Unique low frequency mic.

Scooter B

Scooter B

New member
I am attaching a frequency response graph for a "microphone" that peaks between 300Hz and 700Hz with a rapid drop off after 700Hz.


For all intents and purposes it is a microphone but it was not designed for music recording applications.

Can you guess what it was designed for? (One hint it is a contact mic)

Could you think of any good uses for it in musical recording? :eek:
 

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Forget the Richter Scale, its how you accurately mic up an Earthquake or any other low rumbly force of nature.
 
Another excellent guess :D but not quite.

Another hint you can rule out industrial and environmental applications.

It was designed however to listen to something that "oscilates" normally at 1 to 1.67 Hz although the "oscilations" I am describing are not usually measured by the second but by the minute.

:confused:

;)
 
Scooter B said:
Another excellent guess :D but not quite.

Another hint you can rule out industrial and environmental applications.

It was designed however to listen to something that "oscilates" normally at 1 to 1.67 Hz although the "oscilations" I am describing are not usually measured by the second but by the minute.
Click to expand...

If it's by the minute then it's not hertz. Hertz = one cycle per second.

As low of you're describing would be infrasonic.

It was designed however to listen to something that "oscilates" normally at 1 to 1.67 Hz although the "oscilations" I am describing are not usually measured by the second but by the minute.

The mic in that graph wouldn't even come close to doing that.

Even at 1Hz the wavelength in air (m) is 343.98 . If you're saying one cycle per minute, the wavelength in air (m) is 20,638.8. That's a full 60 octaves below 1Hz.

That would be getting into the ultra infrasonic regions of planets and solar systems. Something I don't think a contact mic would come in to handy for. : )

My only guess would be something like earthquakes, volcanoes, storms, auroras or nuclear blasts. But if it's not for industrial or environmental sound measurements, then I'd have no clue.

But I think you've got some figures wrong somewhere. Maybe I do.
 
If it's by the minute then it's not hertz. Hertz = one cycle per second.
Click to expand...

The designated source itself oscilates at at 60-100 cycles per second but the sound produced as you have pointed out is not in that range.

If it's by the minute then it's not hertz. Hertz = one cycle per second.
Click to expand...

You are of course correct - I converted to Hz (cycles per second) from beats per minute. It was by design a vague hint to think in cycles per minute and not per second but perhaps misleading.



Even at 1Hz the wavelength in air (m) is 343.98 . If you're saying one cycle per minute, the wavelength in air (m) is 20,638.8. That's a full 60 octaves below 1Hz.
Click to expand...

Ah but the average speed of sound through soft human tissue is 1540 M/S divided by 100 Cycles/Sec then the wave lengs would be 15.4 meters.....stiff infrasonic but the full spectrum of sounds produced can be heard by a simple non amplified diaphragm.

I was kind of hoping Harvey would take a stab at it but I suppose I should end the suspense.....















Are you sure you want to know?















Attached is the otherside of the frequency graph. The text is in Japanese but the diagram for mic placement should explain it all.


This may actually use doppler at 1-2 KHz to pick up a doppler shift for the audio but I am not sure since I don't read Japanese.















:D
 

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Scooter B said:
I was kind of hoping Harvey would take a stab at it but I suppose I should end the suspense.....
Click to expand...
Scott,

I didn't realize you wanted me in this. There are a lot of ULF (ultra low frequency) transducers out there for use on shaker tables and vibration testing in general. If I knew it had a sticky side, I would have guessed something in the medical profession. If it had a screw hole or a bolt for attachment, it would probably be for vibration testing. (I'll bet they make one like that, too.)

Since this one has a sticky side, it might be interesting to attach it directly to a kick drum beater head, or a floor tom top head, and see how it mixes in with the other mics. Maybe try it on an upright bass or a piano sounding board.
 
So I guess this is to detect if the heart is beating and its rate and rhythm? An EKG monitor is used to do this in the modern day and age (post 1950's) as it also gives other important physiologic information about the heart's status. I suppose this might be useful in third world countries where all that was available to monitor a patient was an amplifier (radio, CD, tape player or other) that you could plug this in to. If you know of another use, please post.

Having designed, built and used an audio spectrum analyser for phonocardiographic studies in the 1970's, I'd have to say that the frequency response of this transducer for this purpose would be sorely lacking.
 
It was heading for the dumpster and I thought I would save it just to play around with...

It has a TRS cable but I am not sure what it would do to a preamp and if it might need phantom power.

If it infact used continuous wave Doppler it may be completely useless without a Doppler capable machine to transmit, recieve and measure the doppler shift.

We use Doppler signals in the range of 1.0 KHz to 2.5 KHz for cardiovascular blood flow measurement wich runs in the 0.3 M/s to 5 or more M/s. If you take the 1540 M/S for the average speed of sound in soft human tissue the Doppler shift is in the audible range.

I have thought about getting some cardiac Doppler samples from work to mess with in a DAW just for fun.

:)
 
That 2st response graph says something a bout a dresser, that's all I could make out for 3rd grade Japanese. Maybe some kinda furniture resonance test
dealio?
 
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