Tone generator

Find a rattle. Sweep slowly from 40 to 200 Hz at a moderate volume. A loose speaker grille, a desk ornament, or a wall fixture will buzz only at its own resonant frequency, and the tone holds that frequency steady for as long as you need to hunt it down.

Check how high you can hear. Step through the presets: 10 kHz, then 15 kHz. Most adults top out somewhere between 12 and 17 kHz, and that is normal. One honest caveat: a silent 15 kHz tone on laptop speakers proves nothing, because small speakers often give out before your ears do. Use headphones for this one, at a low volume.

Verify both sides play. The tone goes to your default output equally on both channels, so with headphones on it should sound dead center. If one side is quiet or silent, the fault is downstream: the cable, a balance setting, or the device itself. Note that a full stereo check needs both channels working end to end; this tone confirms output exists but cannot isolate left from right by itself.

Identify a hum. Ground loop and mains hum sits at 50 or 60 Hz with a strong harmonic at 100 or 120 Hz. Play those frequencies and compare by ear against the hum coming from your speakers or subwoofer crossover. If they match, you are chasing electrical noise, not a blown driver.

If you want the intuition for where sounds live on the frequency axis, and why the slider on this page is logarithmic, read what an EQ is. An EQ is the same 20 Hz to 20 kHz axis with gain attached.

Hertz (Hz) is cycles per second: how many times the wave repeats each second. Doubling the frequency raises the pitch by one octave, which is why the slider is logarithmic. Equal slider travel is an equal pitch step, so 100 to 200 Hz takes the same distance as 5 to 10 kHz.

Waveforms differ in harmonics. A sine wave is one pure frequency and nothing else, which makes it the honest choice for hearing tests and rattle hunting. Square, triangle, and sawtooth stack harmonics on top of the fundamental, so they sound buzzy and noticeably louder at the same volume setting. That is also why they are easier to hear through background noise.

dBFS next to the volume slider is the tone's digital level, where 0 dBFS is the loudest a digital signal can be. This tool caps its output at -6 dBFS (half of full scale) and defaults well below that, because a browser tab has no idea how loud your amp and headphones are.

One caveat on accuracy. The generated frequency is digitally exact, but what you hear passes through the browser's output path, your OS mixer, DAC, amp, and speaker. A tone you cannot hear may have been lost anywhere along that chain, so try a second output device before blaming your ears. To check the other direction of that chain, your mic, run the free mic test next: it measures peak, noise floor, and tonal shape the same honest way.