# Tone & Frequency Generator A precise tone from 20 Hz to 20 kHz, synthesised live in your browser — tune an instrument to A440, test left and right speakers, find your treble limit. Nothing downloads, nothing uploads. Start at a low volume — especially with headphones. High frequencies can be loud before they feel loud. ## One oscillator, many jobs This tool plays a pure, precisely pitched tone from 20 Hz to 20 kHz — the span of human hearing — synthesised live by your browser's audio engine. The slider moves **logarithmically**, like hearing does, so the musically useful range doesn't crowd into the first centimetre. Type an exact frequency, or use the presets. ### Tuning an instrument The 440 Hz preset is **A4 concert pitch**, the standard reference for tuning. Play it, match your instrument's A, and tune the rest relative to it. The read-out shows the nearest note name for whatever frequency you dial in, so you can generate any reference pitch (e.g. 82.4 Hz for a guitar's low E). ### Testing speakers and headphones Use the **Left only / Right only** channel switch to confirm your speakers are wired the right way round and both drivers work — the classic stereo test. Sweep the low presets to find where your speakers give up: many small speakers produce little below 100 Hz, and a rattle or buzz on a pure low tone points to a loose driver or resonating furniture. The 1 kHz tone is the standard reference level engineers use to calibrate equipment. ### The hearing-range check (with a caveat) Human hearing tops out around 20 kHz in childhood and drifts down with age; many adults hear little above 15–16 kHz. Trying the high presets is a fun, *rough* self-check — but this is not a hearing test: your speakers, volume setting, and room matter as much as your ears. If you have real concerns about your hearing, see an audiologist for a calibrated audiogram. ### Privacy & safety The tone is generated on your device by the Web Audio API — nothing is downloaded, uploaded, or logged. Volume defaults low on purpose: pure tones concentrate all their energy at one frequency, so treat loud high-pitched tones with the same respect as any loud sound, especially in headphones. --- *Source: [ocxly.com/tone-generator.html](https://ocxly.com/tone-generator.html) — OCXLY, free 100% client-side privacy-first tools. Free online tone generator: any frequency from 20 Hz to 20 kHz with sine/square/triangle/sawtooth waves, A440 tuning pitch, left/right speaker test, and note-name readout. Runs entirely in your browser.*