[ntp:questions] measuring frequency

Terje Mathisen "terje.mathisen at tmsw.no" at ntp.org
Tue Feb 12 13:41:16 UTC 2013

robert bristow-johnson wrote:
> On 2/11/13 6:48 PM, unruh wrote:
>> ["Followup-To:" header set to comp.protocols.time.ntp.]
> why do that?
> hey guys, fix the Newsgroup: header here.
> On 2/11/13 6:48 PM, unruh wrote:
>  > ...
>  > Yes. However what you can do is to filter out the all but the strongest
>  > harmonic, and count which harmonic number it is.
> how do you know what the harmonic number is?  how would that information
> be determined in the general case.

This is what FFT was developed for, a single piano key will turn up as a 
somewhat smeared comb function, with peaks around the fundamental 
frequency plus the main harmonics.

Doing multiple FFTs should also show you any time-based change in pitch 
of the various peaks.


- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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