🚀 go-pugleaf

In article <414@gtx.com>, al@gtx.com (0732) writes:
> One often hears about people blowing whistles or air horns into a
> telephone to thwart obscene callers. Is a telephone capable of
> transmitting enough sound amplitude to cause pain or damage to the
ears?
> If so, this seems to be a dangerous capability in the hands of some
crank.

Larry Lippmann responds:

>	...it  is  improbable that sufficient acoustic  energy  (sound 
>pressure  level in dB) could be created such that physiological injury
>would occur.
>
>       ...As a combination EE/biochemist with a multidisciplinary
>background,  I have done some forensic science consulting for a number
>of  years.   About ten years ago,  I was retained as a consultant in a
>workmen's  compensation case.   It seems that a middle-aged woman  who
>had worked as a switchboard operator for 20-some years had applied for
>compensation  resulting  from partial hearing loss in  one  ear.   Her
>allegation  was  that then presence of clicks and loud noises  in  her
>"headset  ear" over many years caused her hearing loss.   My  function
>was to work with an otolaryngologist to disprove her claim.
>
>     My first reaction was that there was insufficient sound  pressure
>level to cause such injury.  However, I learned that for the past five
>years  the woman used a Plantronics miniature headset (the kind with a
>flexible  plastic ear tube).   Now with such a headset,  there was  an
>almost  perfect sound conduction between the receiver element and  the
>ear.    So,   we  contacted  Plantronics  and  got  some   engineering
>information.   We  got  a sample headset and conducted our  own  sound
>pressure  measurements  using a Bruel & Kjaer "artificial  ear".   The
>conclusion  was that the maximum sound pressure level which  could  be
>experienced  through  this  headset in a switchboard  environment  was
>still  insufficent (by generally accepted medical criteria)  to  cause
>hearing impairment.
>
>     But  the  use of a receiver with a plastic ear tube did  make  me
>seriously consider the possibility of injury.


The  big danger of plastic ear tubes,  as in Plantronics headsets,  is 
transmission of ear infection if headsets are shared.   Wearing such a 
device,  even  if  clean,  for long periods might  help  incubate  ear 
infections.  Plantronics' latest models use a lightweight conventional 
external earphone instead of the ear tube.

I  like Plantronics headsets,  especially the old model MS-50 with the 
headband  (as  worn  upside-down by Clint  Eastwood  in  the  airplane 
hijacking  scene in "Dirty Harry").   Plantronics headsets  configured 
for  telephone  service  are  available for $10  to  $20  at  hamfests 
(regional  gatherings  of  ham  radio  operators).   They  are  easily 
modified  for  radio service;  I use them while flying,  and  with  my 
mobile and handheld ham rigs.   I also have a custom-made hard plastic 
earmold  with an external bar for mounting the MS-50,  and a  flexible 
tube  to connect to the earphone output.   It's very comfortable,  and 
ideal  for emergency service and high-noise environments.   (Kits  are
available for making your own ear impression,  which is mailed back to 
the company which makes the finished product.)

reference:
----------
Reid,  F.  "Using  Simulated  Carbon Microphones with  Amateur  Trans-
mitters"  _Ham Radio_ magazine, Oct. 1981 p. 18.

--

Frank Reid
PO Box 5283
Bloomington, IN 47402
reid@gold.bacs.indiana.edu