Audio channels determine how many independent audio streams are in a file. Mono (monaural) has one channel — the same audio signal plays through both speakers or headphone ears. Stereo has two channels (left and right) — different signals can be placed at different positions in the stereo field, creating spatial audio that sounds natural and immersive for music.
File size: stereo files are roughly twice the size of mono at the same bitrate (two channels = twice the data). For voice recordings (podcasts, voice memos, interviews), mono is usually the right choice — voices don't benefit from stereo separation, and mono recordings played on stereo systems sound perfectly natural. For music, stereo is essential for the spatial mix.
Practical guidance: podcast episodes → mono at 128 kbps (approximately 1MB/minute); music releases → stereo at 192 kbps minimum; ringtones → mono at 64 kbps; voice memos for sharing → mono at 64-96 kbps. Converting stereo to mono for voice content halves the file size with no perceptible quality loss. FileCurve's Ringtone Maker outputs optimized mono audio for phone ringtones.