Monaural Sound

单声道 (Monaural Sound, Mono) is a method of representing an entire program using a single audio channel. All sound sources are mixed into a single signal, and the bitstream does not preserve left-right differences; this signal can be sent to a single speaker or to multiple speakers simultaneously, and the number of speakers does not convert the program into stereo.

单声道 was widely used in early records, radio broadcasts, movies, and portable recordings. Two-track or multi-track recordings can also be ultimately mixed down to 单声道; therefore, the “number of recording tracks” and the “number of release channels” are not the same concept. Dialogue, commentary, or older recordings in modern releases may still retain 单声道.

Copying 单声道 to both the left and right channels is commonly referred to as dual 单声道. If two digital channels have exactly the same sample data, the perceived sound will still form a single sound image centered between them; if the two channels carry different languages or separate programs, this constitutes a dual-channel dual 单声道, rather than a stereo mix.

When remastering historical recordings, the left and right channels on the tape or record may contain different levels of noise and phase errors. Correlation must be checked before merging, as simply adding the channels together may cancel out part of the signal. A file marked as 1.0 only indicates the final channel configuration; it does not provide information about the original recording equipment or production process.