Re: algorithms for location versus for frequency?

Ron N. wrote:

I suppose all characterization of signals inside some buffer
of samples is a form of statistical signal processing.

When asking about the frequency of some signal in comp.dsp,
all sorts of algorithms are mentioned, forms of autocorrelation
(or squared difference, etc.), or fft/dft usage (windowed, zero
padded, phase differentiated, etc.). Also, there seem to be lots
of textbooks on these forms of analysis in the local libraries.
Very little mention of statistical techniques from old radar/sonar
textbooks.

From what I've seen in sonar, the older techniques for frequency
estimation needed improvement.

However when asking about how to find the location of a signal
(start/stop/center position), I often get pointers to some signal
processing textbooks (of which I haven't found any in the local
library yet).

Why this difference? Is location analysis less tractable, less
interesting, or less explainable in comp.dsp algorithms, than
is frequency?

"Location analysis", if you know the signal you're looking for, could
be thought of as a variation of matched filtering (though there is no
synchronization in the location problem).

Perhaps a better (well, more used) name is "detection" rather than
"location"?

In some of the sonar problems I've looked at, you're usually interested
in "track initiation" and "loss of track" (i.e. the beginning and end
of something of interest). Track initiation is generally a detection
problem. Loss of track can be harder, especially if the one signal
drops in an out of the noise.

For instance, what means could be used to measure the precise
duration (within rise time uncertainty) of a DTMF tone, Morse
code dit, or saxaphone note from a buffer of sound samples?

Goertzel will do the DTMF tone detection.

Ciao,

Peter K.

.

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