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Speech Understanding in Wind

Wind noise has been an ongoing issue since the beginning of hearing aid use. I remember 30 years ago talking to people about managing wind noise when they were wearing a body-worn hearing aid. I asked people to change the direction they were facing so their back was to the wind or stand sideways to the wind. I helped parents design headbands to be worn over the ear level hearing aids to protect the hearing aid on their child from wind exposure. I recommend that people wear baseball caps with material hanging down on the sides to reduce wind hitting a microphone. (Now we wear them to keep the sun off our face, reducing the risk of premature skin aging.)

For the industry as a whole, the focus has been on comfort and clarity of speech inside a house or gathering in a social setting. People wearing hearing aids can hear “indoors quiet” well but are struggling to hear speech during outdoor activities. The non-hearing aid wearer rarely complains of not hearing speech because the wind noise is too loud. Playing golf or watching an outdoor sports event can be frustrating while wearing hearing aids. Try playing outfield wearing hearing aids and your coach is yelling instructions to you. Why do hearing aids pick up so much wind noise?

First, we need to understand what happens to the microphones of a hearing aid when wind blows across it. The microphones are designed to pick up sound pressure changes but the poor things think that the phantom noise caused by vibrations of the microphone membrane is from sound pressure changes like speech. And more importantly, it does not need to be a significant wind to be picked up by the hearing aid. The microphone is picking up fluctuations in the air, meaning the wind distraction is neither a sound nor a noise. We know people will not wear hearing aids with big fluffy windscreens on them like TV crews use to protect their microphones! How does the industry create a hearing aid that reduces the air fluctuations while letting the desired sound in?

What has been used is a two-step process; detection of the low frequency interference that wind causes and suppression of this unwanted sound. To help suppress the sound, omnidirectional microphones are used. Some hearing aids automatically switch to omnidirectional when wind is detected by noticing the difference in input between the two microphones on each aid. But if you are outside with someone and having a conversation, this adjustment may make it difficult to focus on what is being said. If the hearing aid has enough frequency channels to detect wind as opposed to speech, it is able to attenuate those channels.

However, any time we take sound away, speech clarity is compromised. You don’t hear the distraction, but you can’t understand the words, either!

Comfort in wind is enhanced by the above scenario with the assistance of a new technology called binaural voice stream to help with clarity. This technology uses four microphones on two hearing aids to regulate the wind noise, operating under the assumption that wind is often picked up by a single microphone or both microphones on the same hearing aid. Another way to say this is that wind usually comes from one side of your body more than the other. The desired speech sound is picked up by all the microphones. This technology takes the speech signal from the hearing aid with the least amount of wind distraction and streams it to the opposite hearing aid. This hearing aid then exchanges its low frequencies with the other hearing aid because the low frequency sounds are most likely to be contaminated by the wind. The high frequencies are not exchanged to help maintain the ability to localize the sound source. You as the user do not have to do anything; the computers inside the aids are doing all the work at lightning speeds.

All technology is available for you to try at little or no cost. A previous negative experience with hearing aids is no longer a reason to put off experimenting again. Your quality of life in and out of the house is what we as audiologists are attempting to enhance. Grow your life into what you want; don’t let your life compress because of hearing issues. The most common comment I hear from my patients is that I changed their life! I truly believe I have the best job in the world! FBN

By Dr. Karon Lynn, Au.D

Trinity Hearing Center is located at 1330 N. Rim Dr., Suite B in Flagstaff. For more information, visit the website at TrinityHearing.net. Karon Lynn is a doctor of audiology with 30 years of experience working with hearing impaired individuals. Dr. Lynn may be reached at 928-522-0500 or at audio@trinityhearing.net.

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