[Milsurplus] Throat Mike

[Mike Hanz]

I have the distinct impression that once the war began, the throat mikes 
had a short service life from a practical standpoint, Dennis.  Both the 
1946 NDRC report and an earlier NDRC pub dated 1 March 1943 ("Response 
Characteristics of Interphone Equipment") were not complimentary - 
probably because they had by then grabbed the sound engineers at Bell 
Labs, who introduced some measure of engineering analysis to the issue. 
  However, T.O. 16-1-29 (Handbook of Maintenance Instructions for 
Headsets and Microphones) is *really* helpful in answering your specific 
question on the T-30 - it sez "reasonably slow, clear, distinct speech 
is essential...  :-)  It does warn that placement of the elements should 
be symmetrical and "just above the Adam's apple."

J. Forster wrote:
 > The previous posts mirror my experience in the late 50's. I wonder if
 > an amplifier with a frequency response rising with frequency from
 > about 500 to 4000Hz would improve matters somewhat.

Excellent question, but spectrum shaping apparently would not help a lot 
- there is a mention in the NDRC report of a fundamental limitation of 
~1500Hz on the upper frequency limit of the skin insulated larynx, which 
was largely the cause of the intelligibility problem.  Thus the 2000Hz 
upper limit of the T-30 mike wasn't particularly effective in any case.

   - Mike

W7QHO@aol.com wrote:
> In a message dated 3/21/03 2:39:25 PM, AAF-Radio-1@cox.net writes (in   
> part):
> 
>>"9.2.3 Throat Microphones
>>
>>A device used widely by the USAAF at the beginning of WWII was the 
>>throat microphone.  In this assembly the microphone is strapped to the 
>>throat directly above the larynx.  Such an arrangement possessed the 
>>advantage of apparently low noise pickup and free use of hands, and it 
>>probably would have been a very effective instrument but for the fact 
>>that the speech signal available at the larynx is intrinsically 
>>unintelligible."
>>
> 
> Mike,
> 
> Can't argue with the above conclusion.   On the other hand, the device was 
> "widely used" reportedly.   If this is true, the users must have come up with 
> some techinque/trick to communicate with the things.   Or, maybe the guys 
> just took them off at the first opportunity?
> 
> Dennis D.   W7QHO
> Glendale, CA