Audio Delay Circuit

[George W]

I have a need to measure the relative delay between two audio signals
arriving at a receiver via different paths. The audio signals are standard
3 kHz audio bandwidths containing voice or music. One could arrive as much
as 1 msec before or after the other. I'd like to be able to measure the
difference in time of arrival between the two signals down to 1 usec if
that's possible.

Any suggestions? I'm thinking of using a 180 degree phase shifter and
adjusting a variable delay line for a null when the signals are summed.

Thanks.

George

 

[Tam/WB2TT]

"George W" <look@signature_to.reply> wrote in message
news:AVFfd.3690$kM.3279@newsread3.news.pas.earthlink.net...

I have a need to measure the relative delay between two audio signals
arriving at a receiver via different paths. The audio signals are
standard
3 kHz audio bandwidths containing voice or music. One could arrive as
much
as 1 msec before or after the other. I'd like to be able to measure the
difference in time of arrival between the two signals down to 1 usec if
that's possible.

Any suggestions? I'm thinking of using a 180 degree phase shifter and
adjusting a variable delay line for a null when the signals are summed.

Thanks.

George


How about limiting each signal, and using a counter in time interval mode to

measure A - B or B - A. Most counters would give 100 ns resolution. You
might also have to bandlimit each signal to BW < 1KHz on each channel prior
to the limiters.

Tam

Tam

 

[Paul Hovnanian P.E.]

Robert wrote:

Hell use a Scope, dual channel no problem.

Hmm. A 3 kHz signal with -1 to +1 ms delay. At 3 kHz, that's 6 cycles
with no way of knowing which peaks correlate. For a modulated signal,
correlation might be easier to determine, but for something like audio
(speech for example), that might be difficult to follow on a scope.

Even a DSP correlator could match the wrong peaks if the modulation
didn't have enough frequency components to make the solution unique. A
longer sampling window will minimize this problem.

--
Paul Hovnanian mailtoaul@Hovnanian.com
------------------------------------------------------------------
Hit any user to continue.

 

[Mac]

On Wed, 27 Oct 2004 21:55:40 -0700, Paul Hovnanian P.E. wrote:

Robert wrote:

Hell use a Scope, dual channel no problem.

Hmm. A 3 kHz signal with -1 to +1 ms delay. At 3 kHz, that's 6 cycles
with no way of knowing which peaks correlate. For a modulated signal,
correlation might be easier to determine, but for something like audio
(speech for example), that might be difficult to follow on a scope.

Even a DSP correlator could match the wrong peaks if the modulation
didn't have enough frequency components to make the solution unique. A
longer sampling window will minimize this problem.

The OP said voice or music. I would not expect there to be any problem
correlating this in a DSP, although I have never done it. I actually think
that it would be easy on a scope, too (I have looked at music on a scope),
but if that's the kind of solution that was wanted, why ask on s.e.d?

--Mac

 

[Tam/WB2TT]

"Robert" <RB@comcast.net> wrote in message
news:x0Rfd.316233$MQ5.22266@attbi_s52...

Hell use a Scope, dual channel no problem.

Done that. I felt he wanted something more sophisticated.

Tam

"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
news:i--dnTn0yq3dAeLcRVn-pQ@comcast.com...

"George W" <look@signature_to.reply> wrote in message
news:AVFfd.3690$kM.3279@newsread3.news.pas.earthlink.net...
I have a need to measure the relative delay between two audio signals
arriving at a receiver via different paths. The audio signals are
standard
3 kHz audio bandwidths containing voice or music. One could arrive as
much
as 1 msec before or after the other. I'd like to be able to measure
the
difference in time of arrival between the two signals down to 1 usec if
that's possible.

Any suggestions? I'm thinking of using a 180 degree phase shifter and
adjusting a variable delay line for a null when the signals are summed.

Thanks.

George


How about limiting each signal, and using a counter in time interval mode
to
measure A - B or B - A. Most counters would give 100 ns resolution. You
might also have to bandlimit each signal to BW < 1KHz on each channel
prior
to the limiters.

Tam