Tone Generator

Plays a precise, adjustable audio frequency from 20 Hz to 20 kHz — the full range of human hearing — with a choice of waveform, volume control and independent left/right channel output.

Checking speaker or headphone channels

Playing the tone through the left channel only, then the right only, confirms which physical speaker or earbud is wired to which side — a fast way to diagnose a 'my left earbud sounds wrong' complaint or to verify a new speaker installation is wired correctly, without needing test audio content.

Tuning and reference frequencies

A4 = 440 Hz is the standard concert pitch reference most instruments are tuned against. Playing a steady sine wave at an exact frequency gives a clean reference tone for tuning by ear, or for testing whether an instrument or a recording device is reading pitch accurately.

Hearing range checks

Sweeping upward from a lower frequency toward the top of the range gives a rough, informal sense of hearing range — most adults stop perceiving tones somewhere between 15 and 17 kHz, with the upper limit dropping further with age, a natural process called presbycusis. This isn't a substitute for a proper audiology test, but it's a reasonable way to notice a change worth getting checked.

Waveform choice

Sine is a pure single frequency with no harmonics, the standard choice for tuning and hearing checks. Square and sawtooth waves contain additional harmonic frequencies layered on top of the fundamental, which makes them sound noticeably harsher and louder-feeling at the same volume setting — useful for stress-testing a speaker's response, less pleasant for extended listening.