On 60 Hz mains, transformers and lighting ballasts buzz at 120 Hz — twice the mains frequency — and it is the second harmonic of 60 Hz ground-loop hum in audio.
Which note 120 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 | 120 Hz is |
|---|---|---|---|
| A4 = 440 Hz · Standard (ISO 16) | B2 | 123.47 Hz | −49.4¢ |
| A4 = 432 Hz · “Verdi” pitch | B2 | 121.23 Hz | −17.6¢ |
| A4 = 442 Hz · Orchestral | B♭2 | 117.07 Hz | +42.8¢ |
| A4 = 415 Hz · Baroque pitch | C3 | 123.38 Hz | −48.1¢ |
Octaves of 120 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 120 Hz
A real instrument playing 120 Hz also sounds whole-number multiples of it. The first eight, and the notes they fall nearest:
| Harmonic | Frequency | Nearest note | Off by |
|---|---|---|---|
| 1 | 120.00 Hz | B2 | −49.4¢ |
| 2 | 240.00 Hz | B3 | −49.4¢ |
| 3 | 360.00 Hz | F♯4 | −47.4¢ |
| 4 | 480.00 Hz | B4 | −49.4¢ |
| 5 | 600.00 Hz | D5 | +37.0¢ |
| 6 | 720.00 Hz | F♯5 | −47.4¢ |
| 7 | 840.00 Hz | A♭5 | +19.5¢ |
| 8 | 960.00 Hz | B5 | −49.4¢ |
Period and wavelength
One cycle of 120 Hz lasts 8.333 milliseconds; in air at 20 °C, where sound travels at about 343 metres a second, one wavelength is 2.86 metres.