[BC] Headphone polarity and bone conduction...

[Ron Cole]

That's all true for a local headsets.  Many consoles had phase reversal
switches that are their to compensate for mis wired mics in a multiple
microphone mix but can be used to flip the phase of the headphone audio as
well..

In the On Air monitoring case I allays figured that since the on air audio
chain had phase scramblers in it there would be no phase correlation back to
the headsets.

It was a stab in the dark to eliminate a problem that the one announcer had
and we solved to problem.  The rest of the staff could not tell any
difference in the off air audio in there cans.

Of course this has to be like 15 years ago since I left full time broadcast
engineering over 10 years ago.


Ron
N5HYH


On 8/13/06, Burt I. Weiner <biwa at earthlink.net> wrote:
>
> Actually, what you had here was a classic case of cancellation or
> partial cancellation due to phase shift.  The voice was arriving from
> two separate sources and acoustically mixing in the ear.  One path
> was from the earphone transducer itself and the other path was via
> bone (and other stuffs in the head) conduction.  By reversing the
> polarity of the audio arriving in the headphones you brought them
> back into phase or at least, less out-of-phase.
>
> A test you can do is to put on the headphones, open the mic channel
> (in audition) and say "Oooooooooooooooooooooooooooooooooh".  As you
> do, turn the headphone volume up and down.  If they are out of phase
> with the bone conduction you will hear the volume go through a
> null.  Not a deep null, but a an obvious null that is typically in
> the lower mid range.  This can cause the talent to claim they don't
> have enough earphone volume and try to turn things up to the point of
> distortion.
>
> On my remote gear I have a switch for headphone polarity that I can
> flip to correct the problem when it arises.
>
> Burt
>
> At 03:40 PM 8/13/2006, you wrote:
> >From: "Ron Cole" <rondcole at gmail.com>
> >Subject: Re: [BC] Absolute Polarity (was XLR pinout debate)
> >To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
> >Message-ID:
> >         <2f88e090608131036w19c0cb2ek6e1259dccb98b426 at mail.gmail.com>
> >Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> >
> >In the pre digital days, I had an jock that was constantly complaining
> about
> >the off air sound of the headphones.  I could never find anything wrong
> with
> >the off air audio feed then one day I swapped the balanced audio polarity
> >and She quit complaining.  I guess she was sensitive to "absolute
> polarity"
> >of the whole transmission path.
> >That was not an issue after the Digital STL was installed, too much delay
> to
> >listen live any more.
> >
> >Ron
>
> Burt I. Weiner Associates
> Broadcast Technical Services
> Glendale, California  U.S.A.
> biwa at earthlink.net
> K6OQK
>
>
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