20 Hz is the figure usually given for the lower limit of human hearing (20 Hz to 20 kHz). Below it, sound is felt more than heard. Few speakers reproduce it at any useful level, so on a phone or laptop this tone may be silent.
Which note 20 Hz is at other reference pitches
“In tune” depends on what A4 is tuned to, so the same frequency is a slightly different distance from the nearest note in each tuning.
| Reference | Nearest note | That note | 20 Hz is |
|---|---|---|---|
| A4 = 440 Hz · Standard (ISO 16) | E♭0 | 19.45 Hz | +48.7¢ |
| A4 = 432 Hz · “Verdi” pitch | E0 | 20.23 Hz | −19.6¢ |
| A4 = 442 Hz · Orchestral | E♭0 | 19.53 Hz | +40.8¢ |
| A4 = 415 Hz · Baroque pitch | E0 | 19.43 Hz | +50.0¢ |
Octaves of 20 Hz
Doubling a frequency raises it an octave and halving lowers it one, so these all have the same note name and the same offset from it.
Harmonics of 20 Hz
A real instrument playing 20 Hz also sounds whole-number multiples of it. The first eight, and the notes they fall nearest:
| Harmonic | Frequency | Nearest note | Off by |
|---|---|---|---|
| 1 | 20.00 Hz | E♭0 | +48.7¢ |
| 2 | 40.00 Hz | E♭1 | +48.7¢ |
| 3 | 60.00 Hz | B1 | −49.4¢ |
| 4 | 80.00 Hz | E♭2 | +48.7¢ |
| 5 | 100.00 Hz | G2 | +35.0¢ |
| 6 | 120.00 Hz | B2 | −49.4¢ |
| 7 | 140.00 Hz | C♯3 | +17.5¢ |
| 8 | 160.00 Hz | E♭3 | +48.7¢ |
Period and wavelength
One cycle of 20 Hz lasts 50.000 milliseconds; in air at 20 °C, where sound travels at about 343 metres a second, one wavelength is 17.15 metres.