| Author |
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Jerry Avins
Guest
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 Posted:
Mon Dec 05, 2005 12:19 am Post subject:
Echo suppression at Home Depot, or Ain't digital wonderful? |
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I had someone paged at Home Depot, and the clerk listened for a while at
the telephone, spoke the message into it, then hung up. Shortly, the
message came over the PA systems, loud and clear. That's a simple way to
eliminate all acoustic feedback. Had I thought of it, I would have
thought myself clever.
Jerry
--
Engineering is the art of making what you want from things you can get.
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ |
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Steve Underwood
Guest
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| Posted:
Mon Dec 05, 2005 1:16 am Post subject:
Re: Echo suppression at Home Depot, or Ain't digital wonderf |
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Eric Jacobsen wrote:
| Quote: | On Sun, 04 Dec 2005 13:19:44 -0500, Jerry Avins <jya@ieee.org> wrote:
I had someone paged at Home Depot, and the clerk listened for a while at
the telephone, spoke the message into it, then hung up. Shortly, the
message came over the PA systems, loud and clear. That's a simple way to
eliminate all acoustic feedback. Had I thought of it, I would have
thought myself clever.
Jerry
That's also common at airport gates nowadays. I think at the
airports it also makes certain that announcements from adjacent gates
don't overlap and garble each other, i.e., it'll wait until any
announcement from an adjacent gate is finished before playing the
current announcement.
At least, I think I've observed that behavior. ;)
|
I think you are right. I think the queuing requirement is the key reason
it is done, and not the acoustic feedback reason Jerry gave. We did
something like this about 10 years ago, and the main motivations were
queuing and editing. The user could use the DTMF keypad to restart
recording if they made a mistake, and to commit a correct recording when
they finished. Eliminating acoustic feedback seems a nice bonus, though.
Regards,
Steve |
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Eric Jacobsen
Guest
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| Posted:
Mon Dec 05, 2005 1:16 am Post subject:
Re: Echo suppression at Home Depot, or Ain't digital wonderf |
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On Sun, 04 Dec 2005 13:19:44 -0500, Jerry Avins <jya@ieee.org> wrote:
| Quote: | I had someone paged at Home Depot, and the clerk listened for a while at
the telephone, spoke the message into it, then hung up. Shortly, the
message came over the PA systems, loud and clear. That's a simple way to
eliminate all acoustic feedback. Had I thought of it, I would have
thought myself clever.
Jerry
|
That's also common at airport gates nowadays. I think at the
airports it also makes certain that announcements from adjacent gates
don't overlap and garble each other, i.e., it'll wait until any
announcement from an adjacent gate is finished before playing the
current announcement.
At least, I think I've observed that behavior. ;)
Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org |
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Jon Harris
Guest
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| Posted:
Mon Dec 05, 2005 9:16 am Post subject:
Re: Echo suppression at Home Depot, or Ain't digital wonderf |
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"Jerry Avins" <jya@ieee.org> wrote in message
news:EK6dnRG6TN_Yrg7eRVn-qQ@rcn.net...
| Quote: | I had someone paged at Home Depot, and the clerk listened for a while at the
telephone, spoke the message into it, then hung up. Shortly, the message came
over the PA systems, loud and clear. That's a simple way to eliminate all
acoustic feedback. Had I thought of it, I would have thought myself clever.
|
It's often called a "store and forward" paging system. Not only does it neatly
solve the problem of acoustic feedback, but also handles the issue of multiple
pages occurring simultaneously. With memory being cheap, it is quite practical
to implement as well.
--
Jon Harris
SPAM blocker in place:
Remove 99 (but leave 7) to reply |
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Raymund Hofmann
Guest
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| Posted:
Mon Dec 05, 2005 5:16 pm Post subject:
Re: Echo suppression at Home Depot, or Ain't digital wonderf |
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But isn't it much more challenging to suppress feedback than avoiding it
?
Especially in environments where the IR's are highly volatile ?
Raymund Hofmann
"Jerry Avins" <jya@ieee.org> schrieb im Newsbeitrag
news:EK6dnRG6TN_Yrg7eRVn-qQ@rcn.net...
| Quote: | I had someone paged at Home Depot, and the clerk listened for a while
at the telephone, spoke the message into it, then hung up. Shortly, the
message came over the PA systems, loud and clear. That's a simple way
to eliminate all acoustic feedback. Had I thought of it, I would have
thought myself clever.
Jerry
--
Engineering is the art of making what you want from things you can
get.
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ |
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Matt Timmermans
Guest
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| Posted:
Thu Dec 08, 2005 8:47 am Post subject:
Re: Echo suppression at Home Depot, or Ain't digital wonderf |
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"Jerry Avins" <jya@ieee.org> wrote in message
news:EK6dnRG6TN_Yrg7eRVn-qQ@rcn.net...
| Quote: | I had someone paged at Home Depot, and the clerk listened for a while at
the telephone, spoke the message into it, then hung up. Shortly, the
message came over the PA systems, loud and clear. That's a simple way to
eliminate all acoustic feedback. Had I thought of it, I would have thought
myself clever.
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That reminds me of a very clever radio module I saw a while ago. I wish I
could remember the manufacturer...
In any case, the receiver section used 2 high gain amplifier stages, and
feedback was avoided like this:
1) Stage one turns on for, say 1ms, amplifies the received signal, sends it
through a SAW delay, and then TURNS OFF.
2) Stage two comes on for 1ms just in time to catch the signal coming out of
the delay, amplifies it for processing, and then TURNS OFF.
3) repeat.
Of course, you only get 1ms snippets of signal, but that was just fine for
the target application.
--
Matt |
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