Question: Do all farts really have similar sound frequency composition?
Short answer: Yes.
Long answer: Today’s question was actually submitted by one of our readers, who asks, “How variable is the distribution of frequencies? I was wondering if the Giuliani fart is indeed real… If you sampled from more people, you might have the low, middle, and high pitch farters…”
There are actually two parts to this question. The first concerns the variation in fart frequencies across individuals, which is real and sufficiently reliable to allow for people to be identified solely on the basis of the sound of their farts.
The second concerns the extent of this variability. To the casual listener, there seems to be an infinite variety of fart sounds. And yet, as we have discussed previously, in our database of over 2000 farts, the sound amplitudes are concentrated within a narrow band between 200 and 300 Hz, with a sharp concentration around 275 Hz. How is this possible?
To understand this phenomenon better, we compared two farts that sound very different to the human ear.
Here is an example of a deep-pitched fart:
And here is an example of a squeaky fart:
The two farts clearly sound quite different, and they were contributed by different people. Yet analysis of the frequency content reveals that the dominant frequencies are indeed similar:
The highest power across frequencies is shown by the orange-red colors. Clearly, in both cases, power is concentrated in a narrow range between 200 and 300 Hz, as reported previously.
Of course, there must be something in the frequency spectrum that accounts for the perceived difference, and we can only assume that it is the low-amplitude, high-frequency content of the squeaky fart. This can be seen as the faint trail of bluish color in the plot on the right, covering frequencies from about 500 to 800 Hz. The fact that these relatively weak signals dominate our perception could relate to the transfer function of the human auditory system. Or it could be related to melody perception in music: When listening to a chord sequence, people usually hear the melody as the top notes in each chord.
Another difference is that the squeaky fart, being comprised of both low and high frequencies, has its own harmonic structure (a compound interval). This might account for its more pleasing sound, which could theoretically be exploited in musical compositions. As far as we know, the Backstreet Boys are the only artists thus far to have recognized this possibility.
In any case, our Department of Flatoacoustics is actively researching this issue. But in the meantime, the conclusion that farts share a common frequency structure seems secure.