Limitations of hearing aids and implants


Before going further, it’s important to understand some of the limitations of hearing aids and implants which may prevent them reproducing heart and lung sounds accurately. Hearing aids and implants are designed mainly to help us hear speech and pick it out from background noise. So programmes usually enhance speech frequencies, not the low frequencies we need to hear for ausculation. Even if we can set up a dedicated stethoscope programme to mitigate this [1], there are other limitations.

Hearing aid speakers don’t have a good response at the lowest frequencies. So heart and lung sounds may be attenuated (quieter) and the very lowest frequencies may not be reproduced at all. Which means that if you are relying on your hearing aids’ speakers, it’s possible you will miss some diagnostic sounds. Implants may also cut off above the low frequencies we need to hear [2].

So although we can connect some stethoscopes to hearing aids using the T setting (induction), direct audio input or even FM or Bluetooth systems, it’s preferable to deliver the sound direct to your ears. Use hearing aids with either vents or open fitting or take them out. Use a stethoscope with either headphones or normal or adapted ear pieces. This allows sound to travel directly from the stethoscope, though the vents or open fit domes to your ears, independently of your hearing aids. If you are using headphones, make sure they have a good low frequency response.

If you don’t have vents or open fitting, ask your audiologist if your moulds can be adjusted. But some of us will have feedback problems with vents.

And you can mitigate these issues by choosing a stethoscope with visual display.

You’ve clarified whether or not you need amplification. You understand the limitations of hearing aids and implants. Your options now depend on what sort of hearing aids or implant you use.


[1] A dedicated stethoscope programme can filter out the higher frequencies that would otherwise be amplified by your hearing aids/implants and obscure the heart and lung sounds. The programme can also boost the lower frequencies. Cardionics advises “increasing the gain of low frequency improves heart sounds … [and you] will need to disable automatic noise reduction.” But remember that this won’t include the very lowest frequencies.

[2] See Cardionics Technical Information Bulletin E-7710 and Technical Considerations in Using Stethoscopes. BAHAs may be limited by the processor. Cochlear implants can be limited by both software and hardware issues. Some are better than others.

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