The inner diameter and outer diameter of the sound guide tube is one of the main factors affecting the sound propagation.

Inner diameter effect: Changing the inner diameter of the sound tube will affect the high-frequency response of the hearing aid. Generally speaking, the smaller the inner diameter of the sound guide tube, the higher the low-frequency gain and the lower the high-frequency gain.

Outer diameter effect: The outer diameter mainly determines the thickness of the sound guide tube. The larger the outer diameter, the thicker the sound guide tube.

Because the thick sound guide tube can attenuate the sound to a certain extent, when the sound leaks during the propagation process (usually occurs at the coupling of the sound guide tube and the ear hook), the larger outer diameter can be selected The sound guide tube can attenuate the leaked sound to a certain extent, reducing the possibility of howling.

The following table shows #13 sound guide tubes with different outer diameter and inner diameter. As seen in the table, the thickened sound tube can attenuate the sound by about 2 dB compared to the standard sound tube. Generally speaking, the sound guide tube with thick wall can be used for high-power BTE hearing aids.

Hearing aid selection is a very complicated process. In the actual selection process of hearing aids, in addition to choosing the right hearing aid, the fitting technician should pay more attention to the details and choose the sound tube type reasonably, so as to ensure the sound quality and effectively achieve "precise fitting".

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