snore sensors

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snore sensors

Postby tidegirl » Wed Oct 28, 2009 7:55 am

Does anyone know what the difference is between a snore sensor and a snore microphone? I am looking for equipment in MVAP, and they have both listed. Same companies too, so it isn't just a different name. Also, do you know which is better?
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Postby thesleepwhisperer » Wed Oct 28, 2009 8:06 am

We use them both. The snore mics give decent signals but we have found that they don't pick up the signals as well as the snore sensors. I like using the snore mics on our pts with the thicker necked pts...too many folds to deal with.
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Postby somnonaut » Wed Oct 28, 2009 8:51 am

AFAIK
A microphone is just that, it has a dynamic range of sound detection
A snore sensor is usually based on piezo crystal technology which yields a signal when movement is detected. It implies sound, through neck movement, not be sensitive to sound directly.
To test: if you hold the microphone 1 foot from your mouth and shout at it, it will pick up a signal
vs.
Holding the snore sensor 1 ft from your mouth and shout at it, it does not since it does not come in contact with movement (the air is not dense enough to displace the surface of the sensor, place pressure on the crystal, and the crystal create a voltage.

http://en.wikipedia.org/wiki/Piezoelectricity
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Postby slowdavesleep » Wed Oct 28, 2009 11:47 am

Actually both the sensor and the microphone would likely be piezo, to the best of my knowledge. From the wikipedia page you linked :

"Detection of pressure variations in the form of sound is the most common sensor application, e.g. piezoelectric microphones (sound waves bend the piezoelectric material, creating a changing voltage) and piezoelectric pickups for Acoustic-electric guitars. A piezo sensor attached to the body of an instrument is known as a contact microphone."
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Postby linuxgeek » Wed Oct 28, 2009 5:27 pm

I was gonna say the same thing. It's essentially a contact microphone.

My guess is that if you took all the insulating material off the snore sensor and did that 1 foot test, it would be sensitive to air movement as well.

I've played with piezo material that is pretty sensitive to air movement.

Try converting your snore sensor signal to audio (EDF to WAV) sometime and listen to the patient talking. It's very muffled, but that's partially cause we have very low sample rates for capturing audio.
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Postby somnonaut » Wed Oct 28, 2009 11:09 pm

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Postby linuxgeek » Thu Oct 29, 2009 12:42 am

somnonaut wrote:Not all mics are piezo.
http://en.wikipedia.org/wiki/Microphone


That's right, I think most music recording mics are NOT piezo.
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Postby Rick » Fri Oct 30, 2009 10:19 pm

If I might, since I work at a sensor manufacturer, gnerally most of this has been right: snore sensors are piezo elements and microphones are, well, microphones. There are electret microphones which require a power source to work, these would be on equipment like the Alice 3& 4, maybe the SD20. Other systems would have a dynamic microphone that produces sound by a coil and diaphragm.
The biggest difference I have seen between sensors and microphones is that the sensors can tend to be a bit more noisy with elevated baselines requiring heavy filtering and the microphones have quiter baselines.
Oh, BTW, there are dynamic microphones that are encased (in blue and gold plastic) which will not pick up ambient sound because it is covered, the plastic must be vibrated to produce a signal, that protects the fragile element of the microphone.
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snore mic vs snore sensor

Postby RBonato » Sat Oct 31, 2009 12:44 pm

Yes, Rick is correct and I'll add some of my thoughts. Snore sensors are typically piezo discs in this industry encased in some type of hypoallergenic plastic because you need to affix them to the body close to the source of snoring at the upper airway. When placed on the neck they respond to vibrations in the tissue associated with snoring and when filtered and amplified by the PSG system you get the characteristic waxing and waning signal appearance of snoring. On occasion tissues of the upper airway will interfere with the ability of the sensor to detect vibration. Placement is also vital.

A snore microphone attached to the body and used for sleep recordings is usually an electret condenser microphone with an external DC power source. If attached to the body you really don't want to have something plugged into a 120-volt AC wall outlet unless you have medical grade power isolation. Hence, the external power supplied by a battery. Positioning is key. You could hang a mic from the ceiling or affix one to the headboard of the bed, but then the signal strength will vary according to body position during sleep. Some colleagues from France told me about 15 years ago that they place their snore microphones on the nasion because they are interested in snoring volume and in this manner the microphone is at a constant distance from source of snoring regardless of body position. BTW, if you are placing a snore microphone on the neck and aren't looking for snore volume, you aren't really focusing on a valuable clinical measurement.

Which one to use? Personally, I prefer a snore microphone over a snore sensor (and yes, like Rick, our company makes both), but I should emphasize my preference is to actually digitize and record snoring volume. As a purist, my preference is to directly record the signals of interest. Snoring is a complaint of unwanted noise from a bedpartner and to quote Dr. Guilleminault of Stanford, "Snoring is like an alarm telling you there is something wrong with breathing during sleep." Looking at waxing and waning signals inferring snoring isn't a direct measurement. I have always found a properly placed EMG electrode on the chin and one slightly beneath it (i.e., mentalis - submentalis placement) would always give me the waxing and waning signal indicative of snoring similar in appearance obtained from a snore sensor (as a aside, it also virtually negates unwanted EKG artifact newbies post about elsewhere in this form). I confirmed this over 1,000 PSG from 1988 to 1995 because I also had audio and could hear and watch simultaneously. So I was able to get the same snore sensor signal from a couple well prepped and placed EMG electrodes. But my challenge remained wanting to record the signal of interest: snoring volume. This signal isn't the number of snores on the screen, which you get with either a chin EMG recording, a snore sensor, or a snore microphone placed on the neck or if you aren't recording volume. But imagine the clinical value of actually recording the snore volume and displaying it within your split-night PSG reports. I created a Snore dB table on my Sandman system back in '95 and to this day I find snoring volume during baseline and treatment an extremely valuable piece of information. As an example, I attach a case study where I did two tests on July 1/09 and July 3/09 on a 73-year old. You can see the dramatic drop in snoring and improvement in other clinical parameters therein.

Circling back to 1995, off-the-shelf technology exists today for sleep technologists to record snoring volume for accurate diagnosis and to monitor treatment effectiveness. As perhaps the mildest form of SDB, it remains our responsibility as sleep professionals to take snoring very seriously and to provide relief for this condition. Approximately 50% of the general population snores. About 20 to 25% of couples in North America don't sleep together (I suspect half really don't want to!) and the number one complaint from a bedpartner remains snoring.
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Postby somnonaut » Sat Oct 31, 2009 3:28 pm

Nice Rick and Rick (hey, hey)

RB, what about volume per sleep stage? Any report for that? Would buy 8 off the shelf units that calibrated the sound and then entered the dB voltage into a DC input of my PSG (hint, hint) so that I would not have to keep asking the same from CNS, Rembrandt , now Compumedics. Oy.
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snoring volume by sleep stage

Postby RBonato » Sun Nov 01, 2009 1:05 pm

Somno,

To get dB volume by sleep stage you would need to modify the reports within the PSG system to calculate such a table in a similar manner to how PSG systems produce an SpO2 table, or an ETCO2 table. Inputting the Q-Snor dB volume as a DC signal into the PSG system should permit generating such a table. The signal range is from 0.4V to 1.0V (specifically using a Q-Snor system) which corresponds to a dB level of 40 to 100. If you mount the mic on the headboard or from the ceiling there is no patient contact and I suspect the dB volume sensor would last virtually forever. But placement on the nasion has some advantages as I mentioned in my earlier post.

From a purely clinical outcomes perspective, my preference is more a baseline versus treatment comparison, and I am less interested in sleep stage differences, per se. For patients with an AHI of 6.5 we're already close to the floor for improving the index, but there is often plenty of room to quantify and document an improvement in snoring volume. The bedpartner really doesn't care if most snoring occurs during REM sleep - they just want it fixed and the snoring human needs it fixed for obvious reasons.
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Postby somnonaut » Sun Nov 01, 2009 2:48 pm

RB,
Yes, I realize the sleep tabulation comes down to the staging software being used. I was a little tongue in cheek since the Nap-Pap thread talks of assessing sleep via snore mic. But I was not clear enough.

The Q-snor seems like it hits the mark.
http://braebon.com/guides/0544.pdf

Hmmm, now I have to free up a DC input on my E-series or wait for my new Gr..... Oh sorry I am not allowed to speak its name.
Please PM me purchase price. Or have whoever contact me for pricing.
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Re: snore sensors

Postby RayMeece » Thu Jun 07, 2018 10:42 am

Thomasee wrote:I trashed the clip ons and ordered teh Nonin flex reusable ones...
[url="https://sinokmed.com/collections/reusable-spo2-sensors"]spo2 sensor[/url]


You talking SaO2 sensors, and this thread is about SNORE sensors.

That said, the flex ones are definitely the way to go.
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