Noise level comparison - Old Remstar Auto vs. New M series

-SWS wrote:

...though have seen some people say that a batch of Mexican manufactured models were noisy.

The Mexican manufactured 420e model (informally known as the "siesta model") is programmed to facilitate taking a nap every afternoon during the heat of the day---preferably while leaning against a store front in an eerily quiet village. Some people confuse the Spaghetti Western music that it softly plays as if it were unwanted CPAP blower noise. "Regional" design features... Gotta love 'em.

The other point that I'd like to toss up for consideration is that of manufacturing variation. So far most models (not including the very latest "tiny" PAPs from the two big "R" companies) have been reported to contain a surprising amount of sound variation from one production unit to the next.

In my view taking one, two, or even three of the same model from each manufacturer, then generalizing sound characteristics across tens of thousands of same-model machines, is not an ideal way to "sound rate" or even "sound compare" CPAP models.

I don't believe that any one brand/model is going to vary that much that it can't be 'characterized'.

Actually Snork couldn't sleep with his first Remstar Auto, but found his second one quite tolerable. Rested Gal found her first 420e considerably louder than her second 420e. I found my first Remstar Auto better than my highly annoying second Remstar Auto. My third Remstar Auto had C-Flex and was just as good as my first Remstar Auto. There are plenty of similar anecdotes.

Audio characteristics are the sum total of the entire assembled unit. If you can look at a CPAP machine and assess all possible acoustic harmonic variations from all possible mechanical component tolerances, you are a far more talented engineer than I am. I can't even come close to doing that, nor have I had any colleagues who could. .

-SWS wrote:

I don't believe that any one brand/model is going to vary that much that it can't be 'characterized'.

Actually Snork couldn't sleep with his first Remstar Auto, but found his second one quite tolerable. Rested Gal found her first 420e considerably louder than her second 420e. I found my first Remstar Auto better than my highly annoying second Remstar Auto. My third Remstar Auto had C-Flex and was just as good as my first Remstar Auto. There are plenty of similar anecdotes.

Audio characteristics are the sum total of the entire assembled unit. If you can look at a CPAP machine and assess all possible acoustic harmonic variations from all possible mechanical component tolerances, you are a far more talented engineer than I am. I can't even come close to doing that, nor have I had any colleagues who could. .

DSM wrote:Perhaps you are looking from a much broader perspective ?.

Yes, DSM. That's precisely my point. That a much broader sample would be needed to assess this particular facet of machine quality. This discussion was all about quality of sleep afforded by the sound quality of these products, was it not?

I think your statement goes more toward being able to identify a particular salient acoustical characteristic driven by the physical characteristics of a blower motor, does it not? By contrast my statement was aimed at the sum total acoustical output from any given machine model. I had a Resmed Autoset for a short while. It was even louder than my second Remstar Auto. After I disassembled and carefully reassembled the unit, it ended up being quieter than my best Remstar Auto or my 420e.

Do you agree that having a simple "look-see" at the blower motor could not have come close to predicting the two variations in sound quality relative to the two manufacturing processes that particular Resmed Spirit went through (factory assembly followed by my own reassembly)?

SWS,

I can only repeat my prior post, verbatim

DSM

dsm wrote:SWS,

I can only repeat my prior post, verbatim

DSM

Okay. I looked your prior post over carefully. It tells me that you can identify certain salient sound characteristics from a couple same-model machines you have seen. But how does that relate to my first two identical Remstar Auto models: one was whisper quiet and the other was too annoying to sleep with? And how does that sound-identification ability relate to the very loud Resmed Spirit that I had to reassemble?

I'm still totally confused about how being able to expertly identify a couple/few same model machines by ear can project a quality grade, or project a sample-wide pitch variation across a pressure/impedance spectrum, or even project a standard deviation measurement for any given acoustical spec across any model's entire production run---- let alone many production runs for that same model?

Call me dumb. I don't get how identifying three VPAP III's by ear can project adequate statistical controls or assessments across thousands of machines. .

-SWS wrote:Actually Snork couldn't sleep with his first Remstar Auto, but found his second one quite tolerable. Rested Gal found her first 420e considerably louder than her second 420e. I found my first Remstar Auto better than my highly annoying second Remstar Auto. My third Remstar Auto had C-Flex and was just as good as my first Remstar Auto. There are plenty of similar anecdotes.

I'm glad you brought this up because I have 2 identical machines -Remstar Auto with c-flex - both purchased new and the sound varies alot. One is whisper quiet and one is loud. I was surprised to find the very same model machine could be so different in the noise it produced. I guess sometimes its just luck of the draw.

Lori~

Why does this happen? How come people with two of the exact same machine get such different noise levels? Is it a quality control issue? It seems people report this phenomenon with different manufacturers, so I was wondering if it is possible it happnes during shipping because the machines get banged around too much?

Anonymous wrote:Why does this happen? How come people with two of the exact same machine get such different noise levels? Is it a quality control issue? It seems people report this phenomenon with different manufacturers, so I was wondering if it is possible it happnes during shipping because the machines get banged around too much?

Good question.
But shouldn't the machines be packed so that nothing happens to them in transit?

Suppose they use different internal compnents e.g. fans created by different manufacturers and bought by the batch wherever they're found?

I wonder if - when checking the machines before OKaying them - the protocol includes noise production.

O.

Guest, Ozij- my hunch is that a variety of issues contribute, including quality control at the manufacturers' factories as well as the factories of their component suppliers. In the case of the Resmed Spirit I had, the annoying sound was air turbulence. Disassembly followed by careful reassembly fixed that problem. Don't know if that out-of-tolerance fit occurred in the factory, gradually in the field, or perhaps even in transit on a delivery truck.

In the case of my second Remstar Auto, the blower motor or fan blades sent an annoying up-and-down mosquito-pitched whine my way via the CPAP hose as if it were a perfectly designed acoustical waveguide for that particular pitch range.

Someone on TAS once posted a link to an internal Resmed memo that conveyed the results of their own investigation into field complaints about noisey machines. I kind of vaguely think that memo may have concluded their own third-party component supplier sent out a batch of blower motors that just so happened to mechanically resonate at the wrong pitch. Reading that study I got the impression that statistical quality controls were not routinely employed by Resmed regarding acoustics in particular.

Reading other people's anecdotes throughout quite a few years, I formulated the impression that in all likelihood all the manufacturers need to improve significantly regarding this particular facet of quality----that, deny it or not, is genuinely crucial to so many patients already struggling with the comfort issues of CPAP therapy. I would personally identify this as a potential area for improvement with most or all manufacturers---especially when they release one simple noise spec such as <30 dB. I agree with DSM and the internal Resmed memo: the issue tends to be one of pitch. I would really like to see much better statistical controls employed in this area of manufacturing---and I would like to see those statistical controls extended all the way into the field, post-delivery.

-SWS wrote:In the case of the Resmed Spirit I had, the annoying sound was air turbulence. Disassembly followed by careful reassembly fixed that problem.

I am green with envy. That must give an enormous sensed of empowerment (....there, I used that word).

Thanks for the rest of the info.

I would personally identify this as a potential area for improvement with most or all manufacturers---especially when they release one simple noise spec such as <30 dB. I agree with DSM and the internal Resmed memo: the issue tends to be one of pitch. I would really like to see much better statistical controls employed in this area of manufacturing---and I would like to see those statistical controls extend all the way in to the field, post-delivery.

(my emphasis)

When you become a consultant to one of those companies, - and they accept your suggestions - drop us a hint, OK? I want to know which machine to buy when this one dies (of old age, I hope). And, since you will no doubt recommend Rested Gal for the mask design division, we'll really be flying (or sleeping, as it were).

I guess we can't get every company exec to sleep with a cpap - but sleeping with a cpap (at various pressures) recording should be mandatory training. For a week?

O.

-SWS wrote:I would really like to see much better statistical controls employed in this area of manufacturing---and I would like to see those statistical controls extended all the way into the field, post-delivery.

Wouldn't that be something? I suppose it's too much to expect that each machine is tested in the factory for sound level/pitch compliance prior to being shipped out. But I would think better safeguards in the consistency of each part no matter where it comes from, and at each step of assembly would go a long way towards solving the problem. I'm surprised they aren't already in place. Probably when they set out to manufacture these machines they didn't realize they'd soon develop such a discerning audience.

As far as post-delivery, it might be hard to setup and enforce standards for testing, but if it was required and done correctly, the manufacturer would likely get a lot of returned machines.

When I was researching Respironics quality control to try to find out more about this subject, I came across a bunch of current job openings on their site for engineers and some of the areas are: Research and Technology, Quality, Compliance, etc. Maybe someone from this forum would like to move to Pennsylvania and get a job! It would be nice to have a mole on the inside! (Not to spy, of course, but to ensure the quality we deserve!)

This therapy is hard enough without having to deal with machines that don't meet the sound level thresholds. If you got one of the loud ones and didn't have anything to compare it to, you might think all machines were like that. It's probably another reason so many people give up, which is a real shame considering most of these machines (properly assembled with proper parts) are pretty darn quiet.

My guess is that they're more interested in production and getting them out to their "customers" (the DMEs). Do they care where they go after that?

The employees that work in the "final setup and testing" areas probably wear hearing protection and don't know or don't care. They're all nice and quiet to them.

They know that, statistically, a good percentage of them are going to end up in closets (sooner or later). Those are the ones that are REALLY quiet.

They know that many of the users probably haven't spent much time with the machines before, let alone to have been able to compare the sounds from one brand/model to another.....(so they won't know the difference of how quiet they are or not)

SO.....we get down to just a few noisy ones that end up coming back to the factory for "repair". It's definitely more cost effective than to make sure they're all quiet when they leave the factory.

It's your "luck of the draw".

Just my 3 1/2 cents worth.

Den

Well come on. I don't think it's really at all reasonable to expect that each and every machine (That anyone makes) is personally tested for percieved noise and pitch levels before going out. That seems fairly ludicrous to me. Not on the scale we are talking about here. If this was a closet operation putting out 500 or so a year that might be one thing, but for a company that is putting out tens of thousands a year that's getting insane.
Not to mention that the glaring huge fact that this thread has pointed out is that "quiet" and "acceptable noise levels" are vastly different from one person to the next.
So they do what any reasonable business does - they set tolerence levels and then (I'm sure) test a statistically relevant percentage of machines to make sure they are within tolerance.

I noticed something making a sound when I would turn my BiPAP over to put it in the carrying case, so I opened it and found that the motherboard was not securely attached to the four black posts upon which it rests. I'm going to use electrician's tape or such to fasten it dow. Assuming this board should be battened down, as every other one I've ever seen is, it could be causing some vibration.

1) Does anyone know if the board is loose in thier RemStar?

2) -SWS, you mentioned re-assembling yours. Did you just make sure everything was tight? I assume that the lefts to lefts, rights to rights, reds to reds and whites to whites situation is okay, because it runs.