The fly moves between your ears in stereo, through the middle of your head. It can't place sound in front of you, behind you or above you, so on its own it is not a 3D sound test. It shows whether both sides work, are balanced and pan smoothly, and with your device's spatial audio on, what that processing adds.
How to use the fly test
Press Play. The fly crosses from ear to ear in about three seconds, back and forth.
To hold it, tap Left or Right, or drag it along the slider. Turn Auto-flight on to let it go.
The ear cards show how loud the fly should be in each ear, not a measurement of your headphones. In the middle both read about 71%, which adds up to the same loudness as one ear at 100%.
How to read the result
It glides smoothly and the middle is centred — stereo works and both sides are balanced.
It doesn't move — the sound is mono: a mono audio setting in accessibility options, a mono adapter, or a Bluetooth headset in hands-free mode (see below).
The middle is off to one side — check the balance slider in your sound settings first.
One side is quieter — swap the headphones round. If the quiet side follows them, they are at fault; if it stays in the same ear, check the fit or the ear tip.
The middle sounds hollow or hard to place — one side may be wired in reverse polarity.
It cuts out or jumps — Bluetooth interference or a loose plug.
It crackles at one end — that driver distorts. Lower the volume and listen again.
It moves the wrong way — left and right are swapped. Confirm with the left-right test.
How to tell if spatial audio is on
Play the fly with spatial audio off, then turn it on. The fly should move out of your head and pass in front of you. If nothing changes, the feature is off or doesn't apply to your browser.
Open Settings › System › Sound and choose your headphones
Under Spatial audio, pick Windows Sonic for Headphones
In Windows 10 it is Spatial sound, in the menu you get by right-clicking the volume icon
Connect your AirPods or Beats
Open Control Center and click the arrow next to them
Choose Spatialize Stereo, then Fixed or Head Tracked
Connect your AirPods or Beats
Open Control Center and touch and hold the volume slider
Tap Spatialize Stereo, then Fixed or Head Tracked
Connect your headphones
Open Settings › Connected devices and tap the gear next to them
Turn on Spatial audio. On Samsung phones it is 360 Audio, under Sound quality and effects
With Head Tracked on, the fly stays put when you turn your head.
FAQ
When an app opens its microphone, Windows switches the headset to hands-free mode: mono and low quality. The fly then stays in the middle. Close that app, or pick the headset's stereo output instead of the hands-free one.
No, the fly is stereo. The speaker test plays each 5.1 or 7.1 channel on its own; with virtual surround on, each should sound in its own place around you.
Yes, with any wired or wireless headphones, in a modern browser on a computer or a phone. A phone's own speakers sit too close together to show the fly move, so connect headphones.