Pitch is frequency measured in Hertz; A4 = 440 Hz is the universal tuning standard

Pitch is the ear perception of frequency — the number of complete wave cycles per second, measured in Hertz (Hz). Higher-pitched sounds have shorter wavelengths; lower-pitched sounds have longer wavelengths. The human hearing range spans roughly 20 Hz to 20 kHz. The universal master tuning standard sets note A (above Middle C) at 440 Hz, so that all instruments sound in tune with one another. In DAWs and MIDI environments, Middle C is C3 (or C4 in some conventions) and provides the pitch register midpoint between bass clef and treble clef.

Examples

A4 = 440 Hz. An octave above is A5 = 880 Hz; an octave below is A3 = 220 Hz. The dog whistle operates in the super-audible range (above 20 kHz).

Assessment

State the frequency of A4. Explain why the 440 Hz standard is necessary for ensemble performance. Convert: what is the frequency of A5?