Left / right audio test

A tone in one channel at a time, so you can settle in thirty seconds whether a side is dead or simply wired backwards.

Silent
Left Right

Turn your volume to about a third before you start. Tones are louder than music.

  1. Left channel

    A 440 Hz tone plays in the left speaker only. Sound from the right means the channels are swapped.

  2. Right channel

    The same tone, right side only. Nothing here after a working left usually means a dead driver, a loose plug or a balance slider pushed to one side.

  3. Stereo check

    Left, then right, then both together. The middle pass should sit in the centre of your head on headphones.

Point before you look

The one rule that makes this test reliable: when a tone plays, point at where it came from before you read the screen. Expectation is a powerful thing, and if you already know the page is playing the left channel it is easy to hear it on the left. Point first, then check what the page says.

The third step plays left, then right, then both. That last pass is the one people skip and the one that catches the subtler faults: two channels that both work but are reversed, or a pair that produces sound on both sides at noticeably different levels.

The four things that cause a silent side

A balance control. Every operating system has one, it is rarely visited, and it survives reboots. On Windows it is per-device, under the output device's properties. On macOS it is in Sound, under Output. Check it first, because it costs nothing and explains a genuine share of "broken" headphones.

A plug not fully home. A 3.5 mm jack that is one click short makes contact on some conductors and not others, which usually leaves you with one channel, sometimes a thin distorted sound. Push firmly; most sockets have a definite stop.

A broken cable. Play a continuous tone and flex the cable slowly near the plug, then near the cup. If the sound stutters in time with your hand, the conductor inside is broken. Those two points take nearly all the strain in normal use, which is why nearly all cable failures happen there.

A dead driver. The least common and the only one that costs money. Conclude this only after the same headphones have failed on a second device and the first device has worked with a second pair of headphones. Two swaps, four combinations, and the answer is unambiguous.

When the channels are reversed

On speakers, reversed channels are almost always the cabling at the amplifier: two cables in the wrong pair of terminals. Nothing in software normally does this. Swap them and run the test again.

On headphones, check orientation first, then look for an audio app with a channel swap or a "reverse stereo" mode. Some gaming and virtual-surround utilities offer exactly that, and it is easy to leave on after experimenting.

In a car, reversed front channels are usually a head unit that has been replaced without matching the loom, and the fix is at the adapter rather than in the menu.

What a working result looks like

Left plays on the left, right plays on the right, and the combined pass sounds like it comes from a point in the middle rather than from either side. If you get that, your channel routing is correct and anything still wrong with your sound is elsewhere: the source, the mix, or the response of the hardware.

From here, the full sound test adds the bass and top-end sweeps, the headphone test covers the headphone-specific checks, and the tone generator will hold a tone in one channel for as long as you need while you work on a cable.

Frequently asked questions

How do I test left and right audio?

Play a tone in one channel at a time and point at the side you hear. The test above sends 440 Hz to the left, then the right, then both, and records your answers. Three steps, about thirty seconds.

How do I know if my left and right are swapped?

When the left step plays, point at where the sound came from before you look at the screen. If it came from your right, the channels are reversed. On speakers that is a cable swap; on headphones it is usually the headphones being worn backwards; and occasionally an audio app has a channel-swap option switched on.

Why is only one side working?

Check in this order: the balance control in your system sound settings, the plug fully seated in the socket, the cable flexed near the plug while a tone plays, and finally the same headphones on a different device. Each step is free and each one rules out a whole category.

What is the difference between mono and stereo?

Mono sends one identical signal to both channels, so nothing ever appears to come from one side. Stereo carries two different signals and the difference between them is what places a sound left, right or centre. A device stuck in mono will pass a left/right test that only checks for sound and fail one that checks which side.

My computer only plays mono. How do I fix it?

On Windows, look for the "mono audio" accessibility switch, which is easy to turn on by accident and collapses both channels. macOS, iOS and Android all have the same setting under accessibility. If mono is off and you still hear no separation, the source file may itself be mono.

Does a balance slider affect the test?

Yes, completely. A balance control pushed to one side makes a perfect pair of headphones look like a broken one. It is worth opening the sound settings and confirming it is centred before you spend money on anything.

More audio tools