Hearing aid structure 2021

A hearing aid is essentially an electro-acoustic amplifier in which the acoustic signal is converted into an electrical signal by a microphone (microphone), amplified by an amplifier, and then reduced to an acoustic signal by a receiver and transmitted to the human ear. Hearing aids are mainly composed of microphones, amplifiers, receivers, batteries, various volume and tone control knobs and other components. In terms of shape, hearing aids can be divided into box-type hearing aids, behind-the-ear hearing aids, in-the-ear hearing aids, glasses-type hearing aids and bone-conduction hearing aids. Today, let’s talk about microphones, receivers and batteries among the hearing aid components.

Hearing aid structure
Hearing aid structure

Hearing aid microphone

Microphone noise consists of two parts: device noise and output noise. The microphone is the main component that generates the local noise of the hearing aid. The higher the microphone sensitivity, the more difficult it is to achieve low noise.

Defects of the microphone.

1, easy to corrode, microphones are precision accessories, long-term exposure to moisture, especially sweat is easy to make it corroded.

2, sensitive to vibration, such as the sound of rubbing hearing aids, direct body vibration (running on a hard plane), impact sound, etc.. These vibrations become a noisier sound when amplified.

3. susceptible to wind noise. When the wind hits the head, the ear or the hearing aid, the patient is likely to hear annoying low to medium frequency wind noise.

4、Susceptible to frequency response range. When the hearing aid collides with hard objects (such as falling on the ground, etc.) it will change the distance between the microphone and the inlet hole, and it will reduce the frequency response range of the hearing aid.

In order to solve the problem of the signal-to-noise ratio of hearing aids in noisy environments, directional microphone technology was born. The use of directional microphones enables hearing aids to amplify useful information and suppress noise, thus improving speech intelligibility in noisy environments. Dual-microphone hearing aids are more effective than single-microphone hearing aids in terms of noise reduction.

Hearing aid receiver

A receiver is a device that converts electrical energy into acoustic energy. The frequency response of behind-the-ear hearing aid receivers is about three resonance peaks at 1KHz, 3KHz, and 5KHz. These resonance peaks are mainly caused by the sound transmission tube, including the short tube in the hearing aid, the ear hook, and the flexible tube connected to the earmold; the frequency response of canal hearing aid receivers has only two resonance peaks, one at 2.2~3KHz, and one at 5KHz. The resonance frequency can be adjusted by using different types of receivers.

As the frequency response width of the amplifier and microphone of the hearing aid can meet the requirement of 200Hz~8KHz, the frequency response width of the hearing aid mainly depends on the frequency response width of the receiver.

The receiver is the main component that produces the harmonic distortion of the hearing aid. As the output sound pressure level increases, the degree of distortion also increases, i.e. the louder the hearing aid, the greater the distortion. This is the reason why many patients who wear extra high-powered hearing aids all year round tend to speak unclearly, i.e. with a “big tongue”.

The narrower the bandwidth of the receiver, the less likely the hearing aid is to produce acoustic feedback whistling, so many hearing aids will deliberately limit the output bandwidth of the receiver, the common effective output bandwidth is 0.2~5.2KHz. The wider the compensation, the higher the resolution of the consonants, so they believe that hearing aid users with high-frequency compensation of 8KHz have better speech understanding. However, there is still a need to improve the technology to achieve both super bandwidth and anti-feedback whistling.

Hearing aid battery

Currently, the most widely used hearing aids are zinc-air batteries, which generate 1.4V through a lasting chemical reaction with oxygen in the air. Hearing aid batteries can be divided into four categories: A675, A13, A312, and A10 batteries. Each type of battery can be used for different lengths of time, A10 battery can be used for the shortest time, basically about 5 days; A312 battery can be used for 7-10 days, A13 battery can be used for 12-15 days, A675 battery can be used for the longest time, 20-25 days; now there are also some hearing aids can be charged directly, using the matching charging base for charging, generally charging once can be used for 8-10 hours. They can be used for 8-10 hours per charge.

HearingAidsElite

Hearing Aids Elite’s mission is to provide people with low-cost hearing aids that can help those who struggle with hearing loss enjoy a better quality of life. We not only make some of the world’s highest quality hearing aids but through innovation and uncompromising manufacturing standards, we provide those hearing aids at an accessible, affordable price for all, regardless of economic status.

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