Today’s hearing aids incorporate a slew of technologies to overcome the limitations of yesterdays hearing aids. There are literally hundreds of different types of technologies and manufacturers love to come up with their own fancy names for them. You don’t need to understand all of the technologies used by your hearing aid to benefit from them, but for those who are interested, some popular technologies are explained below.
Compression refers to a hearing aid’s ability to amplify incoming sounds differently, depending on their incoming volume. Soft sounds are amplified a lot, moderately loud sounds are amplified less, and loud sounds are amplified even less (or not at all). Multichannel compression not only analyzes the loudness of the incoming sounds, but also the frequency or pitch. This prevents the hearing aid from over-reacting in complex situations. For example, in a restaurant situation, the hearing aid can suppress the loud, high frequency silverware clatter, without being forced to supress lower frequency speech sounds as well.
An omnidirectional microphone picks up sounds from all around the listener. A directional microphone takes into account the direction the listener is facing, usually emphasizing what’s in front. A directional microphone is particularly helpful when trying to listen to speech in a noisy environment.
Some hearing aids have a button that changes between multiple programs when pressed. While many hearing aids adjust automatically to different types of sounds and listening situations, sometimes a specific program for a specific situation is nice to have. It’s like having a pocket full of hearing aids, with each one programmed for a specific situation.
Hearing aid wearers typically don’t want to hearing EVERYTHING. Some sounds are simply unwanted noise. Hearing aids are becoming better at identifying which sounds are welcome, and suppressing the unwelcome ones. Noise reduction algorithms analyze the incoming sound, and if it doesn’t look like speech, the hearing aid doesn’t amplify it as much as it normally would.
Most people are familiar with the “whistle” of a hearing aid. Whistling is the sound the hearing aid makes when some of the sound that should be going into the ear canal bleeds out and becomes re-amplified, over and over. Feedback cancellation looks for that familiar sound, and if it’s discovered, it introduces an extra (out of phase) sound that collides with the feedback tone, and cancels it out.
A telecoil is essentially a radio antenna built into the hearing aid. It’s most commonly used to pick up electromagnetic signals from the speaker magnet inside a telephone. The microphone turns off, and the listener hears only the telephone signal. Telecoils can also be used to communicate with other devices, such as environmental loop systems or hands-free communication devices.
Some hearing aids can now syncronize with Bluetooth-enabled devices. Unfortunately, you can’t fit a bluetooth antenna into a hearing aid (yet), so a separate transmitter is required. The most common use of bluetooth is to communicate with a cell phone. The sound goes directly into your hearing aid, and your voice is picked up by a microphone built into the transmitter.