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4 votes

Time delay estimation of oscilloscope signals using cross correlation

As pichenettes indicated, in this case a peak at the middle of the output indicates 0 lag. The peak's offset from the middle point is your time lag. EDIT: It concerns me that the correlation is so n …
Jim Clay's user avatar
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2 votes
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determine background noise level via cross correlation

If you want to get an estimate of the noise, do the cross-correlation, and then multiply your transmitted sound by your cross-correlation peak and then subtract it from your received sounds. Make sur …
Jim Clay's user avatar
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2 votes

get amplitude difference via cross correlation?

You divide the peak of the correlation by the energy of $A$. $B$ is a scaled version of $A$, with some noise added to it. Thus, the equation for the cross-correlation peak is- $ A * B' = A * (kA' + …
Jim Clay's user avatar
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2 votes

When might looking at rising edges perform better than cross-correlation?

Using the rising edge is better than cross-correlation when there is the physical equivalent of an inductor in the system, which will introduce inertia into the system. That inertia will cause the ou …
Jim Clay's user avatar
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3 votes
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Normalized cross-correlation in detail

An individual inner product does produce a scalar, but often when a cross correlation is calculated multiple individual cross correlations (i.e. dot products) are calculated at different time offsets. …
Jim Clay's user avatar
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1 vote
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Cross-correlation peaks in acoustic multi-path conditions

I assume by "shift" you mean "shift in time". No, the first correlation peak should not be shifted in time, you should just get multiple peaks, assuming the time difference of arrival is not much sho …
Jim Clay's user avatar
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14 votes
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Is up-sampling prior to cross-correlation useless?

It's not cheating, and it's also not adding any new information. What you are doing is the same thing that any upsampling LPF is doing- adding zeros and then reconstructing the waveform with the alre …
Jim Clay's user avatar
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1 vote

Find the time lag for a wave

The time lag is equal to the index difference times the sample period. The sample period is: $$ T_s = \frac{1}{f_s} = \frac{1}{16000} = 62.5\mu s $$ Thus, the time lag from the first peak to the seco …
Jim Clay's user avatar
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3 votes

Ultrasound Signal Processing Methods

Cross correlation should work. I think the problem is the waveform that you are using. A square wave has bad auto-correlation properties. If it is a periodic square wave it will have multiple peaks …
Jim Clay's user avatar
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