What is the application of inductor coils in hearing aids?

Inductor coil is a hearing aid device for receiving magnetic signals. When there is an alternating magnetic field in the surrounding environment, the coil can induce this magnetic force to generate an electric current, which is finally converted into sound by the microphone and transmitted to the human ear.

1. How does the inductor coil work?

The figure below shows the schematic diagram of the inductive coil in the hearing aid.

M means "microphone" and T means "inductive coil". When the hearing aid is in the M position, the coil does not work; when the hearing aid is in the T position, the coil can identify the magnetic signal in the surrounding environment and amplify it into an electrical signal of the same size, which is further converted into a sound that the human ear can recognize. The stronger the magnetic signal, the clearer and more realistic the sound is heard.

2. Which hearing aids have an inductive coil function?

1) behind-the-ear hearing aids

Behind-the-ear hearing aids are larger in size, easier to operate, and easier to install inductive coils.

2) Some customized hearing aids

Some ITEs and ITCs can be equipped with an inductive coil function. CIC generally does not have an inductive coil function due to its small size.

Instructions

A. Manual switch

There are usually two ways to manually switch:

1) Select directly on the hearing aid body: suitable for some hearing aids with "O, T, M" installed;

2) Switching program button: suitable for hearing aids with inductive function programs (dispensers need to set them in advance).

B. Automatic switching

For some higher-end hearing aids, as long as the inductance function is preset by the dispenser, the hearing aid can switch automatically when it senses the magnetic field environment, without the need for manual settings by the user.

3. What functions can the inductor coil achieve?

Function 1: Answer the phone

The picture below is a behind-the-ear hearing aid with a "T-stop" function. As seen in the picture:

M Microphone Program

Hearing aid microphones work normally, picking up sounds from the surrounding environment.

T Inductive Phone Program

The hearing aid microphone does not work, the hearing aid only picks up the magnetic signal from the phone or cell phone.

OTurn off hearing aids

Tips:

In addition to O, T, M, some hearing aids come with MT and mT.

Both MT and mT belong to the mixed mode of microphone and inductor.

MT means that the sound heard through the microphone and the inductor is equal in magnitude, and mT means that the sound heard through the microphone is smaller than that in the induction telephone.

Function 2: Induction loop magnetic signal

The induction loop system converts the audio signal into an electric current, which in turn generates a magnetic field for the induction loop in the hearing aid to recognize.

As can be seen in Figure a below, the loop coil system is laid throughout the room.

When the speaker begins to speak, the loop coil converts the audio signal into an electrical current, which in turn generates an alternating magnetic field.

When the inductive coil in the hearing aid recognizes this magnetic signal, the inductive coil converts it into sound and transmits it to the human ear through the receiver.

4. The influence of the magnetic field size on the inductor coil

Ideally, only when the magnetic field strength of the telephone device reaches 100 mA/m, the inductive coil can effectively receive this magnetic signal and convert it into sound for the hearing aid user to hear.

For most of today's telephone equipment (such as landline phones, mobile phones, etc.), the magnetic field strength generated by them is difficult to reach 100 mA/m.

Therefore, some hearing aid users with severe hearing loss may feel that the sound is a little weak when using the inductance to make calls, which cannot meet their hearing loss needs.

To improve this phenomenon, hearing aid users can attach a magnet to the earpiece of a telephone or mobile phone, thereby enhancing the magnetic field of the telephone equipment, so as to improve the listening effect of the induction telephone.

The relatively small number of signal transitions of the inductive coil results in less distortion, greater signal-to-noise ratio, and more comfortable listening.

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