JP2000341787A - Acoustic device and hearing aid using the same device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acoustic device capable of inexpensively and securely preventing the generation of a howling sound while holding a simple constitution and a hearing aid using the acoustic device. SOLUTION: The acoustic device provided with at least a sound input means 11 such as a microphone for converting a sound into an electric signal, a signal amplification means 12 for amplifying an input signal Si inputted from the means 11 and a sound output means 15 such as a speaker for outputting a sound in response to an output signal So from the means 12 has, between the means 12 and 15, a phase switching means 14 for shifting the phase of the output signal So relative to the input signal Si and the means 14 is driven so as to shift the phase of the output signal So relative to the input signal Si when the signal level of the input signal Si reaches a prescribed level.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio device such as a karaoke device and an audio device used for a loudspeaker such as a loudspeaker and a hearing aid, and more particularly to a circuit configuration thereof.

2. Description of the Related Art Conventionally, when a sound input from a microphone or the like is amplified and output from a speaker or the like, the sound from the speaker is fed back to the microphone and amplified again, so that the sound is referred to as “Pee”. A phenomenon called a howling phenomenon that generates an extremely loud abnormal noise (hereinafter referred to as a “howling sound”) is well known. In particular, hearing aids of the type used for insertion into the ear have a very short distance between the speaker and the microphone in terms of shape, and the sound from the speaker is returned to the microphone via the gap between the ear and the skeleton. It was difficult to stably prevent the howling phenomenon. When a howling sound is generated nearby, the loud sound not only makes it difficult to hear a normal sound, but also makes it impossible to hear a warning sound or the like indicating a danger.
In particular, when a howling phenomenon occurs in the hearing aid, not only during the time when the howling sound is occurring, howling sound is generated by pressing the hearing aid but eliminating the gap with the ear, removing the hearing aid, or turning off the power For a while after stopping, the sound may not be heard properly due to the paralysis of the auditory nerve, and a dangerous state may continue for a long time. In order to prevent this howling phenomenon, Japanese Patent Application Laid-Open No.
In 2397, howling and its frequency are detected,
There is disclosed a technique for preventing the occurrence of howling by phase-shifting and adding frequencies according to the detected frequency.

However, in the above-described method, a howling detection circuit for detecting a howling frequency is required. However, it is difficult to exactly detect howling sound, and the configuration of the detection circuit is complicated. Therefore, there is a problem that it is difficult to further reduce the size or the cost of a small acoustic device such as a hearing aid. Therefore, the present invention has a simple configuration,
It is an object of the present invention to provide an audio apparatus capable of reliably preventing howling sound from being generated at a lower cost and a hearing aid using the same.

Means for Solving the Problems In order to solve the above-mentioned problems, an acoustic device according to claim 1 includes a sound input means (11) such as a microphone for converting sound into an electric signal, and a sound input means (11). At least a signal amplifying means (12) for amplifying an input signal (Si) and a sound output means (15) such as a speaker for outputting a sound in response to an output signal (So) from the signal amplifying means. An audio device comprising: a phase switching unit (14) for shifting a phase of an output signal with respect to an input signal between a signal amplifying unit and a sound output unit, wherein the signal level of the input signal reaches a predetermined level. The phase of the output signal is shifted from the input signal. According to a second aspect of the present invention, in the audio device according to the first aspect, the signal processing unit has a signal level adjusting unit (13) for adjusting a level of an input signal, and the predetermined level is set to a signal level adjusting unit. Is the level at which the operation starts. According to a third aspect of the present invention, in the audio device according to the first aspect, the phase switching means changes a delay time width of the phase switching according to the signal level.
According to a fourth aspect of the present invention, in the audio device according to the first aspect, the phase switching means switches the phase near a zero cross point after the input signal level falls below a predetermined level. An acoustic device according to a fifth aspect is the first aspect.
(3) The signal processing means according to any one of (3) to (3), further comprising a mute means (17) for muting the sound output. The sound device according to claim 6 is the sound device according to claim 1.
A sound device according to any one of claims 1 to 5 is provided.

According to the configuration of the present invention, when the amplified sound signal exceeds a predetermined signal level, the audio apparatus according to any one of the first to third aspects of the present invention uses the phase switching circuit to change the output signal. The phase switching is performed, the phase of the sound signal output from the speaker is inverted, and the sound signal input from the microphone is canceled so that the howling phenomenon hardly occurs. Particularly, according to the third aspect, the A / D
Since the delay time width of the sound signal output from the speaker with respect to the sound signal input from the microphone can be changed according to the signal level of the converted sound signal, the sense of incongruity due to a sudden change in the phase can be reduced. become. Further, the acoustic device according to the fourth and fifth aspects not only makes it difficult to cause the howling phenomenon, but also can reduce unnatural sound due to discontinuity of the sound output from the speaker.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. In this specification, the same or similar circuit elements are denoted by the same reference numerals throughout the drawings to simplify the description. In each of the operation timing diagrams ((a) to (c)) of each figure, a thin solid line S
i represents an input signal from the microphone, and a thick solid line S
"o" represents the output signal of the phase switching circuit, and the sound signal is simply shown as a sine wave of only about one cycle. FIG. 1 shows a configuration of a sound device 1 according to a first embodiment of the present invention and an example of operation timing thereof. Reference numeral 11 denotes a microphone (sound input means) for converting sound into an electric signal (sound signal), and reference numeral 12 denotes a converted sound. An amplifying circuit (amplifying means) for amplifying the amplified sound signal; 13, an automatic gain control (hereinafter referred to as "AGC") circuit (signal level adjusting means) for adjusting the amplified sound signal to a predetermined level; The phase of the sound signal output to the speaker is set to 180
A phase switching circuit (phase switching means) for converting the sound signal into a reversed phase signal (phase switching means), and a speaker (sound output means) 15 for converting a sound signal into sound again. The amplifier circuit 12 has an amplifier 12a whose output is feedback-connected to an inverting input via a resistor.
It is composed of With such a configuration, FIG.
As shown in (a), the signal level of the sound signal amplified by the amplifier circuit 12 is equal to the signal level (V
t), the phase switching of the sound signal by the phase switching circuit 14 is not performed, so that the signal Si and the signal S
A normal amplified output having no phase difference with o is performed. On the other hand, as shown in FIG.
When the signal level (Vt) at which the C circuit 13 operates is exceeded at time t1, the phase of the output signal is switched by the phase switching circuit 14, and then the sound signal So reaches the signal level at which the AGC circuit 13 operates. Until the phase switching is canceled after the non-performing period continues for a predetermined period, the phase of the sound signal So output from the speaker is inverted and output from the sound signal Si input from the microphone. By such an operation, even if the sound output from the speaker is too large and a part thereof is returned to the microphone,
Since the returned sound signal acts to cancel the signal level of the input signal, the howling phenomenon is less likely to occur. FIG. 2 shows an acoustic device 2 according to a second embodiment of the present invention.
1 is different from the first embodiment of FIG. 1 in that a level detection circuit 16 for detecting the output level of the AGC circuit 13 and controlling the switching operation of the phase switching circuit 18 is added. That is being done. With such a configuration, as shown in FIG. 2A, when the amplified sound signal So is a signal smaller than the predetermined voltage level Vth preset by the level detection circuit 16, the first embodiment As in the case of the embodiment, since the phase switching of the sound signal by the phase switching circuit 18 is not performed, the signal is amplified and output without a phase difference between the signal Si and the signal So. Then, as shown in FIG. 2B, when the output from the AGC circuit 13 exceeds a predetermined voltage level Vth, when the signal level reaches the vicinity of the zero crossing point (time t2), the phase switching circuit 18 , The phase of the signal So is switched.
Is inverted with respect to the signal Si and output.
By such an operation, a howling sound is hardly generated similarly to the first embodiment, and a sound with a pop-like discomfort due to a rapid change of the sound signal So is not generated. FIG. 3 shows a configuration of an acoustic device 3 according to a third embodiment of the present invention and an operation timing example thereof. The difference from the second embodiment in FIG. A mute circuit 17 for short-circuiting the sound signal to a predetermined level to mute the sound output is added. With such a configuration, as shown in FIG. 3A, when the amplified sound signal So is a signal smaller than a predetermined voltage level Vth preset by the level detection circuit 16, the first embodiment As in the case of the embodiment, the phase switching circuit 18
Is not performed, the signal is amplified and output without a phase difference between the signal Si and the signal So. Then, as shown in FIG. 3B, when the output of the AGC circuit 13 exceeds a predetermined voltage level Vth preset by the level detection circuit 16, the signal level of the signal So falls below a predetermined value. The mute operation is performed on the signal So near the zero crossing point (time t3) after the operation. After a predetermined period, when the mute operation is released in the vicinity of the zero cross point of the signal Si, the signal So whose phase has been inverted by the phase switching circuit 18 is output. Such an operation makes it difficult to produce a howling sound as in the first and second embodiments, and performs a continuity of sound by performing a mute operation when the sound becomes discontinuous due to a sudden change in the sound signal. Makes it difficult to feel the discomfort that accompanies. FIG. 4 shows a configuration of a sound device 4 as a fourth embodiment of the present invention and an example of its operation timing, where 21 is an A / D converter for converting a sound signal from the microphone 11 into a digital signal, and 22 is an A / D converter. A signal processing circuit for digitally processing a signal from the D converter, 23 is an AG of the first embodiment.
AGC phase switching circuit for digitally performing C operation and phase switching operation; 24, a D / A conversion circuit for re-converting a digital signal into an analog sound signal; 25, a speaker 15 in accordance with the D / A converted sound signal 1 shows a driving circuit for driving the. With this configuration, as shown in FIG. 4A, when the signal level of the A / D-converted sound signal is sufficiently smaller than the level (Vth) at which the AGC phase switching circuit 23 operates, The sound signal is not phase-switched by the AGC phase switching circuit 23, and is amplified and output without a phase difference between the signal Si and the signal So. And FIG.
As shown in (b), the signal level of the A / D converted sound signal is changed to the level (Vt) at which the AGC phase switching circuit 23 operates.
If the time is close to h), the phase of the output signal is delayed by about 90 ° (delay time td1) by the AGC phase switching circuit 23. Then, as shown in FIG.
If the signal level of the D-converted sound signal exceeds the level (Vth) at which the AGC phase switching circuit 23 operates, the AG
The phase of the sound signal So is set to 180 ° by the C phase switching circuit 23.
(Delay time td2) The phase is inverted with a delay. By such an operation, when the output sound from the speaker increases and the ratio of the feedback to the microphone starts to increase, the feedback amount is reduced so that the howling phenomenon does not easily occur, and the output sound from the speaker further decreases. When the feedback becomes larger and the howling phenomenon is more likely to occur, the occurrence of the howling phenomenon is suppressed as in the other embodiments. In the description of the present embodiment, AG
Although only one level at which the C phase switching circuit 23 operates is shown, a plurality of levels may be set, and the delay time width for phase switching may be changed according to each set level.

According to the configuration of the present invention, the sound device according to any one of the first to fifth aspects has a simple structure, but the sound from the speaker is increased and the sound is returned to the microphone. Even if the ratio increases, the returned sound signal operates so as to reduce the input signal level, and has an effect that the howling phenomenon hardly occurs. Furthermore, the acoustic device according to the third and fourth aspects can reduce discontinuity of sound output from the speaker, and thus can reduce unnatural sound due to discontinuity of sound. There is also an effect. In the hearing aid according to the sixth aspect, the howling phenomenon can be prevented with a simple configuration, so that the device can be easily reduced in size and cost, and the hearing aid can be used more safely. It has the effect of being able to do so.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an acoustic device of the present invention and an explanatory diagram showing its operation timing;

FIG. 2 is a configuration diagram showing a second embodiment of the acoustic device of the present invention and an explanatory diagram showing its operation timing.

FIG. 3 is a configuration diagram showing a third embodiment of the acoustic device of the present invention and an explanatory diagram showing its operation timing.

FIG. 4 is a configuration diagram showing a fourth embodiment of the acoustic device of the present invention and an explanatory diagram showing its operation timing.

[Explanation of symbols]

 1: Acoustic device (first embodiment) 2: Acoustic device (second embodiment) 3: Acoustic device (third embodiment) 4: Acoustic device (fourth embodiment) 11: Microphone (sound input) 12) Amplifying circuit (amplifying means) 13: AGC circuit (signal level adjusting means) 14, 17: Phase switching circuit (phase switching means) 15: Speaker (sound output means) 16: Level detecting circuit 18: Muting circuit

Claims (6)

[Claims] 1. A sound input means such as a microphone for converting a sound into an electric signal, a signal amplifying means for amplifying an input signal inputted from the sound input means, and a response to an output signal from the signal amplifying means. An audio apparatus comprising at least sound output means such as a speaker for outputting sound, comprising phase switching means for shifting a phase of the output signal with respect to the input signal between the signal amplification means and the sound output means. An audio device, wherein the phase of the output signal with respect to the input signal is shifted when the signal level of the input signal reaches a predetermined level. 2. The signal processing device according to claim 1, wherein the signal processing unit includes a signal level adjusting unit that adjusts a level of the input signal, and the predetermined level is a level at which the signal level adjusting unit starts operating. Item 3. The acoustic device according to Item 1. 3. The acoustic device according to claim 1, wherein the phase switching means changes a delay time width of the phase switching according to the signal level. 4. The audio device according to claim 1, wherein the phase switching means switches the phase near a zero crossing point after the input signal level falls below the predetermined level. 5. The acoustic apparatus according to claim 1, wherein said signal processing means includes a mute means for muting a sound output. 6. A hearing aid comprising the acoustic device according to any one of claims 1 to 5.