How the test works
Choose a channel in the first row and a signal in the second, then press Play. The tone is a 440 Hz sine wave, the same pitch as the A that orchestras tune to, played in the left ear, the right ear or both. The sweep glides from 20 Hz to 20 kHz over twenty seconds and repeats, with the current frequency shown in the corner of the panel. The phase check plays the tone in both ears and inverts the right ear every two seconds; the chip on the panel says which state you are hearing. You can switch checks while the sound plays and each one you hear is added to the list. Press Stop to finish.
Everything is generated in the browser with the Web Audio API and sent to the output your system has selected. With Bluetooth headphones, the system may take a moment to switch to the higher-quality profile when playback starts, so the first second can sound dull; that is the connection, not the headphones. Nothing is recorded and the microphone is not used.
What the result means
The result card counts the checks you played out of five: left, right, both, phase and sweep, and adds the output latency the browser estimates when it reports one. The card records what was played; you are the judge of what you heard.
- Left in the left ear, right in the right. The wiring and the marking agree.
- A silent ear. A broken wire near the plug or the earpiece, a dirty mesh, a balance setting, or a Bluetooth earbud that has not connected. See below.
- The phase check sounds different in its two states. The drivers are in phase. A pair that sounds the same in both states has one driver reversed.
- The sweep is heard smoothly from the bottom to wherever your hearing ends. The drivers cover the range. A drop-out in the middle is unusual and points to a damaged driver.
- Crackle during the sweep at some frequencies. A driver that rubs or a torn diaphragm. Turn the volume down and repeat; if the crackle stays at the same frequency, it is the driver.
What to do if something is wrong
For wired headphones, wiggle the cable gently at the plug and at the earpiece while a tone plays: sound that comes and goes as you move the cable is a broken conductor, and a replacement cable fixes it on models with a detachable one. Try a different device with the same headphones to rule out the socket. Clean the mesh of each earpiece with a dry soft brush, never with a liquid.
For Bluetooth headphones and earbuds, forget the pairing on the computer and pair again, charge both earbuds fully, and make sure the operating system is using the stereo profile rather than the headset (hands-free) profile, which is mono and low quality. In the sound settings, centre the balance and disable any spatial audio or equaliser, then run the left, right and phase checks again.
When to return or claim the warranty
A new pair with a silent side, a reversed driver revealed by the phase check, or crackle at normal volume is defective and should be exchanged within the return window. For a warranty claim, write down which check fails and, for a crackle, the frequency the sweep shows when it appears. Cables that fail from bending are the most common headphone warranty case and are usually covered in the first year; earpieces damaged by moisture, sweat inside non-waterproof earbuds, or a pulled cable are typically not.
Frequently asked questions
What should the phase check sound like?
The same tone plays in both ears and every two seconds the right ear is flipped upside down. In phase, the tone sits in a small spot in the middle of your head. Inverted, it spreads out, sounds hollow and seems to come from everywhere at once. If you hear that difference clearly, the two drivers are wired the same way. If both states sound identical and diffuse, one driver is wired in reverse and the headphones will have weak, unstable bass.
Bluetooth headphones play the tone late after I press Play. Is something wrong?
No. Bluetooth adds a delay between the computer and the earpiece, typically 100 to 250 milliseconds with the standard SBC codec and 40 to 80 with aptX Low Latency or similar codecs, and the browser cannot shorten it. The result card shows the output latency the browser estimates, when it reports one. The delay matters for games and video, not for this test: the tone, the sides and the sweep are the same whenever they arrive.
One earbud is quieter than the other. Is that a fault?
It can be, but check the easy causes first: earwax or debris in the mesh of the quieter earbud, a foam or silicone tip that no longer seals, and the balance slider in the operating system. Play the left and right checks in turn at the same volume. A difference that survives cleaning, new tips and a centred balance is a failing driver or a damaged cable near the plug.
Why do I stop hearing the sweep at 16 kHz when the box says 20 kHz?
Both limits can be true. The 20 kHz figure describes the driver; how high you hear depends on your age and your listening history, and most adults stop somewhere between 14 and 17 kHz. Also, Bluetooth codecs compress the signal and some cut everything above 16 to 18 kHz. Try the same headphones with a cable before you blame them.
Is there a way to check whether left and right are labelled correctly?
Yes: select Left and press Play. The sound must come from the earpiece marked L. Earbuds that are put in the wrong ears simply swap sides, and some over-ear models let you turn the headband either way, so the marking is the reference. Reversed sides in a wired pair with the marks respected mean the plug or an adapter is miswired.