Spectrogram analysis help

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steve
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Re: Spectrogram analysis help

Post by steve » Fri Jan 12, 2018 12:30 am

Use a large "Size" setting.
You can also get numeric data by exporting.
See: http://manual.audacityteam.org/man/plot_spectrum.html
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

SandyPandy
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Re: Spectrogram analysis help

Post by SandyPandy » Thu Feb 01, 2018 11:38 pm

Hi!
So, I exported the data that gives me the exact values of the frequency peaks...but I had the following problems:

1. The maximum frequency as indicated by the exported data did not match what was shown on the sepctrogram graph. For the same audio I had put on the forum, the max frequency as indicated by the spectrogram seems to be slightly over 6350 Hz, but when I export the data (i have attached below), isn't the max frequency being shown as 6328.125000 (that is the lowest dB which is indicated by a peak?...correct me if I am wrong)

2. I am unable to locate the minimum frequency. All I am able to speculate from the graph is that it must be around 6270 to 6280 Hz. But from FFT analysis, I am not able to discern the min frequency.

3. What would be the uncertainty for the frequency values? Since it has 6 decimal places, I intially thought it would be +- 0.000001, but later I noticed that all the frequency values always had 0 in the last 3 decimal places, and as for the first three decimal places, they always were multiples of 125...like XXXX.125 or XXXX.750....or XXXX.375....so would the uncertainty be something else...perhaps +-0.125/2 (like least count divided by 2) = +-0.0625 Hz?

Frequency (Hz) Level (dB)
46.875000 -60.942871
93.750000 -60.645042
140.625000 -64.228699
187.500000 -67.088730
234.375000 -69.408409
281.250000 -70.791985
328.125000 -70.735794
375.000000 -71.338165
421.875000 -70.295227
468.750000 -69.950638
515.625000 -70.521271
562.500000 -69.931786
609.375000 -69.874748
656.250000 -72.334785
703.125000 -72.660378
750.000000 -73.218323
796.875000 -71.983650
843.750000 -71.714630
890.625000 -72.691208
937.500000 -74.205315
984.375000 -71.962967
1031.250000 -66.297813
1078.125000 -67.228752
1125.000000 -64.620605
1171.875000 -67.735695
1218.750000 -70.234802
1265.625000 -69.856133
1312.500000 -70.181618
1359.375000 -70.847481
1406.250000 -72.037132

steve
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Re: Spectrogram analysis help

Post by steve » Fri Feb 02, 2018 1:45 am

The "Size" setting that you are using with the sample rate of your audio is giving you an analysis of frequencies at intervals of 46.875 Hz.
Other than that, I can't work out what you are asking.
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

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