Epiphany on PRS1 Noise

[archangle]

I don't know if I've just been being dense before, but I just realized that much of the noise I hear with a PRS1 machine is coming down the hose, through the mask, into my nose, and getting into my inner ear through my nose and head tissue, not through my outer ear.

I noticed this because I changed from an S9 to a PRS1 machine, and I also turned of the fan and other noise sources that are usually going when I'm CPAPing. I kept noticing that the noise I heard seemed to come from the right side, and my machine is on the left side. If I put my hands over my ears, I still hear the sound. I actually hear it even louder.

I find this doesn't happen if I use the S9 machine.

This might be part of the reason some people seem to have a particular problem with noise for PRS1 machines, and why it seems to vary so much from person to person. Maybe the "internal hearing" sensitivity varies between people because of sinuses, Eustachian tube, skull density, skull voids 8-), etc.

It also means that some of the recommended noise reduction measures like boxes, drawers, etc. might not work for some people.

Does anyone else find that the PRS1 noise seems to be coming through the hose into your nose, not your ears?

[Ghost1958]

I don't know if I've just been being dense before, but I just realized that much of the noise I hear with a PRS1 machine is coming down the hose, through the mask, into my nose, and getting into my inner ear through my nose and head tissue, not through my outer ear.

I noticed this because I changed from an S9 to a PRS1 machine, and I also turned of the fan and other noise sources that are usually going when I'm CPAPing. I kept noticing that the noise I heard seemed to come from the right side, and my machine is on the left side. If I put my hands over my ears, I still hear the sound. I actually hear it even louder.

I find this doesn't happen if I use the S9 machine.

This might be part of the reason some people seem to have a particular problem with noise for PRS1 machines, and why it seems to vary so much from person to person. Maybe the "internal hearing" sensitivity varies between people because of sinuses, Eustachian tube, skull density, skull voids 8-), etc.

It also means that some of the recommended noise reduction measures like boxes, drawers, etc. might not work for some people.

Does anyone else find that the PRS1 noise seems to be coming through the hose into your nose, not your ears?

Skull density or skull voids huh?? Polite way of saying thick headed or empty headed. ??

I must be one of the two cuz other than my own breathing i dont really hear the machine much at all.
But when I first started I placed it on an old empty toy box that was the right height etc. I heard it pretty plain then until I figured out that the empty wooden box was acting much like a acoustic guitar box and amplifying the sound quite a lot.

Put a towel under the machine and really dont hear the machine itself just my own breathing. But I hear that without a mask on also.

[DocWils]

While you switched machines, did you also switch masks and hose types as well? The best way to "blimp" a CPAP is to isolate it from what it is sitting on ( a few folded towels or some computer foam will do the trick) as much of the noise is conducted vibration form the motor. If it is the humidifier tank making the noise (the PRS has a noisier tank design than the s9 for tank echo - all those internal ridges and a larger open space - daft design, IMHO, plus the front of the tank is exposed, which the s9 has the entire tank enclosed) then wrapping a few towels over the front of the humidifier cuts that noise adequately. If it is coming down the hose, then a hose covering usually takes care of that. The only way for this to be conducted to your right ear is if your Eustachian tube is somehow open. Make sure your EPR is set correctly, and the mask setting is correct for the mask type.

[archangle]

Same hose and mask. I literally moved the PRS1 over and moved the S9 in, just swapping the hose on the back of the machine.

I have a standard non-heated Respironics hose and a Swift FX nasal mask.

I'm pretty sure the noise is coming into my nose, vibrating the tissue there, and conducting internally through my head into my inner ear. It's a bit like how Beethoven and Edison would listen to pianos or gramophones by resting their teeth on them. Look up "bone conduction."

I get a similar effect if I put my teeth on something vibrating like the handle of my electric toothbrush.

I still heard the noise just as loud if I put my hands over my ears.

[DocWils]

Did you check that you have the correct hose size settings on the PRS?

[justMongo]

While you switched machines, did you also switch masks and hose types as well? The best way to "blimp" a CPAP is to isolate it from what it is sitting on ( a few folded towels or some computer foam will do the trick) as much of the noise is conducted vibration form the motor. If it is the humidifier tank making the noise (the PRS has a noisier tank design than the s9 for tank echo - all those internal ridges and a larger open space - daft design, IMHO, plus the front of the tank is exposed, which the s9 has the entire tank enclosed) then wrapping a few towels over the front of the humidifier cuts that noise adequately. If it is coming down the hose, then a hose covering usually takes care of that. The only way for this to be conducted to your right ear is if your Eustachian tube is somehow open. Make sure your EPR is set correctly, and the mask setting is correct for the mask type.

Be careful when setting an S9 on soft material. The intake is at the bottom of the filter cover. And, you can easily choke off the intake.

I've noticed that if I swallow before I fall asleep on the machine, it must pressurize my inner ear. I think my malleus, incus, and stapes must be fused as I cannot hear much. Indicating the transmission system of the inner ear can no longer compensate for pressure variation. (Old Age!) I like to listen to music or deutsch lessons as I fall asleep.

[archangle]

Did you check that you have the correct hose size settings on the PRS?

Yes, but thanks.

The noise doesn't usually bother me. It's just that I noticed this is how the noise seems to get to me, and it probably affects those who are having problems with the noise on a PRS1. If the noise is coming in this way, a lot of the ideas for noise reduction won't work. For instance, putting the machine in a box, under the bed, or using earmuffs won't help.

[DocWils]

I would almost be certain that if the noise is travelling down the hose, it is reaching your ear due to an open Eustachian tube, rather than bone conduction, but that is only an educated guess. For bone conduction, you would need a fair amount of outside noise and vibration, and some tightly clamped shut teeth, but of course, just an educated guess (based on my education). But yes, if that is the noise source, then putting it in box or something is not going to help - isolating the hose might, though, as a fair amount of the noise conducted down the hose is from the vibration of the hose as air rushes past.

I don't think putting the machine in a box ever is a good idea, if only because you would limit the available air for the machine to use. Under the bed? Dust source supreme.

[archangle]

I don't think putting the machine in a box ever is a good idea, if only because you would limit the available air for the machine to use. Under the bed? Dust source supreme.

Step 1: Cut a hole in the box.

Obviously, you need a way for air to get into the box.

However, the machine is able to pull air through the air inlet on the back of the box though the air filters. If you look behind the filters, the hole is about 1 half inch diameter. Figure that as about 1/4 square inch area.

Unless you seal the box really well, it's probably going to let let air in with considerably less resistance than that. You also have to have a hole for the air hose and the power cord to go through. These holes have to be big enough to fit the connector on the end of the hose and cable, so they will have some spare space. If you're still worried, cut a 2 inch square hole in the far side of the box or just make the power cord hole that big.

If you're worried about heat, realize that the machine will be blowing 20 l/m of air through the hose, so it should cool fairly easily.

As for the Eustachian tube being open, are you talking about some abnormal condition? If I hold my nose and blow, I don't get any pressure in my ears until they pop a bit, and then they hold the pressure until it pops after that, so I presume my Eustachian tube isn't abnormally open.

I also noticed something I think you've said. The noise coming through the hose is a lot noisier if the water tank is full. I'll have to experiment with using it with no humidifier later.

[DocWils]

If you have yawned or coughed or any sort of thing under pressure (as in when using a CPAP), it can be that the Eustachian won't close 100% or more likely be at a higher pressure than before. Under both conditions, it is likely to conduct sound differently up the tube to the inner ear.

The PSR has a a daft tank design, same for the humidifier, and tank echo is higher than with the Resmed devices. Certainly than with the S9. Having used both machines, I was surprised at how much quieter the tank echo was from the S9 against the PSR, although both compressors are about the same in noise. The fine dust filter adds some noise to the PSR, as it makes the compressor work a bit harder. The amount of water in the tank on either device will alter the sound conduction of the tank, and the echo quality. Once the tank warms up, BTW, the echo dies down a lot until the tank is nearly empty, so preheating the tank is important in reducing the echo to some extent.

However, the best way to be sure it is the tank noise at all is simple - disconnect the humidifier and use the PSR without it - same sound? Also, different bores of tube will affect how sound is conducted up the tube - the narrower tubes work under another pressure, and change the sound conduction. Standard generic CPAP tubes will also conduct sound differently than heated tube sets, which are thicker and have heating coils in them, which reduce vibration of the tube membrane.

So many factors, eh? And yes, have a look at if you are clamping or grinding your teeth, as that will add to or ease bone conduction.