# Low and High Frequencies



## cointosser13 (Dec 27, 2013)

I just got a better Stethoscope, a Lightweight II S.E. In the booklet it's talking about low and high frequencies with the tunable diaphragm . What are they talking about when they say that? while in the ambulance when does low and high frequencies matter?


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## Aprz (Dec 28, 2013)

Different sounds may have a low or high frequency, and the side you use or the pressure you exert may be better for hearing those particular frequencies.

Examples of low frequency sounds are Korotkoff sounds when taking a blood pressure, bowel sounds, and heart tones/murmurs during cardiac auscultation.

An example of high frequency sound is breath sounds when auscultation the lungs.

It depends on the stethoscope, but typically the bell (usually smaller, commonly mistakenly called "the pediatric side") is better for low frequency sounds and the diaphragm (usually the larger side) is better for high frequency sounds. A lot of expensive stethoscopes like Littman have tuneable diaphragm that can change from high or low frequency by the pressure you exert when applying the diaphragm to the patient (low pressure is low frequency, high pressure is high frequency).

AHA recommends using the bell (for low frequency), when taking a blood pressure, however, few actually do it this way. 

Does it really make a difference? In my opinion, no.


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## mycrofft (Dec 28, 2013)

Aprz said:


> Different sounds may have a low or high frequency, and the side you use or the pressure you exert may be better for hearing those particular frequencies.
> 
> Examples of low frequency sounds are Korotkoff sounds when taking a blood pressure, bowel sounds, and heart tones/murmurs during cardiac auscultation.
> 
> ...



Money shot.


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## unleashedfury (Dec 28, 2013)

Aprz said:


> It depends on the stethoscope, but typically the bell (usually smaller, commonly mistakenly called "the pediatric side") is better for low frequency sounds and the diaphragm (usually the larger side) is better for high frequency sounds. A lot of expensive stethoscopes like* Littman have tuneable diaphragm that can change from high or low frequency by the pressure you exert when applying the diaphragm to the patient (low pressure is low frequency, high pressure is high frequency).*
> 
> AHA recommends using the bell (for low frequency), when taking a blood pressure, however, few actually do it this way.
> 
> Does it really make a difference? In my opinion, no.



I haven't noticed a difference either when using opposing ends of the stethoscope. 

and this whole low pressure high pressure tuneable diaphragm hoopla. I think its just too much of a PITA to figure out. I put scope where I need to, to hear what I need to. If I can't get a good sound I reposition and try again.


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## Aprz (Dec 28, 2013)

unleashedfury said:


> I haven't noticed a difference either when using opposing ends of the stethoscope.
> 
> and this whole low pressure high pressure tuneable diaphragm hoopla. I think its just too much of a PITA to figure out. I put scope where I need to, to hear what I need to. If I can't get a good sound I reposition and try again.


Maybe you are using both sides of a tuneable diaphragm rather than one that has a bell for low frequency and diaphragm for high frequency? I'm kidding.  I personally don't notice a difference either. Some people have told me they do after I tell 'em about it, but I think it's kinda a placebo "Oh, wow, it's way louder when I auscultate the blood pressure with the bell!"


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## unleashedfury (Dec 28, 2013)

Aprz said:


> Maybe you are using both sides of a tuneable diaphragm rather than one that has a bell for low frequency and diaphragm for high frequency? I'm kidding.  I personally don't notice a difference either. Some people have told me they do after I tell 'em about it, but I think it's kinda a placebo "Oh, wow, it's way louder when I auscultate the blood pressure with the bell!"



Maybe we should do a random blinded study, on new EMT students using the bell vs. the diaphragm


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## NPO (Jan 10, 2014)

unleashedfury said:


> Maybe we should do a random blinded study, on new EMT students using the bell vs. the diaphragm



The new semester is starting. I'll bring it up with the new EMT students.


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