Regarding ultra-low pitch

Frequently Asked Questions about Ultra-Low Pitch

Q1. I listened to a recording labeled A-2 (lowlowlowlowA), but isn’t it just making popping sounds at intervals of about 6.875 Hz?
Also, since the lower limit of human hearing is E0 (lowlowlowE), wouldn’t anything audible already be within the audible range?

A1. If it is consistently producing popping sounds at 6.875 Hz, then it is correctly A-2 (lowlowlowlowA). The human voice can be perceived as popping sounds even outside the audible frequency range.
First, sound is essentially “vibrations (especially of air) perceived by the auditory system.”
Humans perceive the frequency of these air vibrations as pitch.
For example, if the air vibrates 440 times per second, we perceive it as A4 at 440 Hz.

The human voice is mainly produced by vibrations of the vocal folds. These vibrations disturb the air and are heard as sound.
If they vibrate 220 times per second, it is A3; if 6.875 times per second, it is A-2.
This video (https://youtube.com/shorts/R4FIwbr46qs) can also be helpful, as it demonstrates how beats become pitch.

Regardless of vocal technique, as pitch decreases (or playback speed is reduced), the popping or crackling sounds of the vocal folds (so-called “pop noise”) become audible.
This is generally common to all vocal techniques. What differs is the mode of vibration. For example, in chest voice, the vocal folds are relaxed and vibrate as a whole with collisions, while in falsetto, they are stretched and only partially vibrate.

In simple terms, the vibration period of the vocal folds is the actual pitch, and the actual pitch is the vibration period of the vocal folds. There is no difference between high and low pitches in this regard.

However, pitch requires continuous vibration. Sounds with extremely unstable periods or those with only a single isolated cycle cannot be recognized as having pitch.

Q2. But if you pitch-shift that A-2 up by four octaves, wouldn’t it just shift the frequency components of the pop noise by 16 times rather than becoming A2?

A2. That is a limitation of the equipment.
The reason is that “the device does not recognize A-2, so it cannot properly apply pitch shifting.” This is similar to how it is impossible with ordinary equipment to record an inaudible high frequency like G11 (hihihihihihihiG) and then lower it by octaves.
If a device capable of recognizing A-2 were used for pitch shifting, it would correctly become A2. Likewise, if a signal already sped up 16 times from A-2 were processed by the device, it would be recognized as A2.

(By the way, doubling playback speed always doubles the frequency and raises the pitch by one octave. Quadrupling raises it by two octaves. This is independent of pitch recognition by machines, so it can be used for measuring low frequencies.
Speed changes that do not alter pitch involve waveform editing to artificially restore the original pitch.)

Q3. Then if someone just says “ah” once every 100 seconds, that’s vibrating the air once every 100 seconds, so is that 0.01 Hz, i.e., E-11?

A3. Physically, yes, but here it is not considered continuous phonation.
Indeed, if someone could say “ah” 440 times per second, it would likely be heard as A4.
However, this type of sound—where “ah” is repeatedly rearticulated—includes intervals where no phonation occurs.
Even if there happens to be silence between pop sounds, it is treated differently from phonation that continues uninterrupted, and thus is not considered a single sustained sound.
Even in vocal fry, if there are breaths or complete pauses in phonation, it is considered invalid.