How do digital hearing aids work?
The most basic function of a hearing aid is to amplify sound. Digital hearing aids, which have only been around since late 1990’s, do this in a rather sophisticated way. From a technical perspective, the reason modern technology offers such a natural and rich sound, is largely due to there fact that they are much better able to match a wearer’s unique pattern of hearing loss.
Older hearing devices only amplified hearing in two channels – high-pitched sounds (treble) and low-pitched sounds (base). Modern hearing aids separate sound into numerous frequency bands and amplify each band by the amount required to restore normal hearing levels.
As sound enters the device, it is broken into multiple frequency bands. Each band is then amplified by the amount necessary to return the wearer’s hearing to normal levels at that band. With digital technology, devices can now break sound into as many as 48 different bands.
Historically, the whistling sound (feedback) that many hearing aid users encountered was both uncomfortable and embarrassing. This was caused when the hearing aid’s microphone picked up amplified sound. Sound travels in waves. The digital hearing aid can now detect the frequency of the wave shape that is causing the feedback and counteract it within fractions of a second. So, there will be no annoying and embarrassing whistling from your hearing aid.
Improvements in feedback management have allowed hearing aid manufacturers to develop devices that do not obstruct the natural passage of sound through the ear canal. Previously, wearers of hearing aids would complain of a “talking in a barrel” sensation, like you can experience when using your fingers to block your ears and listening to the sound of your own voice.
Open fit hearing aids have very thin tubes that enter the ear canal and smaller cases that rest behind the ear, making them barely visible.
Additionally, hearing aids that sit within the ear canal can now have greater ventilation. The end result is far more comfort and clarity for the hearing aid wearer of today.
One of the problems with older hearing aids was that they amplified all sounds equally – whether the source of the sound is the person who the wearer is listening to, or background noises, such as traffic, air conditioners, or ambient noise from a crowded room. This led to discomfort and did not help the user to follow conversations in difficult environments.
Now digital hearing aids can actually tell the difference between speech and background noise and do this individually for every frequency band. The hearing aid then amplifies the speech sounds and reduces the amplification of background noise.
Now consider the size of a hearing aid and the number of computations that it must perform every few milliseconds across up to 48 frequency bands and then deliver the enhanced sound into the ear canal. The mind begins to boggle! It may be easier to simply enjoy the results of noise management – greater listening comfort and clarity.
Most people with hearing loss find that trying to follow a conversation in a noisy place can be a tremendous struggle. Logically, most conversations are with people who we are facing, while distracting background noise will come from the sides and behind us.
A modern digital hearing aid can actually pinpoint the location of sounds. It does this by using more than one microphone and gauging the difference in time that it takes sounds to reach each microphone – even though the microphones are only a few millimetres apart!
It will then provide the greatest amplification to sounds coming from in front of the wearer and less amplification to sound coming from the sides and behind. Directional microphones can be extremely beneficial in difficult situations like restaurants and are the greatest factor in improving a wearer’s ability to follow conversations in noisy places.
Different listening environments often call for different settings within hearing aids in order to maximise their effectiveness. For example, when listening to music, the user would prefer to turn off features that may misinterpret elements of the music as noise. When in a quiet room, a wearer will not need the benefit directional microphones and noise reduction to the same extent they would in a crowd at the football.
Advanced hearing aids allow the user to change the settings by pressing a small button on the device. The most advanced hearing aids will even listen to the environment and change the hearing aids settings automatically, without the wearer needing to touch or think about their hearing aids.
Wearers are increasingly looking for solutions to improve their ability to use their hearing aids more effectively in partnership with their mobile phones, digital radio, plasma televisions and personal stereos (e.g. Smart Phones, iPads, Tablets).
In response, manufacturers have developed streamers that connect wireless devices to the user’s hearing aid. The benefit is that this delivers improved performance in terms of speech intelligibility and sound quality as signals from the external devices are streamed directly into the hearing aid, without background noise and the need for the hearing aid to first process a sound signal.
Smart Phones now performing the task or wireless streamers
Up until 2014, someone wanting to connect their hearing aids wireless to their phone, tablet or music player would have been required to purchase an optional wireless streamer with their hearing aids. Now, since the launch of the ground-breaking ReSound LiNX, it is possible to have your smartphone (iPhone) manage these tasks. So wearers can manage streaming and functions such as volume and program settings from an easy to use App on their phone or iPad.