore, it is possible to listen to music or the like under a comfortable situation by increasing the volume when the external sound is loud and noisy, and conversely by lowering the volume when the volume is small and quiet.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an electric circuit diagram showing a main part of a first embodiment of the present invention. The audio input terminal I provided on the audio equipment is
An audio signal V (voltage) is given, and this audio signal V is input to the speaker drive amplifier 1. This amplifier 1 amplifies a voice signal V with an amplification factor A and outputs it as an output A × V to a speaker 2
To the coil 2C. A current detection impedance 3 is connected in series to the speaker coil 2C.

On the other hand, the audio input terminal I is connected to the input end of a gain adjusting circuit 4 which is a gain adjusting means. The gain adjusting circuit 4 is composed of an amplifier having a predetermined gain (transfer function) described later. The output of this gain control circuit 4,
The divided voltage generated at the series connection point B in the series circuit of the speaker coil 2C and the current detection impedance 3, that is, the divided voltage of the impedance 3 is input as a comparison signal to the differential amplifier 5 which is the differential amplification means. ..
The differential amplifier 5 transmits the output e ₀ proportional to the difference between the two types of input signals to the output terminal O.

When the impedance of the coil 2C of the speaker 2 is Z and the impedance of the current detecting impedance 3 is R, the current is ₁ flowing through the speaker 2 due to the output A × V of the speaker drive amplifier ₁ is

[0015]

## EQU1 ## is ₁ = (A × V) / (R + Z) Actually, an external sound, for example, noise N is induced to the speaker 2. Therefore, if the counter electromotive force generated in the speaker 2 by the external noise N is e _N , the current is actually flowing in the speaker 2. Is

[0016]

[Number 2] is = a (A × V) / (R + Z) -e N / (R + Z). Based on this current, the divided voltage e _s generated at the series connection point B is

[0017]

[Equation 3] e _s = R · is.

The gain (transfer function) of the gain adjusting circuit 4 realized by the phase / gain adjuster is set to a predetermined value A · R / (R +
Z), that is, when preset to a value corresponding to the voltage division ratio of the current detection impedance 3 in the series circuit,
The output signal e _T of the gain adjusting means 4 at the output terminal C is

[0019]

[Equation 4] e _T = V × A · R / (R + Z) When the difference between the two types of signals expressed by the _equations 3 and 4 is obtained by the differential amplifier 5, the signal e ₀ at the output terminal O is

[0020]

[Equation 5] e ₀ = e _T −e _S , e ₀ = (A × R × V) / (R + Z) − (A × V) / (R + Z) + (R × e _N ) / (R + Z) e ₀ = (R × e _N ) / (R + Z)

Therefore, the signal e ₀ is a signal proportional to only the external noise, and it is possible to detect the external noise.

FIG. 2 is an electric circuit showing a main part of a second embodiment of the present invention. The foreign sound detection circuit unit 10 is equivalent to the circuit shown in FIG. The output of the external sound detection circuit unit 10 is
It is added to a de-voicing circuit 15 including a detector 11, a comparator 12, a cut / reset circuit 13, and a muting transistor 14. The external noise proportional output e ₀ output from the differential amplifier 5 is input to the detector 11. The detector 11 has a function of detecting and detecting only a ringing tone of a commercially available telephone, for example, a signal indicating a bell tone. The ringing tone signal detected by the detector 11 is given to the comparator 12,
When a ringing tone signal of a predetermined level or higher is input, the comparator 12 produces an output "H". Comparator 1
The output "H" of 2 is input to the set terminal of the set / reset circuit 13 in the next stage.

The set / reset circuit 13 is formed by an RS flip-flop circuit and has a set terminal S.
When a logical output "H" is input to the reset terminal R, the output terminal outputs a DC voltage of a predetermined value indicating a high level, and the reset terminal R
Since the reset signal is input to the set terminal S and the logical output “H” is not input to the set terminal S, the output terminal operates to hold the zero potential indicating the low level. In this case, the reset signal input to the reset terminal R is
A reset signal is given from a telephone and is interlocked with the fact that the reset switch 16 of the telephone is switched from on to off when the call ends.

The DC voltage output from the set / reset circuit 13 is applied as a base potential to the muting transistor 14 provided on the audio equipment side. The muting transistor 14 conducts when a DC voltage is applied to the base, and grounds the input signal from the audio input terminal I to the speaker drive amplifier 1. As a result, it is possible to weaken the acoustic signal of an audio device such as an audio device. As described above, in the embodiment shown in FIG. 2, when the bell of the telephone rings, the acoustic signal is automatically reduced to make the consumer recognize that the telephone is ringing and to prevent the call. Try not to be. After the telephone conversation is completed, the reset switch 16 can restore the original state before the telephone rings.

FIG. 3 is an electric circuit diagram showing a main part of a third embodiment of the present invention. The external sound detection circuit unit 10 is formed in a circuit equivalent to the circuit shown in FIG. The output of the external sound detection circuit section 10 is added to a level adjustment circuit 24 including a detector 21, a signal averaging circuit 22, and an audio signal adjustment circuit 23. External noise proportional output e ₀ output from the differential amplifier 5
Is input to the detector 21. The detector 21 is formed by a level discrimination circuit that discriminates whether or not there is an input of a predetermined level or higher.

The signal detected by the detector 21 and having a predetermined noise amount or more is supplied to the signal averaging circuit 22 in the next stage. The signal averaging circuit 22 is formed by, for example, an integrating circuit,
It has the function of calculating the average value of the signals that fluctuate within the set time. The signal averaged by the signal averaging circuit 22 is given as a control signal to the audio signal adjusting circuit 23 implemented by an electronic volume provided in the circuit of the audio device.

The electronic volume 23 is turned up in an environment where the noise level is high such as daytime according to the level of the input control signal, and is turned down in an environment where the noise level is early such as early morning and late at night. It is possible to automatically set a comfortable volume by responding only to the surrounding conditions without responding to the voice generated by.

[0028]

As described above, according to the present invention, it is possible to reliably detect the external sound signal mixed with the audio signal and entering the speaker by the differential amplifier.
Since the external sound volume can be recognized not only as a sensory but also as accurate data, it is possible to rationally and scientifically take measures against noise low frequencies.

Further, of the external sounds, for the telephone ringing sound or the like which is rather necessary for maintaining the life, the voice generated by the speaker can be automatically muted by the function of the de-voicing means. Inconveniences such as forgetting to pick up the phone are eliminated.

Further, the volume of the audio device can be automatically adjusted to high or low by the level adjusting means depending on whether the surrounding environment is noisy or quiet, which is excellent in that the comfortable volume according to the environment can be maintained. The effect is played.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a main part of a first embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing a main part of a second embodiment of the present invention.

FIG. 3 is an electric circuit diagram showing a main part of a third embodiment of the present invention.

[Explanation of symbols]

 2 speaker 2C speaker coil 3 current detection impedance 4 gain adjustment circuit 5 differential amplifier 11 wave detector 15 unvoiced circuit 22 signal averaging circuit 23 audio signal adjustment circuit 24 level adjustment circuit

Claims (3)

[Claims] 1. A speaker corresponding to an external sound is generated from an impedance for current detection connected in series with a speaker coil and a difference between a voltage generated across the impedance for current detection and a signal voltage applied to the speaker. An external sound detection device comprising: a differential amplification means for detecting a back electromotive force. 2. An external sound is generated in the speaker from the difference between the current detection impedance connected in series with the speaker coil and the voltage generated across the current detection impedance and the signal voltage applied to the speaker. A differential amplifying means for detecting a back electromotive force and only a ringing tone of a telephone is detected from the signals output by the differential amplifying means, and when the ringing tone is detected, a voice signal applied to a speaker is muted. A voice output device, comprising: 3. An external sound is generated in the speaker from the difference between the current detection impedance connected in series to the speaker coil and the voltage generated across the current detection impedance and the signal voltage applied to the speaker. A differential amplifier that detects a back electromotive force and a signal output by this differential amplifier are averaged. When the level of the averaged signal is high, the level of the audio signal applied to the speaker is raised, and when it is low, the level is increased. An audio output device comprising: a level adjusting unit for lowering the level.