Speaker Distortion Analyzer — Rattle & Buzz Test

Most audible speaker faults are mechanical: a loose grille or cabinet panel, a port that chuffs, an object on a nearby shelf that resonates, or — inside the driver — a rubbing voice coil, a torn surround, or a cone being pushed past its excursion limit. These buzzes and rattles only appear at the particular frequency that excites them, so the reliable way to find them is to sweep a clean sine tone across the whole range and listen. This tool plays that tone with the Web Audio API (an oscillator routed through a gain control to your speakers or headphones), so the signal itself is mathematically pure — any rattle, buzz or harsh edge you hear is coming from the speaker, the cabinet, the room, or something loose nearby, not from the test signal. You can also generate a precise reference pitch for comparison using the online tone generator.

There are three ways to drive it. The log sweep glides slowly from 20 Hz to 20 kHz over a duration you choose; when you hear a noise you press Mark and the current frequency is logged so you can return to it. The sustained tone lets you park on one frequency (or on a marked one) and listen closely, nudging the slider a little either side to confirm exactly where the rattle peaks — a technique familiar to anyone doing loudspeaker enclosure diagnosis or Bl-linearity checks by ear. The stress ramp holds one frequency while slowly increasing the level, which makes a marginal rattle or the onset of driver distortion easier to provoke — but because rising level is exactly what damages drivers and ears, it starts very low, is capped a few dB below full scale (about -5 dBFS) — still potentially very loud — and should be stopped the moment anything sounds wrong. If you also want to check the speaker's tonal coverage alongside distortion hunting, the companion speaker frequency response test plays the same logarithmic sweep with a band-by-band listening guide.

The optional microphone mode captures the sound in the room and draws its spectrum, marking the fundamental (f) and its harmonics (2f, 3f…). When energy piles up at those harmonics relative to the fundamental, it suggests distortion, and the tool shows a rough percentage as a guide. Be honest with yourself about what this can mean: a laptop or phone speaker is already a distorting source, the built-in microphone adds its own non-linearity and frequency colouration, and browsers often apply automatic gain control or limiting that you cannot fully disable. So the harmonic indicator is a relative, uncalibrated hint — great for spotting a speaker that grossly distorts, useless as a real Total Harmonic Distortion (THD) figure. For a number you can trust, use a calibrated measurement microphone with software such as REW, or a dedicated audio analyzer, on a known-clean playback chain.