The role of vents in the selection of hearing aids
Stomata is an important component that affects the acoustic parameters of hearing aids. The second hole that opens in the hearing aid ear mold is the vent. The choice and adjustment of the venting holes play an important role in the selection of hearing aids.
The Hearing Hearing Center reminds you that a suitable vent can not only improve the comfort of the hearing aid, but also improve the sound quality. Conversely, if the vent is not suitable, it will be a feedback whistle from the hearing aid and make the wearer feel unnatural, causing the patient to refuse to use the hearing aid.
The acoustic effect of the vent is primarily to reduce the low frequency effects of the hearing aid. Because of the different lengths and diameters of the tubes, the hearing aids can produce different amounts of low frequency attenuation.
The vents allow the unamplified signal to enter the ear canal, especially when the gain of the hearing aid is small and the external signal is strong. It can also improve the ventilation in the ear canal, reduce the occlusion of the patient’s ear canal, reduce the humidity in the ear canal, and prevent the immediate infection of the hearing aid in patients with otitis media. Therefore, when choosing a hearing aid for patients with otitis media with hearing impairment, it is necessary to consider adding a vent.
1 and ventilating are used in the gambling effect. When a hearing aid is used in a patient with low frequency hearing loss, they often feel that they are unnatural and have an echo. This is because the volume of the ear canal becomes smaller after the patient wears the hearing aid, and the sound of the hearing impaired patient’s own voice is transmitted into the ear canal with a smaller volume as the skull vibrates. A low-frequency resonance is generated, which increases the intensity of the low-frequency sound, so the patient feels that the voice of his own voice becomes larger and shifts.
There are two ways to eliminate or reduce the betting effect: one is to increase the diameter of the vent and shorten the length of the vent to increase the attenuation of the vent to low frequencies. The second is to grow the ear canal portion of the eardrum so that it exceeds the cartilage portion of the ear canal. And the cartilage department is closely attached to reduce the amount of the patient’s own voice into the ear canal.
2, vent and feedback howling effect: When the selected vent of the eardrum does not match the gain of the hearing aid, the hearing aid will produce howling.
Impact of 3 and vents on hearing aid performance
(1) Effect on the internal noise of the hearing aid: The venting hole attenuates the low-frequency output of the hearing aid, and also reduces the internal low-frequency noise of the hearing aid. For patients with hearing impairment with low frequency hearing loss, it is beneficial to choose a larger vent when the hearing aid is selected.
Effect of (2) on hearing aid compressors: Vents have no effect on the compression of the hearing aid. However, when the hearing aid’s compressor is lowered, the patient still feels louder because the sound can enter the ear canal directly through the larger venting hole without passing through the microphone of the hearing aid, and the sound is not attenuated.
4, type of vent: Vents are divided into three types: parallel vents, Y-shaped vents, and external vents. Parallel vents are generally preferred during hearing aid selection. Because the use of a Y-shaped vent increases the loss of the high frequency signal of the hearing aid compared to a parallel vent. Y-type vents are only used if the eardrum has limited space, ie parallel vents cannot be used. If a Y-shaped vent is used, the eardrum should be made as close as possible to the inside of the ear canal when making the eardrum.
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