Hearing aid is a kind of small amplifying device for the hearing-impaired to compensate for hearing loss (totally deaf patients can't hear through hearing aids). Hearing aids can be divided into box hearing aids, back of ear hearing aids, in ear hearing aids, ear canal hearing aids, full ear canal hearing aids, 100% invisible hearing aids and so on from the perspective of wearing position and shape. These kinds of hearing aids have their advantages and disadvantages
Method / step
1. Box hearing aid
advantage:
① The earphone of the hearing aid is far away from the microphone, so the feedback sound is small.
② It has large volume and can be made into high power, which can meet the needs of deaf people with heavy degree of deafness.
③ The volume adjusting knob is large, easy to use and adjust, which is suitable for the elderly.
④ The battery and the machine itself are cheap and easy to maintain.
Deficiencies:
① Hearing aids and their wires can produce friction sound with clothes, which affects the identification of language.
② Hearing aids are placed in the pocket of the human body. The human body is equivalent to a barrier. The low-frequency part of the sound can be reflected to the microphone, which affects the high-frequency sound and makes it difficult for deaf children and deaf people to speak.
③ The wire obviously exposed the deaf, which did not meet the psychological needs of the deaf.
2. Back of ear hearing aid: (BTE)
advantage:
① No wires, small size, placed on the back of the head, easy to be covered by hair, not easy to be found.
② Because the hearing aid is placed behind the ear, the low frequency reflection of the human trunk is reduced, so the frequency response effect is better than that of the box hearing aid of the same specification.
③ Because the volume is larger than that of the in ear type, more complex circuits can be used in the design, which improves its performance and function. For example, a sound sensing coil can be added to make the deaf listen to the phone.
④ Binaural wear can produce binaural effect and improve hearing effect.
Deficiencies:
① Because the microphone is very close to the receiver, which can produce feedback, it is necessary to customize an ear mold which is consistent with the ear canal and concha cavity, and connect it with the hearing aid with a sound guide tube. The ear mold and the sound guide tube make the resonance peak value of the external auditory canal move to about 1000Hz, which makes the deaf not used to hearing. ② The long acoustic duct does not match the high frequency impedance of the ear canal and middle ear, which reduces the high frequency gain.
3. Customized hearing aids
advantage:
① Good collection and sound source location;
② High definition, high sensitivity, low distortion, strong sense of listening orientation, beautiful and comfortable;
③ Due to the removal of the concha cavity, the resonance effect of the external auditory canal can be brought into play, which is conducive to the compensation of high frequency.
Deficiencies:
① Small size, thin shell, and put into the deep part of the external auditory canal; the shell should be anti-seismic and anti allergic.
② Because of its small volume and small gain, it is suitable for moderate and severe patients;
③ Because the battery is small, the battery life is shortened, so it needs to be replaced more frequently; the optional range is narrow, and the adjustable range is less. (except for digital programming)
4. Invisible hearing aids
advantage:
① From the perspective of hearing compensation for patients, because of the deep wearing position of invisible hearing aids, it brings a series of acoustic advantages.
② High definition, high sensitivity, low distortion, strong sense of listening orientation, beautiful and comfortable effect; Helmholtz resonance effect, mirror effect, balloon effect can enhance the effect of hearing aids, especially the compensation of high-frequency part rich in sound information is better, so that patients can hear more clearly.
③ It is the smallest in volume, more hidden, deep in the ear canal, close to the tympanic membrane, clearer and more realistic; it can directly listen to the telephone or stethoscope; because it is placed inside the ear canal, it is less affected by wind noise. In addition, the invisible hearing aid is located in the deep part of the ear canal, mainly in the bone of the external auditory canal. When the patient makes a sound, the sound waves produced by the cartilage resonance of the external auditory canal wall leak out, while the sound waves produced by the bone vibration are less, so the ear blocking effect can be reduced. It makes the patients more comfortable to wear.
Deficiencies:
① It is small in size and placed in the deep part of the external auditory canal, so it is not easy to replace the battery; the shell is required to be anti-seismic and anti allergic.
② Because of its small volume and small gain, it is suitable for moderate and severe patients;
③ Because the battery is small, the battery life is shortened and needs to be replaced more frequently; the price is high.
