How to use it
Put your headphones on, or sit centred in front of your speakers, and turn the device volume down. Press Turn sound on, play the reference tone and raise the volume until it is clearly audible but comfortable. Then work through the six tabs from left to right. Each tab says in one line what you should hear. In the checklist mark every test OK or Problem, and press Copy results to get a plain-text summary. Stop or Esc silences everything.
Controls
- Volume: a relative slider with a fixed ceiling. At the maximum, peaks are at most half of full scale (−6 dBFS), the sweeps are quieter, and one jump upward is limited to 20 dB. Every change is ramped. The volume always starts low and is not remembered.
- Tabs: click, tap or use the arrow keys. Changing tab stops the sound.
- Left, Right, Both, Auto cycle: the chime plays until you stop it. The short checks use the keys shown on the buttons (left, right and down arrows) and P to replay.
- Sweeps: Play, Pause (the tone is held at that frequency), Resume and Stop. The slider is logarithmic, so equal distances are equal musical intervals. Moving it holds a steady tone. On the range tab, Mark buttons store the lowest and highest frequency you hear.
- Checklist and Copy results: your marks, balance and answers are kept in this browser only.
How it works
Left-only sounds are built as two-channel audio in which the unused channel contains exact digital zeros. If you still hear something on the “silent” side, it comes from your equipment, from sound leaking around the ear or reaching both ears from a speaker, not from this page. Signals pass through a master gain and nothing else: no compressor, limiter or equaliser.
Polarity. Inverting polarity multiplies a signal by −1, a 180° shift at every frequency at once. The test uses low-frequency noise, identical on both sides or inverted on one. When two loudspeakers play inverted bass, their waves cancel where the wavelength is long compared with the path difference; at 100 Hz the wavelength is about 3.4 m (343 m/s divided by 100 Hz). Bass thins out and the sound becomes hard to place. Headphones have no such acoustic cancellation, but an inverted pair still tends to sound diffuse and “inside the head”.
Balance. The two channels carry the same noise. A level difference is measured in decibels:
A difference of 6 dB is roughly a factor of two in amplitude and 1 dB is about 12 percent. Many listeners notice about 1 dB as a sideways shift, though this varies. An offset can come from the headphone drivers, the fit, the two ears, or a balance setting on the device.
Sweeps. The frequency rises exponentially with time t, so every octave takes the same time (about 4 s for the 20 Hz to 20 kHz sweep, which lasts 40 s):
Amplitude stays constant, but your ear does not: it is most sensitive between roughly 2 and 5 kHz, so the middle of the sweep sounds much louder than the ends. The range you hear is limited by the equipment (small drivers give little below 50 Hz) and by you; the upper limit of hearing falls with age, and many adults hear nothing above 15 kHz or lower. Driver matching plays the same sweep in both channels. Level differences between the ears help the brain place a sound, so a weaker driver at some frequency pulls the image to the other side. Pure tones are tricky to localise, so treat a wandering image as a hint and confirm it.
Things to try
- Run Auto cycle with your eyes closed and point to where each sound seems to come from.
- Wear the headphones the wrong way round and repeat the left/right check to see a swap.
- Compare the polarity test on headphones and on loudspeakers. The difference is usually much clearer on speakers.
- Play the range sweep in the left ear only, then the right, and compare your marks. Press earbuds gently into the ear to see how the seal changes the bass.
- During the rattle sweep, raise the volume a little (keep it comfortable) to find the level where buzzing starts.
Frequently asked questions
Is this a hearing test?
No. It tests your audio equipment. The frequency marks combine equipment, room and ears, and the page cannot measure absolute levels. If your hearing drops suddenly or you hear ringing, see a doctor the same day.
Why can I not hear the start of the sweep?
Most headphones and nearly all laptop speakers cannot reproduce 20 to 50 Hz, and the ear is very insensitive there. A tone you cannot hear may still be playing.
Why does sound leak to the other side?
With loudspeakers both ears always hear both speakers. With headphones, leaks come from open designs, loose fit, bone conduction or a mono or crossfeed setting on the device.
Does the page alter the sound?
No, but your device might. Turn off spatial sound, loudness, bass boost, mono audio and balance settings, then repeat any test that failed.
Why do the marks differ from run to run?
You press the button after you notice a change, so the mark overshoots. Use the slider and the held tone to refine it.