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

[Snoredog]

Not what you call scientific controlled study, but a real world side-by-side comparison of the noise levels between two mfg machines.

I am using a Radio Shack digital Sound Level Meter, just like the one you can buy at your local Radio Shack store. The meter is placed on a camera tripod so it does not influence the measurement. The RS meter can only measure sounds from 50dB to 126dB range. The meter was placed close to the machines because of this minimum sound limitation. The meter was not moved between tests.

Both machines were tested with a standard hose connected with a UMFF mask on the end. The hose is pulled out straight from the machine across the bed in both tests. Both machines were allowed to run wide-open which is the loudest they should ever get.

On the left you see my older Remstar Auto w/Cflex. If you observe the sound meter at the bottom it says 60dB. This value is the same using Fast or Slow sampling rates or A or C weighting. The meter displays a integrated average between the Min and Max readings, 60dB is that average.

A-weighting has a A-curve frequency characteristics. This setting causes the meter to respond mainly to frequencies in the 500-to-10,000Hz range, which is the human ear's most sensitive range.

C-weighting has a C-curve (flat) frequency characteristics. This setting causes the meter to respond mainly to frequencies in the 32-to-10,000Hz range. C is mainly used to measure musical material.

Sound meter was NOT moved only the machine was swapped out and retested this time with the new M series Auto. Both machines were turned on and allowed to run wide open with no restriction other than a standard hose and mask.

The old Remstar auto (LEFT) measures 60db (avg).
The new M series Remstar auto (RIGHT) measures 61db (avg).

A 1db difference is seen, M series is louder according to the meter (I was wrong). You will note that due to the difference in size the M series machine is actually shown closer to the meter. Meter was bouncing from 60-61 when camera snapped the picture, where the old model was a solid 60db was seen. So in reality there is probably no real difference in noise levels between these two machines.

Measuring a distance of 36" from the machine, noise level drops to <50db and is beyond the range of the meter to detect sound levels for both machines. 36" is roughly the distance from the center of the machine to the center of my pillow.

So when you read the M series machine is so noisy, always ask:

as compared to what?

I always like the one, I'm new, this is my first cpap machine, it sure is noisy, noisiest machine I ever used. Like me, some of you have owned several machines and know the difference in noise levels between machines, nearly all of today's machines are quiet compared to the machines of 5 or more years ago.

If you can detect the difference between .5 and 1dB your hearing is much better than mine.

[sleepyinsunnyvale]

Did you try taking separate sound levels for each side and the top and bottom of the machine? That's how generally do sound levels of electronic equipment to establish a spec during development.

[DreamStalker]

Not what you call scientific controlled study, but a real world side-by-side comparison of the noise levels between two mfg machines.

I am using a Radio Shack digital Sound Level Meter, just like the one you can buy at your local Radio Shack store. The meter is placed on a camera tripod so it does not influence the measurement. The RS meter can only measure sounds from 50dB to 126dB range. The meter was placed close to the machines because of this minimum sound limitation. The meter was not moved between tests.

Both machines were tested with a standard hose connected with a UMFF mask on the end. The hose is pulled out straight from the machine across the bed in both tests. Both machines were allowed to run wide-open which is the loudest they should ever get.

On the left you see my older Remstar Auto w/Cflex. If you observe the sound meter at the bottom it says 60dB. This value is the same using Fast or Slow sampling rates or A or C weighting. The meter displays a integrated average between the Min and Max readings, 60dB is that average.

A-weighting has a A-curve frequency characteristics. This setting causes the meter to respond mainly to frequencies in the 500-to-10,000Hz range, which is the human ear's most sensitive range.

C-weighting has a C-curve (flat) frequency characteristics. This setting causes the meter to respond mainly to frequencies in the 32-to-10,000Hz range. C is mainly used to measure musical material.

Sound meter was NOT moved only the machine was swapped out and retested this time with the new M series Auto. Both machines were turned on and allowed to run wide open with no restriction other than a standard hose and mask.

The old Remstar auto (LEFT) measures 60db (avg).
The new M series Remstar auto (RIGHT) measures 61db (avg).

A 1db difference is seen, M series is louder according to the meter (I was wrong). You will note that due to the difference in size the M series machine is actually shown closer to the meter. Meter was bouncing from 60-61 when camera snapped the picture, where the old model was a solid 60db was seen. So in reality there is probably no real difference in noise levels between these two machines.

Measuring a distance of 36" from the machine, noise level drops to <50db and is beyond the range of the meter to detect sound levels for both machines. 36" is roughly the distance from the center of the machine to the center of my pillow.

So when you read the M series machine is so noisy, always ask:

as compared to what?

I always like the one, I'm new, this is my first cpap machine, it sure is noisy, noisiest machine I ever used. Like me, some of you have owned several machines and know the difference in noise levels between machines, nearly all of today's machines are quiet compared to the machines of 5 or more years ago.

If you can detect the difference between .5 and 1dB your hearing is much better than mine.

Nice experiment SD. Is it possible that although they have the same noise sound level that the frequency of the noise is different? It may be that some people are more sensitive to different sound frequencies. I guess you would have to use an oscilliscope.

- r

[oldgearhead]

It may be that some people are more sensitive to different sound frequencies.

I think DreamStalker has the answer. However, wouldn't all the users need
a complex hearing test to determine which machine is for them?

Snoredog - Great post!

[sleepyinsunnyvale]

wouldn't all the users need
a complex hearing test to determine which machine is for them?

No. Sound specs are written, and test procedures followed, that gets the subjectivity out of the picture.

One could use a spectrum analyzer to examine the frequency content of the noise. What you would like to see are no noise peaks showing up at any frequency or frequency range. White noise, in other words
I have also seen noise measurements done across the band of interest (32Hz to 10KHz in tis case) but using filters to measure only one octave at a time starting at 32Hz and ending at 10KHz

[Justin_Case]

A 1db difference is not bad. Many people will probably not notice a difference. I am quite anal when it comes to sound, music, and noise. In my side by side comparison with my spouse in the room, we both could hear a FREAKEN big difference. My DME warned me about it, but honestly in his office it wasn't untolerable, mind you his office was quite loud to begin with the air conditioning on. The noise only became untolerable at home, on the floor or on the bed table. It made no difference.

I dunno, maybe us folks in Canada get different machines than you folks in the US. Or maybe it's just one of those things where some batches are noisier or than others.

I wish I had a sound meter to provide objective sampling to show y'all.

[JM]

If memory serves, it takes an increase of 3db to make a perceptible difference and there needs to be an increase of 10X to double the sound level. Also. the adult ear starts to loose its sensitivity to the higher frequencies, so instead of 20Hz - 20kHz it's more like 20Hz - 16kHz.

JM

[Guest]

I think this proves that much like masks, everyone is going to be completely different! One persons quiet is going to be another persons racket.

[Vader]

My ears are pretty good, and while I do notice a difference in frequency between the classic and M series, I can't hear a big discernable difference in sound level.
OTOH, who's to say that the M series are all consistent with one another?

[dsm]

Snoredog,

Got start & an interesting test.

I agree with the poster who suggested testing from 2-3 angles but really the only angles that count are the ones where our heads are in relation to the machine.

Also I agree with the poster who raised the issue of noise type.

A machine whining up & down (VPAP III) is a lot harder to take at 50db than a machine putting out 60db of constant noise (F7p machines).

Also the frequency bad does make a big diff - vpap III is high pitched the F7p machines tend to be very low piched noise.

Cheers

DSM

[Guest]

If someone thinks their cpap or apap is loud, besides putting it on the floor, can they do something simple like put a towel over it or something like that to lessen the noise?

[Guest]

If noise is a problem, how about building a sound deadening box that has an opening for the hose to enter and a filter/screen area for air to enter? I'll make em if people want em.

[Justin_Case]

Anytime you try to build a box for a xPAP, you risk burning out the motor if there is not enough airflow.

The better alternative,if there is room is placing the machine under the bed; however, if you're sensitive to noise in general like me, I notice the noise not only coming from the machine but within the mask and hose too. In all areas, the M series was noisier but oddly enough, it did a much better job in controlling my apneas for the short period of time during the night I was using it.

I don't think that all M machines are equal when it comes to sound, In fact, I have swapped the Auto Pro a few times and I notice a slight difference in the sound between the same models.

[Snoredog]

[quote="Anonymous"]If noise is a problem, how about building a sound deadening box that has an opening for the hose to enter and a filter/screen area for air to enter? I'll make em if people want em.

[ozij]

If noise is a problem, how about building a sound deadening box that has an opening for the hose to enter and a filter/screen area for air to enter? I'll make em if people want em.

I usually keep my machine (a PB 420E0 in a an IKEA two drawer chest, in the bottom drawer. I line the bottom of the drawer with bath towerl (not too soft, the machine doesn't sink in it) and another towel at the back wall of the drawer.

This makes a major difference in noise compared to keeping the machine on a chest, at ear level, as I discovered recently when sleeping away from home..

It may be relevant that that the floor is of stone, not wood.

When morning comes I diconnect the electricity, take out the humidifier tank, and slip the drawer back in.

O.

The towels get changed every now and then, to make sure they don't accumulate too much dust.