How They Work?
The technical principle of all hearing aids is very similar.
The microphone(s) catches the sound which is converted to a digital signal. A Digital Sound Processor (DSP) modifies the signal to compensate for hearing deficiencies. A loudspeaker transmits the signal to the ear.
Hearing aid technology can be roughly divided into 4 main groups. To restore audibility, to suppress noise and enhance speech, to eliminate feedback and finally, convenience options.
Hearing Aid Features
Digital Sound Processor
Almost all hearing aids today are equipped with a digital sound processor which can be programmed to suit many different hearing loss configurations and can perform small miracles of signal processing all geared to help you hear better.
Modern digital hearing aids split the signal into a number of frequency channels to apply signal correction (amplification) and compression based on the audiogram configuration. The more channels a hearing aid has the more sophisticated and detailed its sound processing can be.
The number of channels necessary for a given prescription depends on the audiogram configuration. The steeper or uneven the hearing loss curve the more channels are necessary.
Hearing aids compensate for the measured degree of hearing loss by amplifying sound of a specific frequency area accordingly at a ratio to the loss.
Typically, initial compensation is not one to one to the measured hearing loss, but set according to special algorithms by the fitting software. Gradually as the patient’s auditory system gets used to hearing more sounds again the amplification is increased.
Compression means that the hearing aid software applies different amplification based on the intensity of the input signal. Soft sounds are amplified more and loud sounds are amplified less This is done, to compensate for your loss of dynamic range.
Noise Management Systems and Technologies
A large amount of Hearing aid computing capacity is dedicated to filter out noise from the acoustic environment and to enhance speech.
Modern hearing aid microphones can suppress signals from certain directions. Normally this technology is applied to suppress signals from the back or sides if identified as interfering with speech coming from the front. .
This technology limits the amount of information the hearing aid sends to the brain and thus making language comprehension easier.
Because of your hearing loss, you gradually hear less and less of all the sounds (noise) which surround us wherever we are. Because of this, your auditory system might not be able to accept noise at the same loudness level as speech.
One of the most important functions of modern hearing aids is to reduce the amount of background noise to a level where it is acceptable for you to use your hearing aids comfortable.
Due to the proximity of microphone and speaker in a hearing aid, they are prone to cause feedback (an annoying whistling sound) if they are too loud in certain frequency areas, not fitted well into the ear, are being touched etc. Feedback suppression technology helps to reduce this annoying problem.
Channels – depending on the software the DSP breaks down the incoming signal typically into 4 – 16 channels. Overall signal and feature processing quality & flexibility depend then on this number of channels.
Multi microphone performance – by measuring the different signals which arrive at different microphones separated tiny time differences the DSP can ignore signals or signal parts from certain directions. This technology improves speech in noise.
Noise management – software on the DSP measures the content of signal and noise in each channel and accordingly filters out or applies less amplification where noise is present.
Feedback management – by measuring the amount of feedback present, the DSP can effectively apply phase cancellation and remove it instantaneously. This is not just convenient but also very important for sound quality
Modern chip design makes your hearing aids high tech communication devices which can communicate with each other (left with right) and with all your Bluetooth enabled devices.
Wireless in a hearing aid can mean many things
Wireless Programming - While your fitter adjusts the parameters in your hearing aid they are not connected via a wire to the computer but communication happens over a wireless technology.
Compatibility with wireless - Transmitters enables your hearing aid to connect wirelessly to your favorite audio device, TV, phone, etc.
The Hearing aid on your left ear can communicate with the Hearing aid on your right ear. So if you change volume or another function on one side it will happen automatically on the other.
Binaural Telephone Mode
Is a special sub-feature of Binaural communication. If you hold your telephone close to one of your hearing aids, it will communicate this to the hearing aid on your other side and change the settings based on your previous defined preference in such a situation.
Binaural Spatial Mapping
Currently the most sophisticated hearing aid function. Hearing aids on both of your ears are constantly in contact with each other and adjust signal processing based on what signal arrives on the other side. Just as the brain does if you hear well. This feature helps with hearing in noise and other challenging environments.