Five factors affecting the sound quality of hearing aidsCindy
As a professional hearing aids manufacturer, Jinghao Medical combines its own years of R&D and production experience to summarize the following factors affecting the sound quality of hearing aids, mainly in the following aspects:
First, the hearing aid background noise: background noise has a great impact on users with better hearing or better frequency, and some high-end hearing aids have a noise floor as low as 14dB.At the same time, it is necessary to distinguish the difference between ambient noise and background noise. For example, some high-end hearing aids have a compression threshold as low as 20 dB, and small sound amplification is sufficient, but normal people may sound very noisy and feel noise.
Second, the frequency response range of hearing aids: We know the frequency range that can be heard by normal human ears: 20Hz-20KHz, the frequency range of speech: 200Hz-8KHz.The wider the frequency response of the hearing aid, the less likely it is to feel the horn sound, and the more natural and realistic the sound is, the higher the frequency response curve of the high-end hearing aid can reach 7000 Hz.
Third, the response speed of the hearing aid: the slow response speed causes the sound to sound soft, the feeling is not strong, the sound is faint, and it is easy to produce echo.People with better bone conduction or low frequency are more obvious.In general, the low frequency response speed of the sound is slower than the higher frequency response.Therefore, some hearing aid users with low frequency hearing and high frequency difference are more likely to feel the echo feeling and the sound is not clean and unclear.
Fourth, the nonlinear distortion of the hearing aid: including the distortion caused by digital processing technology, the distortion caused by nonlinear amplification and the distortion caused by some noise reduction processing.The “high sampling rate” analog-to-digital conversion reduces distortion of the hearing aid’s sound; “high-bit” analog-to-digital conversion reduces distortion caused by loud input.
Fifth, compression technology: In the end is fast compression or slow compression?Fast and slow compression has its advantages. In general, slow compression technology is more conducive to optimal language linear reduction. The speech signal has strong contrast and high definition, but in some specific cases, fast compression is necessary.
A qualified hearing aid should consider at least the following five performance indicators
1. frequency range.The frequency range of low-grade hearing aids is at least 300-3000 Hz, the high frequency of ordinary hearing aids should reach 4000 Hz, and the frequency range of advanced hearing aids can be between 80-8000 Hz.
2. maximum sound output or saturated sound pressure level (SSPL).It actually represents the maximum power output of the hearing aid.The maximum acoustic output when using a hearing aid should be lower than the discomfort threshold of the affected ear, especially for the ear that is positive for re-vibration, and the maximum acoustic output must be controlled to protect the affected ear.
3. maximum sound gain.It mainly represents the amplification capability of hearing aids, and the hearing aid gains produced by various countries are mostly between 30 and 80 dB.Generally speaking, if the degree of deafness is light, the gain should be selected to be small, and the hearing aids with medium gain or large gain should be selected respectively.In the specific use, the volume adjustment switch for varying the acoustic gain within a certain range is provided on the hearing aid.The choice of suitable hearing aids can be pre-calculated according to some formulas. The easiest way is to adjust the gain compensation of three audios of 500, 1000, 2000Hz according to the pure tone audiogram. It is better to use half or more of the threshold. Satisfactory effect.
4. frequency response and tone adjustment.In order to meet the hearing requirements of the deaf, the hearing aid should provide a variety of different frequency responses, and the different responses of the frequency are different in tone.In order to make the frequency response of the hearing aid more in line with the hearing loss characteristics of the deaf person, some different tones are set on the tone adjustment button, usually L stands for bass, N is normal, and H is high.
5 .signal to noise ratio (S / N).The amplified output of the hearing aid earphones is often accompanied by both linguistic signals and annoying noise. The greater the signal-to-noise ratio, the better the quality of the language information output.The signal-to-noise ratio of high-quality hearing aids can reach about 40dB, and at least 30dB should be guaranteed.