Audio mixing for film and television is a process during the post-production

Post-production

Post-production is part of filmmaking and the video production process. It occurs in the making of motion pictures, television programs, radio programs, advertising, audio recordings, photography, and digital art...

 stage of a moving image program by which a multitude of recorded sounds are combined into one or more channels. In the process, the source signals' level, frequency content, dynamics and panoramic position are commonly being manipulated and effects such as reverberation

Reverberation

Reverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air...

 might be added.

The process takes place on a mix stage, typically in a studio

Studio

A studio is an artist's or worker's workroom, or the catchall term for an artist and his or her employees who work within that studio. This can be for the purpose of architecture, painting, pottery , sculpture, scrapbooking, photography, graphic design, filmmaking, animation, radio or television...

 or theater, once the picture elements are edited into a final version. Normally the engineer will mix 4 main elements: Speech (dialogue, ADR, Voice-over

Voice-over

Voice-over is a production technique where a voice which is not part of the narrative is used in a radio, television production, filmmaking, theatre, or other presentations...

s, etc.), Ambience

Ambience (sound recording)

In filmmaking, ambience consists of the sounds of a given location or space. It is the opposite of "silence." This term is often confused with presence....

 (or atmosphere), Sound effects, and Music.