JPH0622397A - Hearing aid - Google Patents

Abstract

PURPOSE:To prevent the generation of a howling by coping with the momently varying change of an acoustic coupling by a simple constitution at a low cost. CONSTITUTION:Based on an electric signal PS from a microphone 1, the generation of the howling and the frequency are detected by a howling detecting part 7. The frequency of the electric signal is phase-shifted by a phase shifting part 3 according to the detected howling frequency, and the phase-shifted signal is added to the electric signal PS by a signal adding part 4. The added electric signal is converted into an acoustic signal by a receiver 6, and outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hearing aid which receives a voice signal with a microphone and amplifies the output signal with an amplifier or the like to drive a sounding body.

[0002]

2. Description of the Related Art In a conventional acoustic signal processing circuit in a hearing aid, the frequency characteristic of an amplifier circuit is controlled, for example, in order to compensate for the hearing loss characteristic of the user or to improve the hearing of consonants. As a circuit configuration for controlling such frequency characteristics, a low pass filter (LP
F), a high-pass filter (HPF) or a band-pass filter (BPF) is used to cut off a specific frequency, or a gain control circuit (AGC) is provided to mitigate an impulsive sound that is input unexpectedly. Has a built-in circuit for preventing howling that occurs when the hearing aid is attached and detached. Of these, howling that often occurs in a hearing aid is a kind of oscillation phenomenon that includes feedback of an acoustic signal. Therefore, it is possible to suppress howling by suppressing the center frequency of the oscillation with a band elimination filter.

That is, there is a possibility that howling can be prevented by inserting the band elimination filter into the amplification circuit of the hearing aid. A filter considered for such a purpose is, for example, a twin-T circuit (notch filter) as shown in FIG. 13, and an active filter (not shown) is a state variable band elimination filter.

A howling prevention circuit as shown in FIG. 14 has also been proposed. That is, in this example, the output signal from the microphone 50 is amplified by the amplifier 51, and the receiver (sounding body) 52 is driven by the amplified signal,
The input voice 57 input to the microphone 50 is amplified and output as the output voice 56. Here, the detection unit 55
Is composed of, for example, a pressure-sensitive switch or the like for detecting that the hearing aid is reliably inserted into the ear canal.
3 (switch or volume etc.) is controlled. As a result, the output of the amplifier 51 is output to the receiver 52 and is output as the sound 56 only after the hearing aid is securely inserted into the ear canal, so that the feedback of the acoustic signal from the receiver 52 to the microphone 50 is prevented. It suppresses howling.

[0005]

However, in the conventional signal processing circuit, for example, in the case of FIG. 14, although the structure is certainly simple, for example, when the signal processing unit 53 is composed of a switch, the detection unit is If 55 is not detected that the hearing aid is securely inserted in the ear canal, the switch is turned off and the output sound 56 is not output, so that nothing is heard, and even if it is composed of the volume, the detection unit 55
If is not inserted into the ear canal surely, the volume of the signal processing unit 53 is reduced and the output sound 56 becomes small, so that it is difficult to hear. If such a circuit configuration is limited only when the hearing aid is attached / detached, there is no inconvenience even if the output sound is not heard, so it is certainly effective.
For example, when howling occurs due to sound leakage due to a change in the ear canal, such as during a meal, the detection unit 55 detects that the sound is inserted into the ear canal, and thus the signal processing unit 53. It is impossible to suppress howling by shutting off or turning off the volume or the like, and this howling causes a problem that the user cannot hear the external sound.

When the signal processing section 53 of FIG. 14 uses a filter circuit as shown in FIG. 13, a detecting section 55 is used.
Is detected as not being inserted in the ear canal,
However, when the path of acoustic return changes momentarily due to the movement of the jaw, such as during meals,
Since the howling frequency changes every moment, it is necessary to change the frequency characteristic of the filter accordingly. However, even the filter as shown in FIG. 13 or the above-mentioned state change type filter cannot change its frequency characteristic in correspondence with the howling frequency.
It should be noted that this frequency characteristic is electrically changed (controlled).
However, there is a problem that the circuit configuration for that is complicated and the hearing aid itself becomes expensive.

The present invention has been made in view of the above-mentioned conventional example, and provides a hearing aid having a simple and inexpensive structure and capable of preventing the howling from occurring by responding to the change of the acoustic coupling which changes from moment to moment. With the goal.

[0008]

In order to achieve the above object, the hearing aid of the present invention has the following configuration. That is,
A hearing aid used partially or wholly inserted into the ear canal, which comprises a conversion means for inputting an acoustic signal and converting it into an electric signal, and a detection means for detecting howling and its frequency based on the electric signal. A phase shifting means for shifting the frequency of the electric signal from the converting means according to the howling frequency detected by the detecting means, a signal phase-shifted by the phase shifting means and an electric signal from the converting means And addition means for adding and, and a sound generation means for converting the electric signal added by the addition means into a sound signal.

Further, the phase shift means has a first-order lag type all-pass filter.

Further, switch means is further provided between the phase shift means and the adder means, and a signal phase-shifted by the switch means or a signal non-phase-shifted can be selectively output.

[0011]

In the above structure, an acoustic signal is input and howling is generated and its frequency is detected based on the electric signal. In accordance with the detected howling frequency, the frequency of the electric signal is phase-shifted, the phase-shifted signal and the electric signal are added, and the added electric signal is converted into an acoustic signal and output.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the schematic arrangement of a hearing aid according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 is a microphone for inputting external sound and converting it into an electric signal for output, and reference numeral 2 is a preamplifier for amplifying the output signal of the microphone 1. 3 is a phase shifter, which outputs the output signal P _S of the preamplifier 2,
The control signal V _C from the control unit 8 is input, and a phase shift output signal SS that outputs the phase of the output signal P _{S in accordance} with the control signal V _C is output. Reference numeral 4 denotes a signal adder, which inputs the phase shift output signal SS and the output signal P _S and adds these two signals. 5 is a power amplifier,
The addition output MT of the signal addition unit 4 is input and amplified, and the receiver 6 in the subsequent stage is driven to output an acoustic signal. 7
Is a howling detector, which is an output signal P from the preamplifier 2.
Input _S to detect if howling is occurring in this hearing aid. A suppression control unit 8 receives the howling detection signal (frequency) from the howling detection unit 7, and controls the shift amount of the phase shift unit 3 by the control signal V _C. The portion 9 shown by the dotted line in FIG.
A signal suppression unit that includes a phase shift unit 3, a signal addition unit 4, and the like and suppresses a specific frequency signal is shown.

FIG. 2 is a block diagram showing the circuit configuration of the signal suppressing section 9 which is the main part of this embodiment. The parts common to those in FIG. 1 are designated by the same reference numerals, and their description will be omitted.

In FIG. 2, 10 and 11 are operational amplifiers (hereinafter referred to as operational amplifiers) having an inverting input terminal (-), a non-inverting input terminal (+) and an output terminal, and the operational amplifier 10 has resistors R ₁ , R ₂ and a capacitor. The phase shifter 3 is provided with C and a voltage variable resistance element (hereinafter, VCR), and constitutes a so-called first-order lag type all-pass filter. Further, the operational amplifier 11 forms an addition amplifier by inputting the output signal P _S to the inverting input terminal via the resistor R ₃ and also inputting the output signal of the operational amplifier 10 to the inverting input terminal via the resistor R _4. Then, the signal adder 4 is configured.
The VCR 12 is controlled by the control signal V _C from the control unit 8.
The resistance value can be changed.

FIG. 3 is a diagram showing frequency characteristics of the suppressed signal in the signal suppressing section 9. In FIG. 3, the vertical axis represents the output signal level (corresponding to the addition signal MT) and the horizontal axis represents the frequency. As will be described later in detail, the suppression frequency f _{H on} the horizontal axis corresponds to the control signal V _C from the control unit 8 and is VCR.
It is changed by changing the value of 12.

Next, the operation of the hearing aid of this embodiment will be described with reference to FIG.

A part of the output sound of the receiver 6 is
If howling occurs when you return to Hon 1, howe
The ring detector 7 detects this and suppresses the frequency.
Output to the unit 8. As a result, the suppression control unit 8
Control signal V for the switching frequency _C Is output. Receive this
The phase shifter 3 has a frequency (ω₀ )
Change and suppress frequency f_H Matched to howling frequency
Let As a result, the output signal P_S And 90 degrees phase delayed
Since the phase shift output signal SS is added by the signal addition unit 4,
Howling is reduced because the signal component of the howling frequency is attenuated.
Stop.

FIG. 4 is a circuit diagram showing the basic structure of the above-mentioned first-order lag type all-pass filter, FIG. 5 is a diagram showing the phase characteristic of this circuit, and FIG. 6 is a diagram showing its frequency characteristic.
The VR shown in FIG. 4 represents a variable resistor, and the VR shown in FIG.
It corresponds to 12.

As shown in FIG. 5, the phase shifter 3 and the first-order lag type all-pass filter shown in FIG. 2 are delayed by 90 degrees at a frequency ω _{0 with} respect to a predetermined VR value in the circuit shown in FIG. , As the frequency approaches “0”, the phase approaches 0 degrees, and conversely, when the frequency approaches infinity (∞), the phase becomes −18.
It has a characteristic of approaching 0 degree. On the other hand, the frequency characteristic shown in FIG. 6 maintains a constant output regardless of the change in frequency (change in VR). Therefore, by changing ω ₀ by changing the value of VR, it is possible to make the output level constant and change only its phase.

Next, the operation of the signal adding section 4 will be described with reference to FIG. As shown in FIG. 2, the signal addition unit 4
Inputs the output signal P _S of the preamplifier 2 and adds it to the output signal SS of the phase shift unit 3. Here, of the frequency components of the output signal P _S, the amount of phase shift is small in the low frequency range (0 side), and the amount of phase shift approaches −180 degrees in the high frequency range (infinity side), so there is no phase shift. By adding the output signal P _S and the output signal SS, the higher the high frequency region is, the higher the cancellation rate becomes, and the frequency characteristic shown in FIG. 3 is obtained. Therefore, the output can be suppressed on the higher frequency side than the frequency f _{H in} FIG.

Here, as described above, VCR1
Since the resistance value of 2 changes according to the control signal V _C , it has the same effect as the variable resistor VR shown in FIG. 4, and the suppression frequency f _H can be changed by the control voltage V _C.

FIG. 7 is a diagram showing a circuit configuration of another embodiment in which the above-mentioned first-order lag type all-pass filters are connected in series in two stages to configure the phase shifter 14 corresponding to the phase shifter 3. .

The resistor R ₁₁ is connected to R ₁ , the resistor R ₁₂ is connected to R ₂ , the variable resistor VCR 120 is connected to VCR 12, and the capacitor C _{1 is connected.}
Corresponds to C, and the operational amplifier 13 corresponds to the operational amplifier 10. Further, the control signal V _C from the suppression control unit 8 is
In this example, it is supplied in parallel to the VCR 12 and the VCR 120. It should be noted that these may be controlled separately or may be different control signals.

FIG. 8 is a diagram showing a phase shift characteristic of the circuit shown in FIG.

The amount of phase shift here is, of course, as shown in FIG.
It has doubled compared to. That is, it is configured such that a doubled amount of phase shift can be obtained corresponding to the same change in frequency.

FIG. 9 is a diagram showing the frequency characteristic of the frequency suppressing unit 9 when the phase shifting unit 14 of FIG. 7 is applied to FIG. 1 or 2.

The operation of the circuit shown in FIG. 7 will be described. As described above, the frequency ω ₀ 'where the phase amount in FIG. 8 becomes -180 degrees.
Since the ratio of the output signal P _S and the output signal SS of the phase shift unit 14 canceling each other becomes maximum, the phase shift unit 14 of FIG.
When applied to the suppression control unit 8 and the phase shift unit 3 in FIG. 1 or 2, a kind of notch characteristic as shown in FIG. 9 is obtained. By changing the control signal V _C here, VCR1
2. As described above, the resistance value of the VCR 120 changes, and as a result, ω ₀ 'and f _H ' can be changed.

FIG. 10 is a block diagram showing the configuration of the signal processing circuit of the hearing aid of another embodiment in which the switch unit 15 is provided between the phase shift unit 3 and the signal addition unit 5.

In FIG. 10, reference numeral 15 is a switch unit, and the switch SW1 has a common contact connected to the first input terminal of the signal addition unit 4 and a first contact connected to the output signal P _S which is an input of the phase shift unit 3. The second contact is grounded. On the other hand, the common contact of the switch SW2 is the second contact of the signal adding section 5.
It is connected to the input terminal, the first contact is grounded, and the second contact is connected to the output terminal of the phase shift unit 3 (14).

FIG. 11 is a diagram for explaining the operation mode of the switch section 15.

In FIG. 11, mode A (through) is
The switch SW1 is connected to and the switch SW2 is connected to and, and at this time, the signal addition unit 4 outputs the output signal P _S as it is as MT. Next, in the mode B (notch), the switch SW1 is connected to-and the switch SW2 is connected to-and the circuit configuration shown in FIG. 1 or 2 is the same.

Mode C (phase shift) is equivalent to a state in which the switches SW1 and SW2 are both connected to-and the signal adding section 4 of FIG. 1 is omitted.

Next, the operation of the circuit shown in FIG. 10 will be described.

Since the phase shift output signal SS can be selectively input to the signal addition section 4 by the switch section 15 between the phase shift section 3 and the signal addition section 4, for example, the mode A
Is used when no howling is occurring, and at this time, only the output signal P _S can be input to the signal adding section 4.
Therefore, the sound quality does not deteriorate.

When light howling is occurring, mode C is used to shift the phase of the input signal P _S , thereby shifting the phase of the sound returned to the microphone 1 and suppressing howling.

The mode B is used for heavy howling. In this case, howling can be suppressed by the characteristics shown in FIG.

As described above, according to the present embodiment, as shown in FIGS. 2 and 7, the phase shifters 3 and 14 can be constructed extremely simply, and the signal suppressor 9 can also be simplified. Further, as described above, there is an advantage that the suppression frequency can be easily changed and a good howling suppression characteristic can be obtained although the configuration is simple.

Further, as shown in FIG.
Since the suppression effect corresponding to the situation can be obtained by providing, the problem that the sound quality is unnecessarily deteriorated in order to obtain a sharp suppression characteristic can be eliminated.

It is widely known that the notch filter shown in the conventional example can obtain a simple and sharp suppression frequency, but it is difficult to select the value of the element and it is difficult to make it a variable characteristic. In comparison, the present embodiment is simple and the characteristics can be changed electrically easily.

In the above description, the delay type first-order all-pass filter is used as the basic element of the phase shift section. However, the same applies when a phase-advancing all-pass filter is used as shown in FIG. 12, for example. The effect is obtained.

As described above, according to the present embodiment, the signal detected by the microphone is phase-shifted by the phase-shifting means and the original signal not passing through this phase-shifting means is added to obtain a specific signal. Since the frequency signal can be suppressed, the suppression characteristic can be sharpened with a simple structure. Further, since the frequency of phase shift can be freely changed by a control signal from the outside, it is possible to cope with a change in the acoustic coupling that changes from moment to moment.

[0044]

As described above, according to the present invention, it is possible to prevent howling from occurring by responding to the change of the acoustic coupling which changes momentarily with a simple and inexpensive structure.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a signal processing circuit of a hearing aid according to an embodiment of the present invention.

FIG. 2 is a diagram showing a circuit configuration of a signal suppressing section shown in FIG.

FIG. 3 is a diagram showing frequency characteristics of the circuit shown in FIG.

FIG. 4 is a circuit diagram showing a configuration of a first-order lag-type all-pass filter which is a basic configuration of a phase shift unit of the present embodiment.

5 is a diagram for explaining the phase characteristics of the circuit of FIG.

6 is a diagram showing frequency characteristics of the circuit of FIG.

FIG. 7 is a block diagram showing a circuit configuration of a phase shifter according to another embodiment of the present invention.

8 is a diagram showing phase characteristics of the phase shift unit of FIG.

9 is a diagram showing frequency characteristics of the phase shift unit of FIG. 7.

FIG. 10 is a block diagram showing a configuration of a signal suppressing unit according to another embodiment of the present invention.

11 is a diagram for explaining an operation mode of the circuit of FIG.

FIG. 12 is a circuit of a first-order phase advance type all-pass filter which is a modification of the basic configuration of the phase shift unit of the present embodiment.

FIG. 13 is a diagram showing a circuit example of a conventional notch filter.

FIG. 14 is a diagram showing a configuration of a conventional howling prevention circuit.

[Explanation of symbols]

 1 Microphone 2 Preamplifier 3 Phase shifter 4 Signal adder 5 Power amplifier 6 Receiver (speaker) 7 Howling detector 8 Suppression controller 10, 11, 13 Operational amplifier 12,120 VCR (voltage variable resistance element) 15 Switch

Claims (1)

[Claims] 1. A hearing aid which is partially or wholly inserted into an ear canal for use, comprising: a conversion means for inputting an acoustic signal and converting it into an electric signal; and howling and its frequency based on the electric signal. Detecting means for detecting, phase shifting means for shifting the frequency of the electric signal from the converting means according to the howling frequency detected by the detecting means, the signal shifted by the phase shifting means and the conversion A hearing aid, comprising: an addition unit that adds the electric signal from the unit, and a sound generation unit that converts the electric signal added by the addition unit into an acoustic signal.