15 Hz
Infrasound (below 20 Hz) · B-1
Turn the volume down before you play. A pure tone is harder on the ears than music at the same level.
Infrasound
Bass you feel rather than hear. Most speakers can barely produce anything below this.
| Wavelength | 22.87 m |
|---|---|
| Period | 66.67 ms |
| Nearest note | B-1 |
| Off by | -49 cents |
| Audible | No |
| Harmonics | 30 Hz · 45 Hz · 60 Hz |
| One octave down | 7.5 Hz |
| One octave up | 30 Hz |
How to read this
- Hertz counts how many times the air vibrates per second. The bigger the number, the higher the pitch.
- Wavelength is the speed of sound (343 m/s at 20 °C) divided by the frequency. That makes 20 Hz seventeen metres long and 20 kHz under two centimetres.
- People hear roughly 20 Hz to 20 kHz, but the upper limit drops with age. Past about 15 kHz, some hear the tone and some do not.
- Hearing nothing does not mean the equipment is broken. Small speakers cannot reach the low notes, and for the high ones it is the ear that gives up first.
Frequently asked questions
Q. What does 15 Hz sound like?
It is a pure tone vibrating 15 times a second. It sits outside the usual human range of 20 Hz to 20 kHz, so most people will hear nothing.
Q. What is the wavelength of 15 Hz?
22.87 m in air. Sound travels 343 metres per second through 20 °C air, so the wavelength is that distance divided by 15.
Q. What note is 15 Hz?
The nearest note is B-1, and it is 49 cents flat. A semitone is 100 cents, so that is about 49% of a semitone away.
Q. I cannot hear 15 Hz — is something wrong?
Small speakers can barely produce bass this low. Try headphones or a larger speaker before assuming anything is broken.
Q. What are the harmonics of 15 Hz?
The whole-number multiples: 30 Hz, 45 Hz, 60 Hz. An octave up is double, 30 Hz; an octave down is half, 7.5 Hz.
Nearby frequencies
Frequency doubles for every octave, so closeness is measured in ratios, not differences.