Stereo Sound Test
Check left/right channels, alternating stereo, test tones, sweep and local audio files.
Start quiet
Nothing plays until you press a button. Start with the volume low and raise it slowly — short 20 ms fade-ins protect against clicks, not against loud output.
Private by design: every tone is generated inside your browser with the Web Audio API. A file you pick never leaves your device and is only decoded locally.
Channel mode
Alternate switches sides every second. The diagram always shows which channel is sounding right now.
Silent. Press a channel button to play the tone.
Test tone
Logarithmic control from 20 Hz up to your device limit. Presets jump straight to a musical pitch.
Frequency sweep (optional)
Glides from the start frequency to the end frequency once, for at most 10 seconds. It never raises the volume by itself — if you hear nothing at an extreme, do not turn it up to compensate.
Play your own file in a channel
Pick an audio file (up to 20 MB) to hear it through the selected channel mode. Useful for testing music against left, right or alternating output.
A mono speaker, a mono Bluetooth mode or a system mixer can combine both channels: hearing sound on both sides does not prove a channel is broken, and hearing one side on a mono device does not prove the tool failed.
The highest tone is capped by your audio hardware (half the sample rate, up to 20 kHz). No page can make a speaker reproduce frequencies it physically cannot move for.
Sound stops automatically if you hide the tab, and all audio resources are released when you leave the page.
This check listens for channel routing and obvious range gaps. It does not measure frequency response, loudness in dB SPL, headphone quality or your hearing.
Check stereo channels and tones in one minute
- Lower the volume, pick LEFT ONLY and press play: the left speaker or earpiece should answer alone.
- Repeat with RIGHT ONLY on the other side, then BOTH to confirm the centered image.
- Try ALTERNATE L/R and watch the diagram: the active side flips every second.
- Drag the frequency control or tap a preset — 440 Hz is the reference pitch — and confirm the tone follows without clicks or dropouts.
- Optionally run the sweep (5 seconds by default): a smooth glide is normal, sudden silent gaps are worth retesting.
- To test music instead of a tone, pick a local file and replay the same channel modes with it.
Stereo sound test questions
I hear both sides when only LEFT is selected. Is the tool broken?
Probably not: many phones, mono speakers and system mixers combine both channels before output. Retest with wired stereo headphones — if left still leaks into right there, check the balance settings of your system.
The sweep goes silent at the low or high end. Should I turn the volume up?
No. Small speakers physically cannot move enough air for deep bass, and age or hearing limits cut extreme treble. Silence at the extremes is expected; never raise the volume to chase a frequency you cannot hear.
Can these tones damage my headphones or speakers?
No — everything starts quiet at a conservative level with short fade-ins. Keep the volume moderate; the risk at high levels is to your ears, not the hardware.
My file was refused or will not play. What now?
Files over 20 MB, non-audio files and empty files are refused before decoding. If a normal MP3, WAV, OGG or M4A still fails, the file itself is likely corrupt — everything is decoded locally, nothing is uploaded.
Does this test grade my headphones or my hearing?
No. It checks which channel sounds and whether tones follow the controls. It measures no frequency response, no loudness in dB SPL, no headphone quality and no hearing health — a listening check cannot certify any of those.