What is the difference between channels and bands?

WHAT ARE HEARING AID CHANNELS & BANDS
Consider a condition where we split up the audio spectrum we generally hear into discrete sections or slices (hopefully if the aid does its’ job properly). These are what are customarily referred to as “Channels”. Within each of these channels, based upon the device, there are one or more adjustments for the amplitude, response and/or other parameters of the very specific audio frequencies that fall within the range of this specific channel or section of the audio spectrum.
Adjustments of the “bands” within each of these discrete slices or sections of the audio spectrum generally consist of amplitude of the amplification at 4 or 5 levels that can, in effect, compress or expand sounds to different volume levels and other aspects with respect to their initial level coming into the microphones of the aids.
In the Exelia Arts I normally wear, there are 20 of these Channels that start at 140 Hz and end at 9.5 kHz. Each of these “channels” allows adjustment of the frequencies “bands” with those 20 discrete channels as follows:

1. Very Loud (MPO)
2. Overall Gain
3. Loud (G80)
4. Medium Loud (G60)
5. Soft (G40)
6. Very Soft (TK)
7. Global Compression
8. Sound Recover
   You can see there are a lot of “nobs” to tweak to endlessly set the sound to what you like – or get rid of what you don’t like. I personally like the “wife notch” setting that can take a wife’s voice down about -90db! I’m working on a sound substitute/relocate function that substitutes her voice spectrum for Demi Moore’s voice spectrum. (Just kidding dear).
   If you are a self-programmer or if your audiologist can spend endless hours experimenting with you, it can be rewarding. To learn more about this, here is an interesting page:
   [SIZE=3]http://www.mlprestwich.com/hearingaid-information/[/SIZE]29 and
   [SIZE=3]http://www.mlprestwich.com/hear/[/SIZE]27
   If you want to “tweak” test these elements for yourself and have a PC, download iPFG 2.6b (free) install the program and run the program with a dummy test client – no aids needed, no programmer needed to make a test fitting to see the elements above for yourself. Just create a dummy client and select any set of Phonak aids to see what they do. Or, import this fitting below into iPFG for a demo of the above aspects without having to load your own client/aids. From: [SIZE=3]http://www.mlprestwich.com/10HA/FAQ/[/SIZE]13 Just click on and download
   MikeExeliaFitting10242011.ipfg and save to your local hard drive, then import into iPFG. Public domain information – no privacy issues.
   [SIZE=3]http://www.phonakpro.com/com/b2b/en/professional_tools/fitting_equipment/software/downloads.html[/SIZE]14
   This next section is taken from [SIZE=3]http://hearingaidinsider.com/articles/hearing-aid-technology-and-features[/SIZE]12
   “Channels and Bands
   There is a lot of confusion in the hearing aid industry relating to channels and bands. Simply put, channels affect how the hearing aid operates; bands affect how the hearing aid is adjusted. In general, having more channels is better than having more bands, and the more channels the better – to a point! Research has shown that more than eight channels offers marginal improvement. More important than the actual number of channels or bands is what the hearing aid is doing with them. In other words, don’t place too much emphasis on these numbers. The more noise you regularly experience, the more you will benefit from a greater number of channels and bands.
   Channels are sections or slices of the frequency spectrum that are processed more or less independently by the hearing aid. For example, if a hearing aid has eight channels, it will divide up the sound into eight separate sections and each section can be processed independently from the other seven. This is useful for automatically adjusting to a variety of sound environments. Usually the audiologist or hearing specialist can make some changes to the channels for the management of loud sounds.
   Bands are used to adjust the hearing aid’s amplification characteristics and for fine-tuning the hearing aid to the wearer’s loss and preferences. Hearing aids can have a band for each channel or multiple bands per channel. Like channels, the audiologist or hearing specialist can adjust these bands to the wearer’s preference.”
   -forrest

@ZCT said:

<SNIP>
All that said, you probably want at least four channels. But don’t fall into the trap of assuming that if it has 20 channels it must be a better sound quality. This is not necessarily true.

What you should be concerned about is whether your hearing professional can demonstrate good hearing to you by means of letting you listen to some real digital hearing aids.

The bold statement is true but, unfortunately, the HA manufacturers only put the more advanced features on aids with more channels. The channels may not give the sound improvement, but the advanced features surely may.

@iceman0486 said:

In essence the channels give us (specialists/audis) points at which we can manipulate the levels of sound. (A little self promotion) For example, the Liberty SIE64 is a hearing aid with 64 channels - many users have noticed a clearer and more “crisp” sound, especially in background noise when compared to other hearing aids.

I’ve never fitted a hearing aid with 64 channels before. However, I am professionally curious as to why they would go with so many channels.

A really thorough hearing test provides ten results from 250Hz to 8000Hz. Testing higher than 8KHz has not been proven to be useful in adults. And below 250Hz often produces a false reading thanks to vibrotactile response. Most audiometers are only capable of half octave frequency selection, not quarter octaves (or more).

So given this reality of audiometry, I was wondering if you could explain the scientific benefit of 64 channels, versus let’s say 32? I mean are you not essentially guessing where a patient’s results might fall given that no hearing test actually tests 64 frequencies?

It just seems to me that the processor could be doing something else more useful with its time than try and deal with 64 channels. But maybe you have some information I don’t, since I don’t think I’ve ever fitted more than 20 channels on a hearing aid in my career.

@ZCT said:

I’ve never fitted a hearing aid with 64 channels before. However, I am professionally curious as to why they would go with so many channels.

A really thorough hearing test provides ten results from 250Hz to 8000Hz. Testing higher than 8KHz has not been proven to be useful in adults. And below 250Hz often produces a false reading thanks to vibrotactile response. Most audiometers are only capable of half octave frequency selection, not quarter octaves (or more).

So given this reality of audiometry, I was wondering if you could explain the scientific benefit of 64 channels, versus let’s say 32? I mean are you not essentially guessing where a patient’s results might fall given that no hearing test actually tests 64 frequencies?

It just seems to me that the processor could be doing something else more useful with its time than try and deal with 64 channels. But maybe you have some information I don’t, since I don’t think I’ve ever fitted more than 20 channels on a hearing aid in my career.

For the most part, I agree on the idea of freeing up the processor to work on other things. However all of our aids are at least 32 channel devices. To quote our wonderfully vague manual "ADRO uses statistical analysis to optimize the signal at the hearing aid output in every frequency channel independently. The hearing aid output adapts to any listening environment.
<O:p</O:p
The math on the programming seems to make sense and experienced HA users tell me there is an improvement in the clarity of sound. But as I mentioned before, I feel like we are missing out on a number of features that make the hearing aids themselves more convenient to use - like auto-telecoil and wireless synch. Still, at $3,000 a pair I feel like it is a good deal.

Iceman: In my opinion 64/32 channels is nonsence. Simply designed to sell more aids to the typically uninformed HOH.

And what pro has time to individually set 64 or 32 channels.

There is a theory that the area between channels phase shifts cause some small amounts of distortion.

Again dishonest promotion and hoke.

It’s bad enough when top manufacturers push 20 mostly useless channels.

I note that a few marginal mfg’s promote bands as channels…this is not really honest. Ed

@Research said:

It would be most appropriate to consider a hearing aid band as the ‘gain’ handle that appears in the programming software. The more bands you have available, the more accurately the hearing aid response can be shaped to a hearing loss. A hearing aid channel is the frequency division in which signal processing processing is done. This means that compression, feedback cancellation and digital noise reduction are done within channels.

wrote something similar here.
http://www.hearingaidforums.com/showpost.php?p=44442&postcount=410

in addition more channels make sounds sound better but does not help when it comes to speech in noise. counter intuitive but it’s true.

@ed121 said:

Iceman: In my opinion 64/32 channels is nonsence. Simply designed to sell more aids to the typically uninformed HOH.

I remember when america hears came out with their aids and made the 64 channel claim. We were all like, “what manner of sorcery is this?” I believe it was then that we realized that the manufacturers and us were using bands and channels interchangeably. I believe it was sometime after that people on the forums and in the industry started making definite distinctions between bands and channels and america hears 64 channel claim mysteriously disappeared from their website.

@ed121 said:

Iceman: In my opinion 64/32 channels is nonsence. Simply designed to sell more aids to the typically uninformed HOH.

And what pro has time to individually set 64 or 32 channels.

There is a theory that the area between channels phase shifts cause some small amounts of distortion.

Again dishonest promotion and hoke.

It’s bad enough when top manufacturers push 20 mostly useless channels.

I note that a few marginal mfg’s promote bands as channels…this is not really honest. Ed

I didn’t want to be so harsh as to say this and dis what another professional was dispensing, but I completely agree.

I’ve never seen any credible study that demonstrates any meaningful benefit of so many channels. I agree with crossover issues. And of course when you are fitting more frequencies than you even tested, you are basically taking a guess. And the more of these guesses you take, the bigger the chance of guessing wrong.

Finally, the more channels you have the more you are directing the chip to think about each channel and less on more useful stuff such as advanced background noise suppression, advanced feedback suppression, etc.

@EnglishDispenser said:

[tired sigh]

This has been discussed many, many times before here.

The typical human ear will be happy with say a 6 channel/band hearing aid.

However the 20+ band hearing aids use the extra bands for … advanced noise reduction … NOT hearing correction.

Yes but conversely you have to consider that few companies offer a top of the line six channel hearing aid.

So while you may claim that six channels is enough (which I happen to disagree with BTW), you are going miss out on a lot of other features that could help a patient do well in more challenging situations.

Of course, there is an obvious and quantifiable law of diminishing returns here, and getting up to 64 channels+ is clearly way past the bar. Unless there is some new science out there that I am unaware of.