Huizhou Jinghao Medical Technology CO., Ltd.

The Working Principle of Analog Hearing Aids

With the development of microelectronic technology, hearing aid has been miniaturized.
There are four basic types of hearing aids: case, eyeglasses, and ear - level back and inner (ear canal). The box is large in size, convenient in use and cheap in price. It is suitable for the elderly, children and the severely deaf. Ear hearing aids have developed rapidly since 1980s. The inner ear type is customized according to the shape of the user's ear shell cavity and ear canal. It has good effect and is relatively hidden. Now it can produce high power, which is welcomed by the deaf.
Working principle of analog hearing aid:
The analog circuit works directly and stably, with little distortion. The sound in the hearing aid is converted into a continuously changing electrical signal through the microphone. This signal is filtered, amplified and then converted into sound signal by the receiver into the ear. The internal circuit used for filtering and amplification is the analog circuit. Volume adjustments are usually analog settings, and fine-tuning with a screwdriver can process sound signals by changing a small variable resistance value. Analog hearing aids can be classified into A, B and D according to the type of amplification circuit used. There is also a hybrid circuit of nonlinear amplification, that is, class K circuit, commonly known as Wide Dynamic Range Compression Circuit (WDRC). In a simulated hearing aid circuit, each element has its specific function. The different parameters of components will directly affect the performance of hearing aids. In other words, in order to change the characteristics of hearing aids, we must change the parameters of components in the circuit. There is no software involved in the signal processing of the simulator, so different performance analog hearing aids must have different physical components, which is the biggest difference from digital hearing aids.
The basic structure of hearing aid includes four main parts: microphone, amplifier, earphone and power supply. The hearing aid converts the sound signal into an electrical signal into an amplifier, which amplifies the input weak electrical signal and then passes it to the output transducer. Output transducer is composed of earphone or bone vibrator, whose function is to convert the amplified strong signal from electric energy to sound signal (sound energy) or kinetic energy output. Therefore, the signal from the headset or bone vibrator is much stronger than the original signal received by the microphone, which can compensate the hearing loss of the hearing-disabled to different degrees.

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