Ģ129 relations: A (musical note), A Brief History of Time, A Dark Traveling, A♭ (musical note), A♯ (musical note), ABC Local Radio, Ableton Operator, Absolute threshold, Absolute threshold of hearing, Absorption band, Absorption spectroscopy, Absorption wavemeter, Accessory pigment, Accurizing, Acoustic attenuation, Acoustic dispersion, Acoustic lobing, Acoustic metamaterial, Acoustic phonetics, Acoustic rheometer, Acoustic seabed classification, Acoustic tag, Acoustic theory, Acoustics, Acousto-optics, Acoustoelastic effect, Acronyms and abbreviations in avionics, Action potential, Action-angle coordinates, Active Denial System, Active shutter 3D system, Active vibration control, Adaptive behavior (ecology), Adaptive Transform Acoustic Coding, Additive synthesis, Additive white Gaussian noise, Advanced Mobile Phone System, Air-ground radiotelephone service, Airband, Aircraft emergency frequency, Aircraft noise, Airport/Facility Directory, Airtel India, Airy wave theory, Albert Abrams, Alexanderson alternator, Alexanderson Day, Algol variable, All I Need (Radiohead song), All-pass filter.
Frequency is the number of occurrences of a repeating event per unit of time.