Find out whether both speakers, or both sides of your headphones, are working and the right way round. Play each channel on its own, hear the difference between in phase and reversed polarity, sweep from deep bass to the top of the treble, and use pink noise to check balance and rattles.
One test plays at a time. Starting another stops the last.
Nothing is playing.
Esc also stops every sound, from anywhere on the page.
Turn your volume down first, especially on headphones.
Set your system volume low before the first play, then raise it while a test runs. Every signal here is capped at -12 dBFS peak, and the slider starts at 30 percent.
Peak -33 dBFS · -12 dBFS at 100%
Sound plays through your system's default output. To change it on macOS, open System Settings, Sound, Output. On Windows, open Settings, System, Sound, and choose where to play sound.
Every sound is generated inside this tab. Nothing is recorded or uploaded, and the page never asks for your microphone.
Press a side and listen for where the sound comes from. Left should come only from the left, right only from the right, and both from a point in the middle.
Three short bursts of pink noise. Broadband, so it is easy to place and shows a rattle or a dead tweeter.
Press a speaker to play that channel alone, or the middle button for both together.
Left, right, left, right, about 11 seconds. Useful from across the room, or to hear a side that is quieter than the other.
The same low noise, 80 to 500 Hz, plays on both sides. Sit centred between the speakers and compare the two states.
If in phase is the one that sounds vague and thin, one speaker has its plus and minus wires swapped. Swap the two wires on one speaker only, then test again. Headphones are wired at the factory and almost never fail this.
Steady pink noise until you stop it. On both channels it should sit dead centre; on one side, listen for buzzing panels, loose grilles, or a dull, missing top end.
While it plays, another side moves the noise without a gap; the lit button stops it. If the noise sits off centre from your listening position, check the balance slider in your sound settings before blaming a speaker.
Pink noise carries equal energy in every octave, so it sounds even rather than hissy, and every part of a speaker is working at once.
A sine tone glides on a logarithmic scale, so every octave takes the same time. Listen for where it appears, where it buzzes, and where it fades out. This checks your speakers, not your hearing.
20 Hz to 20 kHz, every octave a listener can hear.
Your reaction time moves a mark a little past the true point, so the 30 s sweep gives the closest answer. Laptop and phone speakers rarely play anything below about 100 to 150 Hz; silence there is normal, not a fault. Keep the level low: a steady sine puts all its energy into one driver.
Offered only when the output reports six or more channels. Most laptops, headphones, TVs, and soundbars expose stereo only, and the browser mixes everything down to two.
The channel count is read from the audio output, which the browser opens only after a click. Press Check this output, or play any test above.
The page cannot hear your speakers, so you are the judge. Mark each check as you go. Nothing is stored; copy the summary to keep it.
The left test played from the left side only, and sounded clean.
The right test played from the right side only, and sounded clean.
In phase sounded centred and full; right inverted sounded vague and thin.
Pink noise on both channels sat in the middle, with no rattle or buzz.
Filled in by the mark buttons under the sweep: lowest not marked, highest not marked.
Checks marked OK so far.
Every verdict is yours. The browser has no way to know whether sound came out, which side it came from, or whether it buzzed, and this page never opens the microphone to find out.
Your system's volume mixer and balance slider, the mono audio accessibility setting, spatial audio or virtual surround, equaliser apps, and Bluetooth codecs all sit between the browser and the speakers. Check them before the hardware.
Laptop and phone speakers rarely reproduce anything below about 100 to 150 Hz, and many headphones fade under 30 Hz. Silence at the bottom of the sweep on them is normal.
A steady sine tone puts all of its energy into one small driver at a time. Loud, the top octaves can damage a tweeter and your hearing, and they are easy to underestimate because they are hard to hear.
-12 dBFS peak cap · volume starts at 30% · 3 × 0.6 s pink noise bursts · log sweep 20 Hz to 20 kHz · polarity band 80 to 500 Hz · nothing recorded or uploaded
The other half of a device check: confirm your microphone with a live level meter and a clip to play back.
Play the sweep or pink noise here and watch a microphone in another tab show what your speakers really put out.
Turn the frequencies you marked on the sweep into note names, piano keys, and wavelengths.
Every signal is made inside this tab: pink noise from a seeded generator, a sine oscillator for the sweep, and a triangle wave for the chime. Each test runs through a channel merger whose inputs are wired to exactly the output channels the test names, so left means the first output channel and nothing else, and the polarity test inverts only the right channel with a gain of minus one. The sweep's frequency is scheduled on the audio clock with an exponential ramp, and the readout evaluates the same curve at the moment the sound leaves your speakers, using the output delay the browser reports. Signals peak at -12 dBFS at full volume and fade in and out, so nothing clicks.
Start with your system volume low; the page starts at 30 percent and caps every signal at -12 dBFS. Press Left and only the left speaker or ear cup should sound. Then Right, then Both, which should seem to come from a point in the middle.
Sit centred between the speakers and play the polarity test. In phase should sound solid and centred, right inverted vague and thin. If it is the other way round, one speaker has its two wires reversed.
Run the sweep quietly and mark where the tone appears and where it fades out. Use pink noise to check balance and hunt down rattles, then mark each check OK or Problem and copy the summary.
Each test is wired through a channel merger to exactly the output channels it names, so the other side carries digital silence. When the output reports six channels, the same routing drives a 5.1 check with a low-passed subwoofer feed.
Three bursts of pink noise cover the whole range and expose a dead tweeter or a buzzing panel; a two-note chime is gentler on headphones. Alternate mode plays left, right, left, right while you walk the room.
Noise limited to 80 to 500 Hz plays on both sides and switches every four seconds between in phase and right inverted. Hold either state to compare at your own pace.
A logarithmic sine sweep from 20 Hz to 20 kHz, or 20 to 200 Hz for a subwoofer, over 10, 20, or 30 seconds in either direction. The frequency shown comes from the audio clock, corrected for output delay.
Pink noise on the left, the right, or both, moved between sides without a gap, for checking balance from your seat and tracking down rattles at a level you choose.
Every signal peaks at -12 dBFS at full volume, the slider starts at 30 percent, every start and stop is faded so nothing clicks, and Esc silences the page at once.
Work from the speakers back to the computer. The speaker marked L should sit on your left as you face the screen, and the cable from the left output should reach it; on an amplifier or receiver, swap the two speaker cables at one end. On headphones and earbuds, check the L and R markings, since some are easy to wear the wrong way round. Then check software: some sound drivers, equaliser apps, and audio interfaces remap channels. If the Left button here plays on the left, the browser and everything after it are wired correctly.
First look for the balance control. On Windows it is under Settings, System, Sound, in the output device's properties; on a Mac under System Settings, Sound, Output. A balance pushed all the way to one side silences the other. Next check the cable: a 3.5 mm plug that is not fully pushed in often loses one channel, and so does a worn cable that crackles when you move it. Swapping the two speakers, or the two cables, shows whether the fault follows the speaker or stays with the output.
A speaker's cone should move outwards when the signal goes positive. If one speaker has its plus and minus wires swapped, its cone moves in while the other moves out, and the two partly cancel. Low notes cancel most, so the sound loses bass and no longer forms a clear image in the middle; it seems to come from the sides or from inside your head. The test plays the same low noise on both sides, in phase and then with the right channel inverted. If the inverted state is the one that sounds centred and full, swap the red and black wires on one speaker only.
Small drivers in a small box cannot move enough air for low notes. Laptop and phone speakers rarely reproduce anything useful below about 100 to 150 Hz, and many small Bluetooth speakers stop around 80 to 100 Hz; what you hear as bass in music from them is mostly the overtones above the note. Good headphones usually reach 20 to 30 Hz, and a subwoofer is built for exactly the bottom of the range. Silence at the low end of the sweep on a laptop is normal, not a fault.
Yes. Bluetooth adds a delay of roughly 100 to 300 ms, which the sweep readout corrects for when the browser reports it, and many codecs trim the very top of the range. If the headset's microphone is in use, it may switch to a narrow hands-free mode that sounds muffled and is sometimes mono. Spatial audio, head tracking, Windows Sonic, and Dolby Atmos for headphones deliberately blend the channels, so left can leak into right and the polarity test sounds odd. Switch them off for a clean check.
Almost always a mono setting. Mono audio is an accessibility option that mixes left and right together, so a listener with hearing in one ear misses nothing. On a Mac it is under System Settings, Accessibility, Audio; on Windows under Settings, Accessibility, Audio; on an iPhone under Settings, Accessibility, Audio and Visual; on Android in the accessibility settings. A single Bluetooth speaker, a smart speaker, or a TV soundbar may also be mono by design. If you rely on mono audio, leave it on; the test is only telling you it is there.
Quietly: no louder than normal conversation at your listening position. A sine tone puts all of its energy into one frequency, which a tweeter can only take in small amounts, and the highest octaves can be harmful before they sound loud, especially in headphones. This page caps every signal at -12 dBFS and starts the slider at 30 percent, but your system volume and amplifier decide the real level. Set them low before the first play, raise them only as far as you need, and stop at once if anything buzzes, distorts, or hurts.
Only when the browser is given more than two channels. If the output reports six or more, the surround card offers front left, centre, front right, surround left, surround right, and a subwoofer channel low-passed at 120 Hz, one at a time or in turn. Most laptops, headphones, TVs, and soundbars expose stereo only, and an HDMI receiver usually shows six channels only after the computer's output is set to 5.1 in its sound settings. If a speaker answers to the wrong name, the device or its speaker setup maps channels in a different order.
No. What you hear at each end of the sweep depends on the speakers or headphones, the room, the volume, and your ears all at once, and none of them is calibrated. Use the marks to compare two pairs of speakers, or the same pair before and after a change. To check your hearing, see an audiologist, who uses calibrated headphones and tones at measured levels.
No. Every sound is generated inside this tab with the Web Audio API, nothing is uploaded, and the page never asks for your microphone. That is also why it cannot hear your speakers, so every judgement is yours. Your OK and Problem marks live only on this page and are gone when you leave or reload; copy the summary if you want to keep it.
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