Are more channels better?

Hearing Aids
1

The new Siemens Pure Micon 7mi has 48 channels vs the 5mi, which has “only” 32. 32 channels is twice what my current 3 year old Phonak Audeo Yes has (which is just about obsolete for me now with my deteriorated hearing).

Maybe some Audi’s out there can help me. I researched what a channel is and found the following article that explained bands and channels, and according to this article tons of channels may really not be necessary at all. I guess the 7mi HA also has an automatic directional capability (if you want to zoom to a particular side or to the back of you), and the 5 mi you have to turn it on on the HA itself. I suppose you would really just need this in a car? The price difference is $1500, which is quite a bit. What do you think? I would be using two binaural HA, with a superreceiver in the bad ear.

With HA’s being replaced every 3-5 years, shelling out $6K, vs 4.5K for the 5mi is quite a bit…unless you think it really will make my hearing that much better, especially in noisy environments (which is another point they are selling).
Making sense of the hearing aid lingo: what’s the difference between channels and bands… and how many do I need?

Posted on June 21, 2011 by Patrick Freuler | 1 Comment
This post might be for the more technical folks out there interested in the inner workings of hearing aids (we at Audicus HearingAids are proud tech geeks). Whoever has done a bit of research when shopping for hearing aids probably had to wrestle with confusing terminology at some point. With hearing aids becoming increasingly packed with features and gimmicks, it’s important not to lose the overview on the basic indicators.
What are Hearing Aid Channels and Bands?

Two of the most important characteristics of hearing aids are “Channels” and “Bands”… which are also some of the most misunderstood by users.
To start off with, the number of channels or bands has nothing to do with the number of programs or volume settings. Sounds are processed and amplified by a hearing aid based on frequencies (or the pitch of a sound) and volumes. A peek at your audiogram will tell you how much amplification you need for any given frequency. In a nutshell, bands and channels thus determine how granular a hearing aid can process and amplify the sounds it perceives. To quote a great explanation from Philips:
“A band is what is used to control volume in different frequencies. This allows us to adjust more volume in a specific area of your hearing loss without effecting other areas where you might need less volume The more bands the hearing aid offers the more room we have to fit the aid to your hearing loss.
Channels break up the frequency range into individual channels. This allows the hearing aid to differentiate noise from speech. The more channels the hearing aid has the more fine tuned it can be. For instance the sound of keys falling on a table, or water running in the sink may be overwhelming. When your hearing aid offers many channels we can adjust each frequency that is too loud without sacrificing the things you want to hear, like your spouse or boss.”
Thus, just the way a high-resolution picture gives you a sharper image, more bands and channels provide you with a more granular sound quality. More channels will provide better “resolution” on the frequencies and more bands will mean better “resolution” on the volume… thus allowing your hearing aid to match your audiogram more accurately.
But at what point does a higher degree of accuracy become redundant? For example, take a look at the two pictures below:

One has twice the resolution of the other - however most people can hardly notice the difference. The same applies to hearing aids.
How many hearing aid channels are too many?

Some modern devices can come with more than 24 channels… and cost patients Thousands of Dollars more. But how many channels do we really need for the everyday use?
Starkey, a hearing aid manufacturer, did a study involving a sample of 1,156 audiograms to answer the question “how many independent signal processing channels are required to maximize speech audibility”. The underlying assumption was that the goal of a well designed hearing aid is to maximize sound quality and speech understanding – as measured by the articulation or “AI Index”. They found that the perceived benefit in speech audibility beyond 4 channels is marginal, or “statistically insignificant”. The most drastic improvement occurs when moving from 1 to 2 channel devices.


So if most patients (especially those with mild or moderate hearing loss) can’t hear the difference beyond 2-4 channels (all Audicus hearing aids come with 2-6 channels, by the way), why are manufacturers continuously pushing for more channels and bands? One possible answer is that it allows them to pass through continuous price increases year over year, by calling it “superior” technology. Sure, “superior” it is, but “over-engineered with a negligible benefit” might be a better term.
Most importantly though, patients have the right to be better educated by the respective professionals about what they spend their money on - especially if it’s in the Thousands of Dollars - and ultimately have more choice in the decision process. It’s time that manufacturers put “actual perceived user benefit” back in the equation - which is something we at Audicus Hearing Aids are particularly passionate about.

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Channels are also used for noise reduction. More can be better.

That advert you posted is simply trying to cover up the fact that they don’t offer many channels - or other goodies.

3

Thanks. As a specialist, do you think I’d get the benefit from the extra dollars from 48 channels vs. 32 (per my stats)?

Another thing I’m a bit peeved at is that I can’t do a week trial run. I have to pay for the whole thing up front with a 30 day trial, and then if I don’t like them it’s a $150 restocking fee. I know someone else who is in the market for HA, and both audiologists he’s gone to has let him take them and use them for one week. Which is more typical in your opinion?

4

i have not “heard” the micons as of yet, so i cannot speak to their sound quality.

places will vary greatly…i have only ever dispensed at places where we required all the money either at the time of order or the time of delivery; i have never worked anywhere that we let the patient take the hearing aids out without some sort of payment.

places like costco will let you walk around with the hearing aids in and try them out but they will not let you leave the store with them unless they are paid for. sorry!

5

If you’ve read what you copied from the sites then you have at least a rough idea of what channels are.

It’s worth pointing out that your typical hearing test checks your hearing at only 6 to 10 frequencies per ear. Going from a 4 channel to an 8 channel hearing aid could be beneficial in the sense that it could more accurately fit your hearing test results. I wouldn’t expect going from a 32 to a 48 channel instrument to offer any noticeable difference. Really, once you get past a dozen or so channels the extra features and enhancements are going to make a bigger difference to you than a simple increase in channels would.

Heck, if you really want to go crazy with it, Sam’s Club offers a 64-channel hearing aid! My understanding is that (based on features included) it’s comparable to a major manufacturer’s entry-level models, but hey: it’s got 64 channels! :wink:

6

Ah yes the 64 channel aids. It was I think 6 years ago when America Hears came onto the scene with their 64 channel aid. The hard of hearing community went crazy as they also allowed us to program the aids from the comfort of our own homes. but then we tried out the aids and were brought crashing back down to earth. many were not happy with the 64 channel claim and believed it was misleading. And soon afterwards the 64 channel claim disappeared from their website.

channels in the hearing aid world should only describe the aid’s ability to adjust the gain and/or compression directly for a range of frequencies.

anything above 22 channels is probably referring to the noise reduction algorithm in the aid.

7

This is what I’ve been told and I kept to show my parents. I personally didn’t notice the difference between 6 channels and 16 channels :slight_smile:

It tells you nothing. Linear isn’t always best for profound losses - its better for profound conductive losses, profound sensorineural losses will usually use compression.

In any case, the assertion that having one channel is linear is just plain wrong. It can be as compressed as you like.

The more channels you have, the more separate keys on the keyboard you can separately control the intensity of the sound over. It’s quite believable that you would not hear the difference with more than six in a flat profound loss, however if your loss is steeper or has more variation, or you need to hear better in competing mechanical noise situations, more channels may be beneficial.

IMHO I have a sneaking suspicion that more than two channels per octave is overkill, so if you consider that a receiver is operating from 250/500 to nominally 8 kHz (5-6 octaves), that gives you a maximum of 10-12 channels at the optimum level. Again, these would only be fully required if the loss changed a significant amount across two adjacent channels.

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These are extremely helpful and insightful responses! I never considered that my hearing test is probably on tested on 10 frequencies or so, so how can 48 channels be any more efficient than 32? Of course, they don’t want to tell me this because i won’t spend the extra $1,500 on the upper end model. I like the Keyboard analogy and that story of the 64 channels.

These boards are great. I don’t feel like such a dunce when I go in to my appts.

Tisha

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Tisha,
Channels do make a difference but how much is relative to the severity of the hearing loss. As was explained above the more channles the more fine tuning the gain can be modified at select frequencies.

If your hearing were moderate or slight severe(which it is not) then you frequency band stays constant over a select range. Thus need less channels as the gain does not need to be modified so often.

I saw an ad for a company called tru hearing which sells almost most manufacturer hearing at reduced prices. Also has 3 year loss/Damage guarantee on several manufacturers.

Catch??? Tru hearing will send you to a local audiologist who is turn will reduce the services offered. Typically instead of life time followup office visits it will then charge you after the first year($35) each time.

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Naida,
I agree that just more channels is not the complete answer. Hwoever, the more channels you have does allow for more frequencies to be programmed.

It all depends on the hearing loss and how many abrupt changes over the critical range you need.

Along with channels is compression algorithms, noise reduction, directional microphones, adaptive filtering. Since the manufactures don’t really have hotlines to allow customers to ask detailed technical questiuons it is assumed the audiologists know these specifications thoroughly which has not been my experience to date. Thus deciding which hearing aid is best soemtimes comes down to trying many out which is time consuming and difficult to measure quality.

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well not having a clue has never kept the uninformed from posting ‘fact’ on a thread.

12

Lets get basic. A Channel should mean a slice of the hearable audio spectrum which the aid can control the loudness AND compression and possibly other parameters… A Band is a slice that you can only control how loud it is (gain) and narrows the noise gate.

Many experts think that the majority of loss types require only 4 to 6 channels.

There is a penalty to more channels…more means increased processing time which can lead to conflict with the sound coming through the vent which has zero processing time. And each additional channel increases the amount of inter-channel distortion and phase shift to the input signal.

So more is not always better.

It is a rare patient that benifits from more than 4 to 6 channels (notching out distorting hair cells.)

For most losses the only benifit to lots of channels is increased cost and more profit for the manufacturers and retailers. Ed

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That’s why personally someone with a flat loss won’t notice the different between having more channels like myself.

14

However it does give the audiologist/dispenser more tools to deal with pitch specific problems. If you’ve ever programmed an aid, you’d realise that not having a gain ‘handle’ at a particular frequency can be quite debilitating to the process. (Like having occasional feedback just at 3Khz and only having 2KHz and 4 Khz controls.)

Just one caveat about the ‘flat losses’ as they appear on the audiogram: yes, that might look like you can just whack in one gain setting: in reality your canal resonance added to the insertion gain/loss of the device will produce a pretty squiggly line. Coupled with this, the output of the receiver is a damped sinusoid saw-tooth in it’s natural state. Put all these things together and you have the potential to be massively askew at a particular frequency - in terms of the actual gain needed.

Now, as to the actual resolution: if you follow the articulation index measure that each octave contains roughly 20% of the speech cues (with a greater bias in the 2-4KHz area), you have a starting point. If you remove one of these octaves entirely to deal with a feedback issue, then you have eliminated the response from up to 20% of your potential speech area. I appreciate that there are other factors at play: including the roll-off between each channel and the efficacy of different feedback systems, but ultimately, if the aid is whistling, you have to turn down the gain a bit at that point - whether you do it obviously or not.

This leaves us with a trade off - how many channels is enough, how many is too much? - (NB Bernafon). Ultimately this is a design choice based on the parameters of the circuit, especially the clocking speed: going forward its going to be less of an issue due to Moore’s Law. In a previous response on here I postulated that a 10-12 channels was probably enough, given that it adequately represents every conceivable audiogram, provides half octave accuracy for the feedback issue and allows frequency specific noise management to function properly with minimum disturbance of the adjoining channels. More than 12 channels is probably chewing more processor cycles than absolutely needed, but if you have the lateral capacity on your chip, why not, if there is a potential improvement in the end signal.

I’d like to address another point in relation to the alleged ‘inter channel distortion’ or ‘compression artefacts’; you can bet your bottom dollar on the fact that whatever you think of the electronics engineers at a modern hearing aid factory/design house, they are doing their absolute utmost to prevent such issues. Likewise the delay within the circuit. Nobody benefits from more rubbish being thrown at their residual hearing.

Going forward, simultaneous binaural processing is pushing the aids to do more with the incoming signal on both sides, so the number of channels per aid will effectively double as the processing of the stereo signal can be done separately to improve performance in background noise with a combined decision on the output to each ear.

In conclusion a dozen channels is probably enough: that much used study illustrating the patient benefits of less than half a dozen channels doesn’t actually have great credibility at all when you think about it, as the patient is unaware of what they are missing in all situations, therefore they can’t tell relatively how effective an aid is being in those situations. It might sound prescriptive, but you can’t ever appreciate the full effect of a view from inside, can you.

NB: Bernafon - Channel free or 10,000 channel technology has been around for a few years; having fitted quite a few in the past, some people really like the kind of performance, some don’t. It’s a shame that their not one of the ‘main’ manufacturers as this delivery mechanism will always be considered a bit ‘second string’ in the DeMant catalogue.

15

hotrod, It sounds like you’d prefer to work with a professional who is well versed on what the different hearing aid features are and is able to explain them to you effectively. A good strategy for you might be to call around to different offices and ask to speak with the professional there over the phone. Tell them that you’re interested in new hearing aids, but had a few questions you hoped they could help you with before coming in. From there ask about the features you’re curious about and see whether or not you like the answer you’re given. This could be a quick method for you to choose a professional who keeps up to date on the latest technology and is able to differentiate between marketing hype and real features.

It doesn’t happen too often, but occasionally I’ll get such calls myself from people who have done their homework and want to make sure I have too.

16

ED,
You seem to have a feel for some of the terminology.

WHat do you think of Resound Forza hearing aid(made fro Costco)?
Resound claims - 15 bands
Then claims 15 channels are the same
Then the sofwtare shows 9 gains + 6 compression ration fields to change.

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The best explanation of channels/bands and the effect they have on speech perception both in quiet and noise that I have read is from Jason Galster at Starkey Labs.

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to oversimplify. If the processor speed is fast enough , more channels will give better sampling and control? If the noise attenuation function can process that much smaller a portion of the total, fast enough, then that is a positive? I used to have a precipitately sloping loss, it has now flattened out. I am willing to accept that I have fallen for the tech sales pitch. I have Phonak aids with the spice chip and believe that my 20 channels and all the gizmos can be handled processing speed wise. The difference between 16 channels and 20 may be insignificant, but in my little opinion 12 to 20 might.
If hoh folks can find a level of aid that satisfies or fills appropriate, then that is the way to go. Everyone is different
some pro should explain: loss of frequency and temporal resolution
can aids detect speech you want to hear from speech you don’t.
Can speech as babble (in the background) be distinguished