Not really, that will only work to find the frequency if the signal is a pure sine wave, maybe with some very quiet noise. If you know roughly the frequency where the sine wave is, it might still work if you put the signal through a very narrow bandpass filter first. Or it might not if the sine is too quiet compared to the rest of the audio.
-Ethan On Thu, Jan 11, 2018 at 12:16 PM, Benny Alexandar <ben.a...@outlook.com> wrote: > Hi Ethan, > > This looks interesting. Suppose I have a single tone sound getting mixed > with audio, > can we find that tone frequency and have an adaptive notch filter ? > > Does your above equation works in identifying a fixed frequency tone ? > For example by doing (x(t) + x(t-2)) / (2*x(t-1)) can we isolate a > single tone frequency ? > > -ben > > ------------------------------ > *From:* Ethan Fenn <et...@polyspectral.com> > *Sent:* Thursday, January 11, 2018 12:13 AM > *To:* Benny Alexandar > *Cc:* music-dsp@music.columbia.edu > > *Subject:* Re: [music-dsp] Finding discontinuity in a sine wave. > > Well, starting with the FIR filter I proposed, let's take this equality: > > 0 = x(t) - 2*C*x(t-1) + x(t-2) > > If we don't know exactly what our frequency is, we can solve for C: > > C = (x(t) + x(t-2)) / (2*x(t-1)) > > Of course we don't want to take just one computation of C, but if we do > some averaging and are careful about the singularity when x(t-1) is close > to 0, then we've got a simple adaptive notch. And we can get a running > estimate of the frequency by computing arccos(C). > > -Ethan > > > > On Wed, Jan 10, 2018 at 12:47 PM, Benny Alexandar <ben.a...@outlook.com> > wrote: > > This all works well in an ideal system. Suppose the sampling clock is > drifting slowly over period of time, > then the notch filter will fail to filter it. How to detect and correct > these clock drifts and have a stable notch filter. > > -ben > > ------------------------------ > *From:* music-dsp-boun...@music.columbia.edu < > music-dsp-boun...@music.columbia.edu> on behalf of Ethan Fenn < > et...@polyspectral.com> > *Sent:* Wednesday, January 10, 2018 10:33 PM > *To:* music-dsp@music.columbia.edu > *Subject:* Re: [music-dsp] Finding discontinuity in a sine wave. > > If the sine frequency is f and the sample rate is sr: > > Let C = cos(2*pi*f/sr) > > For each sample compute: > > y(t) = x(t) - 2*C*x(t-1) + x(t-2) > > y(t) should be 0 for every t... if not it indicates a discontinuity. This > is just an FIR filter with a zero at the given frequency. > > -Ethan > > > > > On Wed, Jan 10, 2018 at 11:58 AM, STEFFAN DIEDRICHSEN <sdiedrich...@me.com > > wrote: > > With any phase discontinuity, a spectral discontinuity is delivered for > free. So, the notch filter will have an output, a PPL would need to > re-sync, etc. > > Steffan > > > On 10.01.2018|KW2, at 17:51, Benny Alexandar <ben.a...@outlook.com> wrote: > > But if there is a phase discontinuity it will be hard to detect. > > > > _______________________________________________ > dupswapdrop: music-dsp mailing list > music-dsp@music.columbia.edu > https://lists.columbia.edu/mailman/listinfo/music-dsp > > > >
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