220Hz

220Hz is a frequency equal to 220 cycles per second, meaning a wave completes 220 oscillations every second. In physics the period of such a wave is approximately 4.55 milliseconds. When expressed as a sound, it produces a relatively low-mid pitched tone.

In music, 220Hz corresponds to the note A3, one octave below the standard concert pitch A4 at 440Hz. Because of this relationship the 220Hz tone is used in tuning instruments, especially those requiring reference to the lower octave such as euphoniums, tubas, and piano keyboards. Recorders and certain wind instruments likewise use it as a tuning reference for their lowest register.

Human hearing ranges roughly from 20Hz to 20kHz, with greatest sensitivity around the 3kHz to 5kHz band. Still, 220Hz falls comfortably within a perceptible range and is important for bass and sub-bass content in audio production. It is often included in the equalisation of audio tracks to provide warmth and fullness without causing distortion.

The 220Hz frequency also appears in various technical applications. Audio test equipment commonly outputs a 220Hz sine wave for calibration and verification because its frequency lies well within the audible range yet is above the predominant background noise. Some communication systems, especially older narrow‑band radio protocols, used 220Hz as a carrier or pilot tone. Additionally, 220Hz is one of the intermediate frequencies used in certain radio signal processing chains.

Because 220Hz is a simple integer multiple of low-power electrical line frequencies (e.g. 60Hz or 50Hz), it is occasionally used in metrology for measuring frequency response of electronic devices. The tone is also included in standardized test signals for digital audio equipment, providing a reference point for phase and amplitude accuracy.

Overall, 220Hz plays a modest but clear role in acoustics, music tuning, audio engineering, and certain radio communications, serving as a reliable reference point within both human hearing and technical measurement contexts.