01Phase 01
1. -6dB Equal Power Downmix
Combines left and right as 0.5 × (L + R), lowering each channel by 6 dB so the summed signal cannot clip, and exports a single-channel mono WAV.
Channel Isolation · Phase Inverter (Ø) · 100% Free
Convert Stereo to Mono & Fix One-Sided Audio Online
Fix amateur microphone recordings where sound is only in the left or right ear. Downmix stereo channels with equal -6dB power, isolate single channels, or flip phase polarity (180°).
Stereo to Mono Converter
Runs locally in your browserReady
Drop an audio or video file here
WAV, MP3, M4A, FLAC, OGG, MP4, MOV or WebM. Decoded in your browser, never uploaded.
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100% browser-local processing · No files uploaded to any server
Acoustic Engineering Guide · Architecture
How this tool works in browser memory
How this tool decodes, analyzes, and masters your dialogue locally with zero cloud latency.
02Phase 02
2. Channel Isolation & Repair
Use only the left or only the right channel to rescue one-sided lavalier or shotgun mic recordings. The mono file plays in both ears.
03Phase 03
3. Phase Polarity Inversion (Ø)
Flip the right channel 180° before mixing to fix cancellation when one channel was recorded with reversed polarity.
Connected finishing workflows
Explore companion utilities for dialogue cleanup, speech pacing, and mastering.
Audio Standards & Research
Engineering guides & deep-dive workflows
Explore the acoustic principles, ITU-R loudness standards, and pacing techniques behind this tool.
Phase Cancellation7 min read
How to Fix Phase Cancellation When Converting Stereo Audio to Mono
Why summing out-of-phase stereo tracks destroys vocal presence. Diagnose comb filtering, apply 180° polarity inversion (Ø), and isolate dominant channels.
Mono vs Stereo6 min read
Mono vs Stereo for Spoken Word: How to Choose the Right Export
Why single-voice spoken word belongs in mono. How to downmix stereo recordings, avoid phase cancellation comb filtering, and save 50% bandwidth.
Voice Memo Cleanup7 min read
How to Clean Up Interview Audio Recorded on a Smartphone or Voice Memo
Fixing common phone recording defects: counteracting aggressive AGC pumping, cutting 100Hz boxy resonance, and downward room expansion.
Frequently Asked Questions
Common Questions & Technical Clarifications
How do I fix a recording where sound only plays in my left headphone ear?+
Choose "Left channel only". AutoSilenceCut exports a mono WAV made from the left channel, which plays in both ears.
Why does simple stereo-to-mono downmixing often clip or distort in other tools?+
If you add Left + Right channels directly ($1.0 + 1.0 = 2.0$), the summed signal will clip by +6 dB. AutoSilenceCut applies -6 dB scaling ($0.5 imes (L + R)$) to preserve dynamic headroom without clipping.
What does Phase Invert (Ø) do?+
When two microphones record the same speaker, slight physical distance differences can cause sound waves to arrive out of phase, canceling out vocal low-end. Inverting polarity flips the waveform 180 degrees, which can restore lost low end. In this tool, the toggle flips the right channel before the two channels are mixed.
Is my audio uploaded to any server?+
No. All channel splitting, downmixing, and phase calculations execute 100% inside your browser via the Web Audio API.