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Directionality
(This is the only proven feature on a hearing aid, shown to improve speech understanding in noise)
Omni Directional
Directional microphone modes:
Fixed Directional
Adaptive Directional
Multiband Adaptive directional
Wireless Beam forming or Super Directionality
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Directionality is a hearing aid's ability to separate the speech you want to listen to from the background noise speech that you are not listening to. Digital hearing aids are very smart and can identify speech versus noise but they cannot tell which person you are actively listening to. It is however generally safe to assume that you will be looking at the person you are speaking to and the hearing aids can adaptively change their direction of most sound pick-up based on this assumption.
When a hearing aid finds itself in quiet or with only a single person speaking in the room, the hearing aid will be in omni-directional mode where everything around you is picked up equally loud. Very small in the ear hearing aids often only have an omni-directional microphone.
When a hearing aid finds that there is speech present in the presence of background noise, it will switch to directional microphone mode. When this happens sounds in front of you will be picked up louder than sounds next to or behind you.
The most basic directional microphone is a fixed directional microphone, which keeps sounds right next to you at a minimum, speech in front at a maximum and those sounds behind you a little softer than those in front of you.
An improvement on the fixed directional microphone is an adaptive directional microphone. This microphone system consists of two omni-directional microphones, electronically linked and controlled which, still keeps the speech in front of you at a maximum, but finds the single loudest noise anywhere next to or behind you and keeps it softer than the sounds in front of you. This was first made possible in around 2001 with the advent of second generation digital hearing aids.
The most flexible microphone systems are multiband adaptive directional microphones. The more bands the microphones have the more noises it can track and keep softer. So you can have multiple noise sources suppressed behind the hearing aid user. (introduced around 2004-2005)
There is only one such system available on the Australian market today and it is made by Phonak . This system uses two microphones from each hearing aid (left and right) and wirelessly combines the signal from all four microphones to give a very narrow pickup from directly in front of the hearing aid user. Introduced in October 2010.
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Better hearing and understanding of speech in a variety of situations especially in background noise.
Omni-directionality allows you to hear people all around you, so you can hear them speaking clearly even behind you.
For hearing and understanding speech better when you are in noise as long as the noise is predominantly behind you.
This gives you slightly better hearing in noise than without the hearing aids.
This is a more flexible system for hearing in noise and allows slightly better hearing in noise than provided by a fixed directional system as the loudest noise can be anywhere behind you, not just next to you as with a fixed directional microphone.
This is a far more flexible and capable system than adaptive directional microphone systems. More bands suggest better hearing in noise.
Super Directionality is still in its first generation, but for the first time it allows the hearing aid user to be able to better understand speech in a noisy cocktail party like situation, where noise is all around them.
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Noise Reduction
Bands
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Noise reduction is the hearing aid's ability to automatically reduce non-speech background noise like traffic, fans, machinery relative to speech.
Noise reduction is performed in a number of bands or channels. The hearing aid breaks up the sound entering the hearing aid into a number of slices (bands/channels. Each slice is analysed in real time to see whether it contains speech or noise or a combination of speech and noise.
If a band/channel contains only noise then the volume is reduced for that particular slice (band). If it contains only speech, that slice might be raised in some hearing aids using speech enhancement. If a band contains both speech and noise it is generally left alone as the hearing aid does not want to reduce speech.
The more bands a hearing aid has, the better the resolution it has and the less likely it is that speech and noise will both occur in a single band or channel. So the hearing aid is better able to separate speech from noise with more bands.
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This helps make the hearing aids more comfortable while wearing them in noise.
More noise reduction bands leads to better comfort in noise. Note this feature has not been shown to improve hearing in noise by much at all.
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Feedback Manager
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Most modern digital hearing aids have some way of combatting whistling in the hearing aid. The best current way of stopping the hearing aids from whistling is called phase cancellation. This means that the hearing aid can recognize when it is whistling and put out an exactly opposite sound which effectively stops the whistling. Some hearing aids are better at this than others, but they are all a lot better at stopping whistling than it used to be. Most modern hearing aids have this feature but some brands are much better at this than others.
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This allows the hearing aid to be much more comfortable in your ear as it does not need to be as tight anymore to stop whistling.
It also allows us to fit hearing aids which leave the ear canal completely open, which is what it needed for addressing high frequency hearing loss successfully.
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Channels
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Channels allow the hearing aid fitter to adjust the volume of the hearing aid in each slice of sound to best match you hearing loss. Clinically about 6 channels are sufficient to match any hearing loss out there. There are some claims that more channels mean better sound quality, but there exists very little evidence for this. Most hearing aids' channels match their noise reduction bands and have more importance for noise reduction than added flexibility. Clients do anecdotally report that more processing channels sound more natural, but this has not been proven. You also need to consider that the human inner ear has about 22 bands of which about 20 are usable within the frequency range hearing aids use, so any more than this is irrelevant and may cause distortion.
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Channels give you flexibility to have the hearing aid accurately adjusted to your hearing loss.
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Telecoil
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A telecoil or t-coil is a specialised and relatively large bit of electronics inside some hearing aids, allowing the sound from a phone or loop system (churches/theaters) to be heard directly in your ears without distance or background noise being an issue. It is often more useful for people with larger degrees of hearing loss. It also takes up quite a bit of space in the hearing aid and as such is only found in larger hearing aids.
A manual telecoil requires the user to press a button or flick a switch on the hearing aid or its remote control (if available) to turn the telecoil on.
An autophone/easyphone is a telecoil that automatically activates when an appropriate phone is brought close to the hearing aid, triggering magnetic switch.
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A telecoil gives people with more severe hearing loss better access to using telephone and public address systems as long as there is a hearing loop available in the room.
This leads to easier phone use while wearing the hearing aid, if you have an appropriate phone and your hearing loss is great enough.
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Programs
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Hearing aid programs are a collection of hearing aid settings each designed for specific hearing situations. These can be either selected automatically if the hearing aid is sufficiently advanced or by the user in more basic hearing aids.
A great number of hearing aids today have a number of automatic programs that the hearing aid can select from, depending on which situation it determines you to be in. Usually the situations a hearing aid can automatically determine could include speech in quiet, speech in noise, noise only and music. The less advanced the hearing aid the fewer situations it can automatically identify.
There could be a very small selection of situations where you might find the automatic to be less than optimal. In these few cases an extra set of settings could be put in a spare manual program slots, allowing you to select that program when this unusual situation is encountered. Some less advanced hearing aids only have manually selectable programs. Manual programs are usually selected by pressing a button on the hearing aid or by pressing a` button on a hearing aid remote control, when available.
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Programs offer you flexibility to give you more acceptable hearing in a variety of listening situations.
Automatically switching programs mean better hearing in more situations without you having to think or do anything about it. This means more convenient hearing.
This means more flexibility should you need it.
Hearing aids with automatic programs gets the setting right about 90% of the time, while people who have to manually change programs get things right between 17% and 30% of the time.
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