FFT spectrum graph missing harmonics

I ran a perfect tone spectrum analysis, and saw no harmonics, which is the right result.
i then clipped that tone 3 dB using the amplify effect, but no harmonics appeared on the spectrum graph.
how can i fix this?

Increase the Size number in the Spectrum tool. There is no optimum setting. Too high and your information gets lost in a blizzard of spikes. Too low and it misses some significant data.

Also, pull the spectrum window larger. Koz

I clipped a 440 Hz tone 3 dB, and the waveform showed correctly with the expected flat tops.
The Spectrum tool used a 4.5 Gaussian window.
the size was as high as it would go.
there are no harmonics visible on the spectrum plot except for the fundamental.
The lower limit of the plot was -84 dB.
I know that the beginning harmonics of a tone clipped 3 dB are much higher than -84 dB.
what gives? I tried all the windows, and none provided a useful plot to determine the relative height of the harmonics.

I just tried that and I go a whole forest of spikes.

You are drag-selecting a portion of the damages blue waves, right?

I’m not on my home machine, so I can’t do illustrations.


Are you working with a bit Format that really Clips the Sound? (24 or 16 bit)
What happens if you enter one of the two clipping lines in the Nyquist prompt?

(Clip s 1)
;; or with a sine:
(Clip (scale-db 3 (osc (hz-to-step 440))) 1)

Good point. I did it with Effect > Hard Limiter. How did you do it? You can’t do it by smashing Audacity Headroom. Audacity doesn’t have natural headroom clipping.


hard limiter is not an option in my list of effects.
is it located under one of the other effects?
am i missing a download?
my tone only runs for 1.0 second. does it need to be longer?
rev 2.0.3

It’s a plug-in effect. There are hundreds of plug-ins available for Audacity (http://audacityteam.org/download/plugins) though personally I’d not recommend installing more plug-ins than you need as the Effect menu can quickly become very cluttered,

You can easily clip audio using the “Nyquist Prompt” effect.
Select the track, open the Nyquist Prompt and copy/paste the following code:

(clip s 0.5)

This will clip the selected sound at a level of 0.5 (half the track height).

clip s works great.
where can i find a list of these commands?

There are some examples here: http://wiki.audacityteam.org/wiki/Nyquist_Audio_Programming

The full Nyquist manual is here: http://www.cs.cmu.edu/~rbd/doc/nyquist/
and some information about creating Nyquist plug-ins for Audacity: http://wiki.audacityteam.org/wiki/Nyquist_Plug-ins_Reference

If you have questions about Nyquist, we have a forum board here: http://forum.audacityteam.org/viewforum.php?f=39