Hearing Aid Performance Selection Fitting guide

The electroacoustic parameters of hearing aids include gain, frequency response, compression ratio, number of channels, and so on. However, not all of these properties are necessary, so it is necessary for audiology professionals to determine the required performance when assisting patients in choosing the right hearing aid. The selection of common hearing aid performance is as follows.

1. volume control

Although the use of automatic gain control hearing aids and multi-program hearing aids has become more common and patients’ demand for volume control is gradually decreasing, in fact, some patients explicitly require hearing aids with volume control, including some already using automatic gain control hearing aids User. Some of them are because of habits, some are by accident, some are because they need their own ability to control hearing aids, some are afraid of computer programming, and so on.
Although there is no effective method for assessing which patients need volume control, this process can be negotiated with patients to reach a consensus.

2. Inductive pickup

For patients with severe and severe deafness, inductive pickup is a basic performance requirement. It can also help people with moderate hearing loss to use the phone. People with mild hearing loss can handle calls without using hearing aids. Patients with any degree of hearing impairment like the sound provided by the inductance in the loop coil with very little noise and reverberation. Of course, its disadvantage is that it increases the volume to accommodate the inductor and the switch, and increases the congestion of the in-ear and ear canal hearing aid panels. If the volume control and the inductive buttons are included at the same time, it will be difficult for patients to find the buttons for operation. Therefore, the advantages and disadvantages should be weighed in the selection: Generally, most severe and extremely severe patients can use inductors, while mild hearing loss can not use inductors.

3． Direct audio input

Direct audio input is especially useful in the following situations:
① The patient uses a wireless transmission system coupled with the hearing aid. The Adult and Children’s Department can greatly help from the wireless system. This function is especially suitable for hearing and speech rehabilitation training processes for deaf children, which can effectively improve the signal-to-noise ratio and speech intelligibility.
② The patient uses a portable directional microphone and is connected to the hearing aid through a wire. Generally, most people with severe or severe deafness use this device to increase the signal-to-noise ratio through wired input. At the same time, these microphones have better directivity than microphones worn on the head, and they are usually closer to the sound source, which effectively improves the signal-to-noise ratio and speech intelligibility. Patients watching TV in a noisy or reverberating environment, placing the microphone close to the sound source, or connecting the TV’s audio output to a hearing aid can also improve the signal-to-noise ratio and reduce reverberation.

4. Choose directional microphone or omnidirectional microphone

The use of directional microphones can improve the signal-to-noise ratio, effectively reduce the interference of low-frequency noise in the environment, and improve speech intelligibility. However, directional microphones are not suitable for all environments. Sex microphones have advantages.
Therefore, when placing orders for patients, we should try to consider selecting hearing aids that allow users to switch between omnidirectional and directional modes. If the patient wants the hearing aids (complete ear canal, ear canal) to be seen as little as possible, it is very difficult to install a directional microphone in these hearing aids due to the size limitation.
Directional microphones also have their disadvantages and inapplicability. For example, directional microphones are more sensitive to wind noise than omnidirectional microphones. In some cases, it is impossible to have the patient always face the sound source. Children need to hear the surrounding sounds, and generally use an omnidirectional microphone. And if the hearing aid wearer is not in the immediate range of the talker, even using a directional microphone may not provide any benefit.

5. Choice of multiple memory programs

Multi-memory program hearing aids allow users to use them in different environments. Users can choose appropriate listening programs according to different environmental sound changes, such as quiet programs, noisy programs, inductor programs, music programs, etc. With the continuous development of the intelligence of hearing aids, hearing aids that can automatically determine various sound environments and set appropriate hearing procedures in time will have wider applications.

6. Select hearing aid signal processing

The choice or change of multiple sound signal processing methods will play a vital role in the sound quality and actual effects experienced by hearing aid users. The choice of signal processing methods is more common in hearing aids with compression control. An example is given below.
(l) Compression limit mode and peak clipping control mode
In most cases, patients are accustomed to choosing the sound quality provided by the compression limitation method and the loud protection feature, but in some cases, patients will consider choosing the peak clipping control method. Compared with the compression limitation method, the large OSPL90 ‘peak-cut control method may produce a larger maximum output, especially the speech signal, which is very effective for severely deaf people.
Some patients who are accustomed to peak clipping control may not like the compression limit at first, but they also like this change after a period of adaptation.
(2) Wide dynamic range compression
We call those types of compression that use low compression thresholds as Wide Dynamic Range Compression (WDRC). Currently, wide dynamic range compression technology has been widely used in various hearing aids. No matter where the compression threshold is set, compared to linear amplification, most users who use WDRC can experience the obvious advantages of using WDRC in various environments. It turns out that WDRC technology is applicable to primary patients. But for patients with severe hearing loss, the compression threshold should be set relatively high, because they need a larger output.
(3) Multi-channel compression
Although some data from the poverty survey also show that patients with flat hearing loss tend to choose a single channel compression, as long as a suitable compression ratio is set, the selection of multichannel compression will not have a negative impact on most patients. Multi-channel compression technology can provide additional assistance for patients with moderate or severe hearing loss, because different degrees of compression can be used in each channel to provide more accurate compensation. For patients with a 2000Hz listening threshold exceeding 25dB above 500Hz, the most likely standard recommendation is to use multi-channel compression. In addition, the sub-channel processing can fine-tune the noise reduction function and feedback suppression
Features.
(4) Fast or slow compression
Multi-channel hearing aid users currently use fast compression, some use slow compression, and some combine fast and slow compression. For individuals, there is still a lot of debate on how to choose the right compression speed. There is no way to say which compression type is more suitable for a certain type of patient. Generally speaking, fast compression is more suitable for patients with relatively large changes in ambient sound intensity, and slow compression is more suitable for patients with relatively small changes in ambient sound intensity.
(5) Variable noise suppression
Patients who have a higher chance of using hearing aids in noisy environments tend to prefer amplification performance that automatically reduces gain in environments with poor signal-to-noise ratios. Using different amounts of compression and gain in each frequency range can potentially increase listening comfort and slightly improve speech intelligibility. Hearing aids with sophisticated speech / non-speech detectors on each channel are more comfortable than hearing aids that only respond to the overall input intensity.
(6) Feedback control
At the same time, its frequency and intensity are determined, and a conflict cancellation signal is automatically generated, thereby preventing acoustic feedback from occurring and not attenuating the effective gain.
② Automatic gain limitation. Specific to different hearing aids, there are generally two control methods: one is that once the acoustic feedback howling occurs, the hearing aid will immediately reduce the overall gain; the other is the notch method, which automatically determines the frequency of the howling sound and then Reduce the gain at this frequency to suppress feedback.