Classification by hearing aid conduction mode: \ x0d \ x0d \ According to hearing aid conduction mode, hearing aid equipment can be divided into air conduction hearing aid, bone conduction hearing aid and tactile hearing aid. \x0d\ 1。 Air conduction hearing AIDS are widely used at present, which transmit sound into the inner ear through air conduction. \x0d\2。 Bone conduction hearing aid is a hearing aid that transmits sound into the inner ear through the conduction of bones (mastoid, teeth, ossicles, etc.). ). Bone conduction hearing AIDS are mainly used for people with severe conductive hearing impairment, as well as deaf people who cannot use air conduction hearing AIDS such as inflammation of external auditory canal, active suppurative otitis media, bilateral external ear atresia and deformity. This kind of hearing aid can be glasses, hairpin or implanted, so that the receiver can be attached to the mastoid or ossicle. Generally speaking, bone conduction hearing AIDS are not widely used. \x0d\3。 Tactile hearing AIDS, also called vibrating hearing AIDS, are similar to box hearing AIDS. It uses a vibrator instead of headphones. When it is used, it is worn on the wrist like a watch, and the sound can be understood through the changing touch of vibration. This kind of hearing aid is for people with severe deafness. Because vibrators need strong power amplification, the effect of sensing language signals through touch is not good, so they are generally not popularized. \ x0d \ x0d \ Classification according to its technical principles \ x0d \ x0d \ Hearing AIDS are divided into electric hearing AIDS, electron tube hearing AIDS, semiconductor hearing AIDS, integrated circuits and programmable hearing AIDS according to their technical principles. \x0d\ If hearing AIDS are classified according to the degree of using digital electronic technology, then hearing AIDS before integrated circuit hearing AIDS all use analog electronic components. Starting from the programmable hearing aid, digital electronic chips enter the hearing aid to control the work of other analog components, which is called digital-analog mixed circuit. \x0d\ After measuring the static frequency response of hearing AIDS with various devices, people pay more attention to the dynamic characteristics of hearing AIDS, because the sound people are exposed to every day is a signal whose intensity and frequency are changing dynamically. According to its dynamic frequency response characteristics, hearing AIDS can be divided into two categories: \ x0d \ x0d \ (1) ffr (fixed frequency response, fixed). At present, most hearing AIDS on the market are of this kind, and their frequency response characteristics have been determined when the products leave the factory. The tone knob on the hearing aid can only change its frequency response characteristics to a certain extent. After the hearing aid parameters are selected, the frequency response of the hearing aid is fixed no matter what environment the user is in. \ x0d \ (2) LDFR (Level Independent Frequency Response) hearing aid. The hearing aid with K-AMP circuit is a typical TILL type, while the wide dynamic range compression circuit in most programmable hearing AIDS is a more accurate LDFR type. \x0d\\x0d\ Digital hearing AIDS: For patients with high hearing recovery requirements, digital hearing AIDS can be selected. The features of this hearing aid are: \x0d\\x0d\( 1) further increases the flexibility of compression characteristic control, and adjusts the inflection point and compression ratio of hearing aid compression; \x0d\(2) The gain and frequency response of the hearing aid can be automatically processed, and the gain and compression characteristics of different frequency bands can be set in different channels according to the hearing loss characteristics of the hearing impaired. \x0d\(3) The gain of sound in different directions can be automatically controlled in a nonlinear way to minimize noise; \x0d\(4) Digital acoustic feedback control can effectively improve the gain; \x0d\(5) Compared with analog hearing AIDS, the same sound processing reduces the energy consumption of the battery; \x0d\(6) Digital dual microphone automatic correction function intelligently controls sound gain in different directions; \x0d\\x0d\(7) Low-voltage prompting function of digital hearing aid, which is more convenient for battery replacement, anti-electromagnetic interference function, and clearer for calling mobile phone. \x0d\ programmable hearing aid: The programmable hearing aid is adjusted by Bellevue Company in 1988 according to computer programmable means, which has many advantages that the adjustable hearing aid does not have: \x0d\( 1) Multi-channel processing digital chip can divide the frequency range into multiple channels, and determine their gain, compression threshold and compression ratio respectively, and the range of channels can be divided freely. \x0d\\x0d\(2) The fine-tuning digital chip can control more than a dozen hearing aid parameters. Programmable hearing AIDS can adapt to hearing impaired people with different degrees and hearing curve types. \x0d\(3) The compression ratio can be adjusted. The compression ratio of traditional compression amplification hearing AIDS is fixed when they leave the factory, which does not necessarily match the specific loudness growth of each hearing impaired person. The digital chip makes the compression ratio adjustable. \x0d\(4) Selection of multiple programs. These settings can ensure the use in various acoustic parameter environments. Hearing aid users can freely choose the best listening effect by programming several specific programs and a switch that can be switched at any time in a quiet office and a noisy market. \x0d\(5) Wide Applicability Programmable hearing AIDS are widely used in various hearing loss curve types and different properties, such as flat, sloping, conductive, sensorineural or mixed deafness.