Why do my hearing aids whistle?
Many hearing aid users wonder about that high pitched whistle sound that sometimes comes from one or both of their hearing aids. What is it and why does it happen? That high pitched sound is referred to as feedback and it can occur with any sound system that involves a microphone and a speaker, just like a hearing aid.
How does feedback occur?
In order to understand feedback, we will first look at how a hearing aid works. All hearing aids have at least one microphone which picks up sound waves from the environment and converts them to an analog signal. The analog signal is converted to a digital signal, which can be amplified and manipulated by the hearing aid to fit the user’s needs. After processing, the signal is converted back to an analog signal and sent to the receiver (speaker). The receiver converts the analog signal back to an acoustic signal and delivers it to the ear as sound. The sound travels down the ear canal and is absorbed by the ear drum.
Sometimes, excess amplified sound leaks from the receiver and gets picked up again by the microphone of the hearing aid. The microphone will re-amplify the already processed sound and the signal gets stuck in an endless loop of being delivered by the receiver and picked up again by the microphone. This creates that loud, high- pitched squeal we refer to as feedback.
How can I reduce feedback?
Feedback is possible with any sound system, and you have likely heard it occur at some point with a speaking microphone or a band setting up to play. While occasional feedback is normal, excessive feedback is not. Let’s look at some ways that feedback can be reduced.
- A good fit- A well fit hearing aid will minimize how much sound can leak out of the ear canal and get picked up again by the microphones. This is especially important for custom “in-the-ear” hearing aids. Behind-the-ear products have the advantage of more distance between the microphones and the receiver, which helps to reduce feedback. Keep in mind that it is normal for your hearing aids to whistle while you work to get them in your ears properly because a good seal has not yet been formed.
- Turn down the volume – When your hearing aids are turned up all the way, the output from the receivers is greater than it is at lower volumes. This increases the risk of the microphones picking up the excess sound. If you consistently need to turn your hearing aids up to their maximum level and this is causing excessive feedback, it may be time to speak to your audiologist regarding a more powerful hearing aid or a different fit.
- Clean your ears- Wax build-up in your ears can cause significant feedback because the sound is reflected by the wax instead of absorbed by the ear drum. Typically, hearing aid users will describe a situation where feedback was not present and then came on suddenly, in all situations and in only one ear. Consider having a doctor look in your ears for wax if you think this might be your problem.
- Clean your hearing aid – To the same point, wax build up in your hearing aid can also cause significant feedback if it blocks the sound from escaping from the receiver. Check to see if the receiver is clogged with wax and then refer to the proper way to clean that wax depending on your style of hearing aid.
- Feedback manager- Most hearing aids have feedback managers available in them, and many are very successful at reducing excessive squeal. Your audiologist can activate this feature on your hearing aids if it is available.
Keep in mind that in certain situations, all hearing aids will give off feedback. For example, if you take your hearing aid out of your ear and cup your hand around it, it should squeak. In fact, if you do not hear it squeak in this situation, it is possible that your hearing aid is not working correctly. As mentioned previously, it is also normal for hearing aids to feedback while being put in and adjusted to sit properly. Even after the hearing aids are in correctly, feedback can still be induced by covering your ears with your hands or putting something like a headphone over the hearing aids.
If feedback is a concern or you feel your hearing aids squeak excessively, talk to your audiologist about some ways to troubleshoot this problem without sacrificing your listening experience.