Audio recorded live on set during the camera take, as opposed to ADR or studio dubbing in post.
Technical Details
Modern location sound recorders operate with signal-to-noise ratios of at least 120 dB and support up to 32 simultaneous channels. Shotgun microphones with a directional pattern of 60-90° are typically used, while lavalier microphones utilize transmission frequencies between 2.4 GHz and 7.1 GHz. Recording is done on CF cards or SSDs with data rates of 4.6 MB/s per channel at 48kHz/24-bit. Windscreen systems reduce wind noise by up to 25 dB, while isolation mounts dampen footstep noise by 15-20 dB.
History & Development
The first documented use of location sound occurred in 1929 on Alfred Hitchcock's "Blackmail," where the technique was initially limited to optical soundtracks. In 1958, the Nagra III revolutionized the industry with battery-powered 6.35mm tape recording with crystal sync. The introduction of DAT recorders in 1987 and digital multitrack systems from 1995 onwards enabled lossless recording with timecode synchronization for the first time. Since 2010, file-based workflows with 32-bit float recording for extended post-production have dominated.
Practical Application in Film
On "Das Boot" (1981), Milan Bor recorded all dialogue within the authentic submarine, creating the characteristic claustrophobia and metal resonance. "Gravity" (2013) combined minimal location recordings of breathing sounds with complete studio post-production for the space sequences. The typical workflow includes pre-roll recording 5 seconds before "Action," continuous room tone recording between takes, and separate wild track sessions for atmosphere. Location recordings account for 70-90% of the final dialogue track but reduce post-production costs by an average of 30%.
Comparison & Alternatives
Location sound differs from ADR (Automated Dialogue Replacement) through natural room acoustics and the authentic vocal cadence of the actors. Foley recordings replace specific sound effects, while location sound preserves the overall atmosphere. In extreme shooting conditions such as action sequences or with historical costumes, a 50/50 mix of location and studio sound is deliberately employed. Modern AI-based noise reduction has, since 2020, made it possible to salvage previously unusable location recordings with noise levels up to -6 dB below the signal level.