When we talk to people about their hearing and what situations they most want to hear better in, for most people their top priority is to have an improved ability to hear in noisy environments. You’ll know that hearing aids are getting smarter, but do you understand what clever things the hearing instruments do, without you knowing, to deliver great hearing in noise?
You may be surprised to know it’s all about directional microphones.
Now, let’s be clear about this. There are only two main suppliers of microphones in the world. This means that every hearing aid manufacturer has access to exactly the same directional microphones in their hearing aids.
And, when we say that the hearing aid microphones are directional, this isn’t strictly speaking true. The microphones are omni-directional, which means that they pick up information from every direction. But, when you have two microphones lined up a fixed distance apart, a very clever (and fast!) computer can use timing differences to determine what is ahead and what is behind the hearing aid wearer, and can thus perform in a directional (beam-forming) manner.
If you’d like the technical version of this very brief explanation, you should read this article: https://www.audiologyonline.com/articles/providing-some-direction-beamformers-explained-26260
If all the microphones are the same, you’re probably asking yourself what differentiates the hearing aids of two hearing instrument manufacturers? Or two levels of hearing aid technology from the same manufacturer?
The point of difference is the performance of the computers driving the hearing aids, in other words, the hardware and software. The hardware (the power of the computer chip) determines the working memory and speed at which the hearing instrument can perform its calculations. The software is the algorithms (calculation) which the computer has been programmed to perform to enhance sound and, ultimately, speech.
An analogy might be giving 10 teenagers exactly the same BMX bike and observing what tricks they can complete on it. Some of the teenagers will be stronger and fitter than the others (say, the hardware), so can push the bike to limits that the other teenagers cannot. Others in the group will have better skills, perhaps because they are more experienced, daring or determined (say, the software). So all kids have the same starting point (the bike), but the kids who have both the strongest bodies and best skills will be the ones who perform the best.
To reiterate, the performance of the directional microphones is determined by the hardware and software of the computer chip analysing the information from the microphones.
This is all very well, but what does this mean for you? Let’s explain the directionality feature first.
When you wear a hearing instrument it is constantly sampling the environment to determine what kind of situation you are in. Are you listening to the TV in a quiet room? Are you walking in the wind? Are you in a café?
A hearing aid that can accurately identify and classify your environment will be able to deliver you just the right kind of sound for each different situation. And this is where directional microphones come into their own. Natural human behaviour in a difficult listening situation is to face the person, or the sound, that you are wishing to hear. If you are listening to speech when there are other sounds around you, you will hear better if the hearing aids automatically form a beam to cover the speech that falls in front of you, and cancel the sounds that come from the side, and from behind you.
Most hearing aids can automatically form a 120 degree beam. But some of the smarter instruments can use a wireless connection and take the information from two microphones on one ear and the two microphones on the other ear and process it together to form a 90 degree beam. The narrower the beam, the less noise you will hear from the sides, and the better you will hear the sounds in front of you!
Some of the very latest hearing aids also have motion sensors in them, so they can analyse both the auditory inputs, along with any movement of the hearing aid wearer (just imagine how powerful that computer chip is!). These instruments have the added ability to decide against forming a beam while you are walking – when you are walking it’s nicer to hear the person beside you, and safer if you can hear what’s behind you!
There are some considerations in terms of where you position yourself within a noisy environment to get the best possible hearing. Read here to find out more.