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Musical note

A4

  • A4
  • 440 Hz
  • MIDI 69

A4 is MIDI note 69, sounding at 440 Hz in equal temperament with A4 = 440 Hz. Its wavelength in air is 0.7795 m, and it sits in octave 4.

Pitch

Scientific pitch notationA4
MIDI note number69
Frequency440 Hzequal temperament, A4 = 440 Hz, a convention rather than a constant
Pitch classA (9)
Octave4

As a sound wave

Wavelength in air0.7795 mat 343 m/s, dry air at 20 °C
Period2.2727 ms
Frequency one octave up880 Hzdoubling the frequency
Frequency one octave down220 Hz
AudibleYeshuman hearing runs roughly 20 Hz to 20 kHz and narrows with age

Intervals from here

Octave belowA3 · 220 Hz
Perfect fifth belowD4 · 293.66 Hz
Semitone belowG#4 · 415.3 Hz
Semitone aboveA#4 · 466.16 Hz
Major third aboveC#5 · 554.37 Hz
Perfect fifth aboveE5 · 659.26 Hz
Octave aboveA5 · 880 Hz

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Nearby notes

The same note in other octaves

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Every value on this page was computed from “note a4” by Nerdulator’s reference engine. Nothing here was retrieved from a database of answers or written by a model.