Hi Annabelle
How did you arrive at those frequency values?
From what I've measured so far is the signal's fundamental frequency 171 Hz.
This gives511 Hz and 684 Hz as harmonics 3 and 4.
(I've adjusted that to 172 HZ below to get nearer to your frequencies)
In other words, the following code uses only one tone but with
different weights for the partials.
Since the fundamental is deeper, the chirp will only rise to 172 Hz
but 516 Hz and 688 Hz will be prominent.
The noise sound is just a frequency modulation to make the signal less sterile.
You can change the value 0.3 to something else whereby 0.0 means no
modulation and 1.0 means 172 Hz max. deviation (although it is much
less due to the high pass filter).
The integer numbers of the frequency-envelope after *sound-srate* mean seconds.
The question of aliasing does actually not arise since I've only used
harmonics up to 8000 Hz.
Cheers
Robert
Code for the Nyquist prompt:
(setf amplitudes '(-25.3 -29.4 -33.9 -34.5 -37 -39.4 -39 -39.4 -38.6
-40.8 -41.6 -41.7 -41.8 -41.7 -43 -43.8 -44.4 -43.5 -44.7 -45 -45.2
-45.8 -47.4 -47 -47.1 -46.6 -48.4 -47.7 -47.6 -48.3 -48 -48.1 -49.1
-49.4 -49.2 -49.2 -48.6 -50.3 -50.4 -50.1 -50.8 -50.8 -51.1 -51.3
-50.7 -51.2 -51 -52 -51.9 -51.7 -52.8 -52.7 -53.9 -53.9 -54.4 -53.6
-53.7 -54.9 -54.8 -54.7 -55.5 -55.7 -56.5 -55.6 -55.7 -56.6 -57.4
-57.3 -56.7 -57.1 -57 -57.4 -57.8 -58.4 -58.5 -58.3 -58.2 -58 -58.3
-58.3 -57.7 -58.7 -59.2 -58.7 -59.3 -58.7 -59.2 -59.1 -58.6 -59.5
-58.6 -59.4 -59.4 -60 -60.5 -59.6 -60 -59.7 -60.4 -59.9 -59.9 -60.5
-59.9 -61 -61.4 -61.2 -61.2 -60.9 -61 -60.9 -60.9 -61.2 -61.1 -60.5
-61 -61.4 -60.7 -61.1 -61.1 -61.2 -61 -61.1 -61.1 -60.8 -62.1 -61.9
-62 -61.6 -62 -62.2 -61.7 -62.3 -61.9 -61.5 -62.2 -62 -61.5 -61.6
-61.9 -62.5 -61.9 -63.1 -62.9 -63.2 -63.2 -63.4 -62.9 -62.6 -62.7
-63.2 -62.8 -63.3 -62.8 -63.1 -63 -63.2 -63.1 -63.3 -63 -62.8 -62.6
-63.5 -63.4 -63.3 -62.8 -63.5 -63.4 -63.9 -63.9 -64.4 -64.3 -64.3
-64.4 -63.8 -64.2 -64.1 -63.6 -64.3 -63.7 -64.4 -63.6 -64.5 -63.9
-64.3 -63.5 -63.8 -64.1 -63.5 -64.3 -64 -64.1 -63.9 -64 -64.3 -65.3
-64.7 -65 -64.7 -64.6 -65.4 -64.9 -65.2 -64.6 -65.1 -65.4 -65.5 -64.6
-65.2 -65 -65.4 -64.8 -65.1 -65.3 -64.5 -65.1 -65.2 -64.5 -65.2 -65.5
-65.3 -64.8 -65 -64.7 -64.6 -65.1 -64.9 -66.3 -66.2 -66.2 -65.8 -65.8
-66 -66.2 -65.8 -65.7 -65.7 -66.4 -66.4 -66.2 -66.2 -65.9 -66.3 -66.1
-65.7 -66.3 -66.2 -66.1 -65.9 -66.2 -66.1 -65.6 -66.5 -65.6 -65.5
-66.1 -67.2 -67.3 -66.8 -67.3 -67 -66.7 -67.1 -67.3 -67.1 -67.2 -66.7
-66.7 -66.7 -67.2 -67 -66.8 -67.4 -67.3 -66.8 -67.1 -66.8 -67.4 -67
-66.7 -66.7 -66.8 -67.1 -67.3 -66.8 -67.4 -66.5 -67.4 -66.6 -67.1
-66.9 -66.6 -67 -67.5 -66.7 -67 -67.2 -66.6 -67.3 -67.5))
(setf harmonics '(4 3 2.96 3.95 9 5 7 8 16.01 7.93 7.95 8.89 15.8
15.99 15.81 7.91 11.86 15.01 6 7.98 12 8.98 4.94 6.91 14.81 20.01 11
14.82 14.99 15.87 15.97 21.01 4.96 6.94 8.95 15.85 15.96 14.84 14.85
15.91 4.97 5.92 8.93 11.97 14.87 14.97 15.89 10 11.88 15.94 18.01
19.98 5.97 5.98 14.95 17.01 32.01 9.88 11.91 13.01 36.01 2 14.94 23.78
24.01 5.95 10.89 10.9 11.9 17.99 18.77 37.01 1 4.06 7.89 10.88 10.95
16.03 20.75 20.8 23.71 2.92 3.89 18.99 19.01 19.89 23.7 23.75 27.01
27.64 27.65 35.57 40.02 3.05 4.09 9.9 10.86 11.94 16.04 19.84 23.74
27.98 39.98 9.04 13.95 17.89 19.74 19.76 20.77 20.82 20.84 20.89 20.92
20.94 20.96 21.74 23.85 26.67 26.84 28 31.61 31.7 31.98 35.99 2.9
12.33 12.95 12.96 15.77 16.8 17.9 17.92 19.78 19.81 19.92 19.94 22.01
26.75 26.88 27.73 36 3.09 3.87 4.13 5.04 8.86 10.92 11.82 12.84 12.87
12.94 17.78 17.82 17.96 18.8 19.95 21.73 23.82 23.88 23.89 24.7 26.86
27.82 28.01 31.99 35.01 35.54 2.88 3.67 4.12 8.05 9.06 9.33 9.92 11.03
11.34 12.88 13.93 14 16.08 17.95 22.73 24.68 25.67 26.65 26.78 26.94
26.99 27.79 27.85 31.75 31.8 36.98 43.02 1.98 2.86 3.12 3.65 3.83 4.15
4.16 7.05 7.87 11.33 12.86 15.05 15.67 16.06 18.85 18.88 19.96 21.81
21.9 22.99 23.9 26.73 26.8 26.96 27.7 27.71 27.75 27.77 29.01 34.98
35.67 35.97 2.85 3.13 4.18 5.05 8.67 9.08 9.93 9.96 13.82 13.84 13.85
13.87 14.77 15.15 18.9 18.96 20.86 21.8 21.93 23.96 23.97 26.01 26.98
27.91 30.01 31.93 34.01 35 35.61 2.67 2.78 2.82 3.75 3.77 3.81 4.19
4.21 4.32 4.91 7.84 7.85 8.09 8.33 11.67 12.04 13.98 14.18 15.07 15.48
15.54 15.7 15.72 15.73 16.82 16.83 16.85 16.86 16.92 16.94 16.95 17.34
17.67 17.77 17.81 17.85 18.87 18.92 18.93 21.83 21.92 22.8 22.86
23.68))
(setf snd (snd-zero 0 1))
(setf *table*
(dotimes (i (length harmonics) (maketable snd))
(setf snd (sim snd (scale-db (nth i amplitudes) (build-harmonic (nth i
harmonics) 4096))))))
(set-sound-srate *sound-srate*)
(setf freq-envelope (pwl 0 0.0 3 171.0 6 172.0 10 0.0 10))
; (remember to make the duration the same as the last number of the pwl, ie 10)
(setf noise (mult 0.3 freq-envelope (hp (noise 10) 150)))
(hzosc (sum noise freq-envelope))
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