60 Hz: mains hum in North America

Mains electricity in North America and parts of South America and Asia alternates at 60 Hz. Poorly shielded audio cables, ground loops and single-coil guitar pickups pick it up as a low hum, usually with its harmonics at 120, 180 and 240 Hz.

Because 60 Hz falls between two notes, mains hum is slightly out of tune with every key — one reason it is so easy to hear under music.

Which note 60 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.

Octaves of 60 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.

• 30.00 Hz · B0
• 120.00 Hz · B2
• 240.00 Hz · B3
• 480.00 Hz · B4

Harmonics of 60 Hz

A real instrument playing 60 Hz also sounds whole-number multiples of it. The first eight, and the notes they fall nearest:

Period and wavelength

One cycle of 60 Hz lasts 16.667 milliseconds; in air at 20 °C, where sound travels at about 343 metres a second, one wavelength is 5.72 metres.

Convert another frequency

Or hold 60 Hz as a steady tone, sweep from it, or beat it against a second tone in the tone generator. The note frequency chart lists every note from C0 to B8.

Frequently asked questions

Related frequencies

• 120 Hz — transformer hum at 60 Hz mains
• 50 Hz — mains hum in Europe and most of the world
• 100 Hz — transformer hum at 50 Hz mains