Throat Microphone with earphone
I have been on the lookout for a throat microphone that really works . I did
have what I would call a good one but the factory went out of production. I
wished Id stocked up on more of them , after much importation of many brands and
testing with dismal results , I have come across one that actually
performs very well. There are basically two types. piezo electric and electret .
Piezo electric us a small thin ceramic disc 10-20mm diameter which is silver
plated on each side, this disc is held firmly at the periphery and has a small
spring that connects the center of the piezo disc to the thin flat
plastic diaphragm that rests against the users skin. vibrations in the
diaphragm travel through the connecting spring to induce voltage across the
silvered sides of the piezo disc. The high impedance electrical output of
the vibrating piezo disc is transformed to a much lower operating impedance by a
single transistor stage , hence like the electret based throat mic , the piezo
too requires a few milliamps of current at a few volts to work. Piezo
electric throat mics tend to have a higher frequency spectra output with not so
many low frequencies , however they tend to have a narrower more peaky frequency
response, no doubt related to physical resonance properties of the piezo
element so they can sound quite tinny and un natural , I have only found
one brand of piezo based throat mics that puts out what I would call adequate
communications quality audio.
This unit However is electret mic based, the mic is in a pressure chamber
that sits against the neck , there is a sealed chamber under the large skin
contact diaphragm and the much smaller electret mic diaphragm , this sealed
chamber acts much like a "pneumatic" diaphragm movement
amplifier . Hence small movements of the throat skin diaphragm cause a
much larger movement in the electret diaphragm in the ratio of their surface
areas. Electret mics have a very flat frequency hence this mic has quite a
flat output. The throat tends to attenuate a lot of the high
frequencies more so than the low frequencies, I guess the speech is
formed at the lips and tongue so has to travel back down the throat or
though the flesh .
This mic has a small single earbud type earphone on a length of thin
fexible cable , the earphone can be worn under a ear defender if necessary and
not destroy the acoustic isolation , The cable has a PTT button in series with
the electret mic with a provision to switch the PTT permanently on , the mic and
speaker are terminated in a 2.5mm stereo plug and 3.5mm mono plug
respectively
picture in here
price NZ$80 plus postage
Pinfold Health Services Ltd,1172 Arawa St, Rotorua 3201,New Zealand. ph +64-7-3488850 fax +64-7-3486555 pinfold@xtra.co.nz