How this sweep works
Press Play the sweep and your browser generates a sine tone with the Web Audio API; no audio file is downloaded. Each pass slides from 220 Hz down to 110 Hz on a logarithmic curve in 1.4 seconds, then starts again at 220 Hz. Eight passes run back to back, about 11.2 seconds in all, and then the sweep stops on its own. The page plays at one fixed level and fades each start and stop, so your device's volume keys are the only loudness control.
Rel. excursion is (220 / f)², where f is the programmed frequency in hertz. It reads ×1.00 at 220 Hz and climbs to ×4.00 at 110 Hz as the sweep descends. The formula comes from a simple speaker model in which, at constant sound pressure, cone travel scales as about 1/f², so each octave down asks for four times the travel.
The ratio is arithmetic from the programmed frequency; the page does not listen to or measure your speaker. It plays at a fixed digital level, which does not hold sound pressure constant, so ×4.00 on the display does not mean your cone moves four times as far. The frequency changes and the automatic stop run on browser animation frames, which pause in a hidden tab, so the sweep stops as soon as the tab is hidden.
Frequently asked questions
Does this get water out of a phone speaker?
It can help with water sitting on or just behind the grille, which is the common case after a splash or a shower. At a low frequency the speaker cone travels far enough to push a droplet along with the air it moves, and a phone's own water-eject feature works on the same idea. The page cannot see whether any water moved, and a tone cannot dry the inside of a device. If liquid has reached the internals, power the device down and let a repair shop look at it.
Why a low tone instead of just a loud one?
Cone travel is what pushes a droplet along, and loudness is a separate thing. For the same sound pressure, a tone an octave lower asks the cone to move about four times as far, which is why the sweep falls from 220 Hz to 110 Hz. Turning the volume up past the point of distortion adds no useful travel.
How loud should I set the volume?
Loud enough to feel the speaker working, and no louder. Start low and set the volume before you press Play the sweep, since the page has no volume control of its own. Hold the device away from your ear and other people's, and play the sweep through its speaker with no headphones connected. Stop if the sound distorts, and lower the volume before you run it again: at a low frequency, distortion means the cone has hit its limit, which does no good and is hard on the speaker. If you hear nothing, check the selected audio output and the mute settings before you turn anything up.
It still sounds muffled after a few runs. What now?
Stop running the sweep and let the device sit somewhere dry and warm, but not hot. Keep it away from a hairdryer, which pushes moisture further in. Muffled sound that lasts after drying is often not water at all: a grille packed with lint or pocket dust sounds much the same, and a soft brush does more than any tone. If the speaker crackles or rattles at low volume, the cone may be damaged, and no sound can fix that, so have a repair shop assess it.
Is this the same as the water eject sound my phone plays?
The principle is the same, a low tone that moves the speaker cone, but the exact frequencies and pattern differ by device. A phone's built-in feature knows its own speaker and can drive it to match. This page knows nothing about your hardware, so it sweeps the same 220–110 Hz band at the same fixed level on every device, and your browser and system settings decide which speaker plays it.
