Online tone generator

How to use it

Pick a waveform, set the frequency with the slider or type an exact value, and press Play. Start with the volume low and turn it up slowly - your device's own volume control matters too. The slider is logarithmic, so every octave gets the same space and low frequencies are as easy to set as high ones. Your settings are remembered in this browser for next time.

Testing speakers and finding rattles

This is how we use it on the bench. Play a sine wave through the speaker at moderate volume and slowly sweep from about 40 Hz upwards. A healthy driver sounds like a clean, pure tone. Listen for:

• Buzzing or rattling at certain frequencies - often a loose cabinet panel, a port, a grille or a cable touching the cone, not the driver itself.
• Scraping at low frequencies - a rubbing voice coil, from a dropped speaker or an overheated coil.
• Nothing above a few kHz - a blown tweeter or a failed crossover. In a two-way speaker, try 5-10 kHz on its own.
• Distortion that comes and goes with volume - often the amplifier rather than the speaker.

For amplifier checks, a square wave makes clipping and ringing easier to see on a scope, and a steady sine is the usual signal for measuring output power and gain.

Look after your ears and tweeters

High frequencies at high volume can damage tweeters and your hearing faster than you'd expect, and square and sawtooth waves carry far more high-frequency energy than a sine at the same setting. Keep it quiet above about 5 kHz, and never feed a full-volume tone into a speaker you aren't sure of. Phone and laptop speakers can't reproduce the very lowest bass - use headphones or the speaker under test.

Questions

What frequency range can I generate?

Anywhere from 20 Hz to 20 kHz, the range of human hearing, in steps as fine as 0.1 Hz at the low end. Whether you can hear the extremes depends on your speakers and your ears - most adults can't hear much above 15-17 kHz.

Which waveform should I use to test a speaker?

A sine wave. It's a single pure frequency, so any buzz, rattle or distortion you hear is coming from the speaker or the cabinet, not the test signal.

Does it work on a phone?

Yes - it runs in the browser with the Web Audio API, on phones, tablets and computers. Turn off silent mode on iPhones if you hear nothing.