Decibel Shield
Tone generator › Left and right audio test
Left and right audio test for headphones and speakers
Play a tone routed to one channel at a time and say which side you heard it from. Because the test asks which side rather than whether you heard anything, it can tell working headphones or speakers from swapped channels, a dead side or a mono downmix. Two more steps check that both sides play at the same level and with the same polarity, and two sweeps check the stereo image and the frequency range.
1 Left channel
This tone is routed to the left channel only. Which side did you hear it from?
2 Right channel
This one is routed to the right channel only. Which side did you hear it from?
3 Balance
The same 440 Hz tone at the same level in both channels. It should sit in the middle of your head, or halfway between the speakers. Where did it sit?
4 Phase (polarity)
Two 300 Hz tones. In tone A both sides push together; in tone B the right side is flipped. Correctly wired gear makes A sound focused in the middle and B sound wide or hollow. Which one sounded more focused?
5 Stereo image
A 500 Hz tone that travels from the left ear to the right over eight seconds. It should cross smoothly through the middle of your head, not jump from one side to the other.
6 Frequency range
One tone gliding from 20 Hz to 20 kHz over 12 seconds. Note when it fades in at the bottom and when it disappears at the top: the low end is your drivers, the top end is your drivers and your ears.
Tones play out through your speakers or headphones. There is no microphone here, nothing is recorded, and the output level is capped, though you should still start with the volume low.
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What each result means
| Left tone heard from | Right tone heard from | What it means |
|---|---|---|
| Left | Right | Both channels work and the stereo image is the right way round. |
| Right | Left | Swapped channels. Check the headphones are not on backwards, then the player, the adapter and the cable. |
| Nothing | Right | The left side is not producing sound. Usually the cable or the connector rather than the driver. |
| Left | Nothing | The right side is not producing sound, for the same reasons. |
| Both | Both | Something is summing the channels: a mono accessibility setting, a mono Bluetooth device, or an adapter that shorts them together. |
| Nothing | Nothing | No audio is arriving at all. Check volume, output device, mute switches, and whether another app has the device. |
Testing speakers instead of headphones
Sit centred between the two speakers, about as far from each as they are from each other, and keep the volume moderate. The left and right steps work exactly as on headphones. Balance and phase matter more on speakers: a speaker further away or angled off-axis pulls the centre tone sideways, and a speaker with its + and - wires swapped sounds thin in the bass and loses the centre of every voice. For a 5.1 or 7.1 system, the surround sound test plays each speaker on its own, including the centre and the subwoofer.
Why "which side" and not "did you hear it"
A test that only asks whether you heard something passes a pair of headphones with the channels reversed, because both tones were audible. Reversed channels are common and easy to miss: nothing sounds broken, but the stereo image is inside out, instruments sit on the wrong side, and anything mixed to move across the field moves the wrong way. Asking which side each tone came from turns that into a finding in two clicks.
If the tones are fine but your headphones sound wrong
Channel routing is the one thing this test can settle definitively. If both sides work and sit correctly, the next things to check are the low end and the top end, which are where cheap drivers and worn ones actually fail. The bass test steps from 20 Hz to 200 Hz so you can find the lowest note your headphones really reproduce, and the tone generator runs the whole range up to 20 kHz. If the problem is your microphone rather than your headphones, use the mic test.
Volume, and one real risk
Pure tones carry all their energy at a single frequency, so they sound quieter than music at the same measured level and tempt you to turn the volume up. The output here is capped and every tone stops itself after four seconds, but start low all the same. If you want to know what level you are actually listening at, our headphone volume guide covers the numbers, and the decibel meter can read the room around you.
How do I test whether my left and right headphones are correct?
Play a tone routed to one channel at a time and note which side you actually hear it from, which is what the test above does. If the left-only tone arrives on the right, your channels are swapped. If it arrives on both sides, something is downmixing to mono. If it arrives on neither, that side is not producing sound at all.
My left and right are swapped. What causes that?
Most often the headphones are simply on backwards, since the L and R markings are small and sometimes inside the band. After that, look at a channel-balance or swap setting in your player, an adapter or splitter wired crossed, a worn 3.5 mm jack that is not seated fully, or the audio file itself being mastered with the channels reversed.
Why can I hear a one-sided tone in both ears?
Something between the page and your ears is summing the channels. The common causes are a mono accessibility setting, which macOS and iOS call Mono Audio and Windows lists under Accessibility, a Bluetooth speaker or single earbud that is inherently mono, or a cheap adapter that shorts the two channels together.
One side is completely silent. Is the headphone broken?
Not necessarily, and the cable is a more likely culprit than the driver. Flex the cable near each connector while a tone plays and listen for the sound cutting in and out, try the other end if the cable detaches, and test the same headphones on a different device. If a second pair also loses the same side on that device, the fault is the socket or the sound card.
How do I test left and right speakers?
The same way as headphones. Sit centred between the speakers, play the left-channel tone and say which speaker it came from, then the right. A tone from the wrong speaker means the speaker cables or the amplifier channels are crossed; nothing from one speaker means that speaker, its cable or that amplifier channel. Then run the balance and phase steps, which matter more on speakers than on headphones.
What does the phase test check?
Polarity: whether both drivers push air in the same direction at the same moment. If one speaker has its + and - wires swapped, the two cancel each other in the middle, so voices lose their centre and the bass sounds thin. Tone A plays in phase and tone B with one side flipped; on correctly wired gear A sounds focused and B sounds wide or hollow. If B sounds more focused, one side is reversed.
Why does the centre tone lean to one side?
Less sound is reaching you from the other side. Check the balance setting in your system sound settings first, then a blocked or worn earpiece, a speaker that is further away or pointed elsewhere, and a loose plug. If you swap the headphones round and the lean moves to the other side, the gear is fine and the difference is in your ears, which the online hearing test checks one ear at a time.
Does this test measure sound quality?
No. It plays pure tones and reports what you say you heard, so it can establish which channels produce sound and whether they are the right way round. It cannot judge frequency response, distortion or soundstage, and no browser test can, because there is no calibrated microphone in the loop.
What volume should I use?
Start low and raise it only until the tone is comfortably audible. Pure tones sound quieter than music at the same level, which tempts people to turn them up further than they should, and a sustained tone at high volume is harder on your ears than the same level of music.