Find occurrences of sequences in sound wave

Question

I have quite basic knowledge of mathematics.

Consider two axis, time and dB (sound levels).

My question is if it's possible, using fourier or any other method, to find how many occurrences of specific dB values in a row exist.

For instance I want to find how many times the dB sequence 20,40,60 exists.

Sorry if I don't make sense !! :)

score 0 · Answer 1 · answered Nov 23 '13 at 22:23

0

You can just search through the file. Go through until you find a $20$, then see if it is followed by $40,60$ and count $1.$ If it isn't, go back to looking for $20$'s.

answered Nov 23 '13 at 22:23

Ross Millikan

374,822

I can not do that because it's time consuming. I tried it, but I cannot use it because of how long it takes. – Stefanos Kalantzis Nov 23 '13 at 22:34
I don't know how to use an FFT to do this. An FFT is of order $n \log n$, while this is of order $n$, so this will be faster. – Ross Millikan Nov 23 '13 at 22:36
I see... thanks ! – Stefanos Kalantzis Nov 23 '13 at 22:37
You should probably look at how you are reading the file and what language you are using. If it is three minutes of music sampled at 44 kHz, you have about 8 million entries. You can search that in seconds in Python and a fully complied language will be faster yet. – Ross Millikan Nov 23 '13 at 22:47

Find occurrences of sequences in sound wave

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