IndexRoom & AcousticsNote Frequency
Note Frequency
Every piano key as a frequency and wavelength, with a tone generator.
Tap a key to select it. On a phone, swipe the keyboard sideways.
| Harmonic | Frequency | Nearest note | Offset |
|---|---|---|---|
| 1 | 440 Hz | A4 | +0 ¢ |
| 2 | 880 Hz | A5 | +0 ¢ |
| 3 | 1,320 Hz | E6 | +2 ¢ |
| 4 | 1,760 Hz | A6 | +0 ¢ |
| 5 | 2,200 Hz | C♯7 | −14 ¢ |
| 6 | 2,640 Hz | E7 | +2 ¢ |
| 7 | 3,080 Hz | G7 | −31 ¢ |
| 8 | 3,520 Hz | A7 | +0 ¢ |
Input
MIDI note number. 21 is the lowest piano key, 108 the highest.
440 Hz is standard. Baroque ensembles use 415, some orchestras 442 or 443.
How it works
Twelve equal steps
Western tuning divides the octave, a doubling of frequency, into twelve semitones of equal ratio. Each step multiplies the frequency by the twelfth root of two, about 1.0595. Counting semitones from the A above middle C:
With MIDI note numbers, where A4 is 69:
Cents
A cent is one hundredth of a semitone, used to describe small tuning differences:
Harmonics
A musical tone is a stack of whole-number multiples of its fundamental. The table shows where each lands. The third harmonic is 2 cents sharp of a tempered fifth, the fifth is 14 cents flat of a tempered third and the seventh is 31 cents flat. Equal temperament is a deliberate compromise that makes every key equally usable.
Why an audiophile cares
The piano's lowest A is 27.5 Hz and its highest C is 4186 Hz. Fundamentals of almost all music sit below 5 kHz; everything above is harmonics and air. Knowing which note a room boom or a resonance sits on makes it far easier to track down.