ISO 2969:2015

Overview

ISO 2969:2015 - Cinematography - specifies the measurement methods and the characteristic electro-acoustic frequency response of the B‑chain used in motion‑picture dubbing theatres (mixing rooms), screening rooms, and indoor theatres with a room volume greater than 125 m3. The standard is intended to standardize monitoring and reproduction of motion‑picture sound so perceived loudness and frequency response are consistent from installation to installation and across listening positions within a room. It applies to the B‑chain (from the input source audio selector to the listening area) and does not cover the A‑chain (transducer to source selector).

Key topics and technical requirements

• Scope & definitions: Clarifies A‑chain vs B‑chain, pink noise, wide‑range tracks, Curve‑X (X‑Curve) and Curve‑N.
• Measurement method:
  • Use wide‑band pink noise as the test signal and compute a spatial and temporal average of SPL in 1/3‑octave bands.
  • Measure at principal listening positions (mixing personnel, producer) or a set of positions that reduce position‑to‑position response standard deviation to < 3 dB (typically four positions for screening rooms/theatres).
  • Microphone height: seated ear height between 1.0 m and 1.2 m; maintain minimum distances from seats, walls, and screen loudspeakers per the standard.
  • Test level: a single loudspeaker SPL of 85 dB C‑weighted (slow) is a suitable target for measurements.
  • Background noise must be at least 10 dB below the test signal in each 1/3‑octave band (corrections allowed per ANSI/ASA S1.13 when between 4–10 dB).
• Frequency response targets:
  • Provides a characteristic B‑chain response (the X‑Curve) for medium‑sized theatres (typical tolerances ±3 dB per band) and guidance for modifying the curve for smaller/larger rooms and surround arrays.
  • Low‑frequency effects (LFE): soundtrack bandwidth 5 Hz–120 Hz; desirable linear subwoofer response roughly 25 Hz–120 Hz, flat to within ±3 dB after EQ.
• Channel measurement: Measure each channel/bank (screen left/centre/right, surrounds, subwoofer) individually and adjust equalization as necessary.

Practical applications & users

Who will use ISO 2969:2015:

• Audio engineers and dubbing/mixing stage technicians aligning B‑chain playback for motion pictures.
• Cinema sound installers and integrators commissioning screening rooms and indoor theatres.
• Acoustic consultants and facility designers validating room performance.
• Quality assurance teams in post‑production and digital cinema operations.

Practical use cases:

• Verifying consistent monitoring conditions across multiple mixing stages or cinemas.
• Commissioning speaker equalization and subwoofer tuning to meet the X‑Curve and LFE requirements.
• Troubleshooting loudness or tonal inconsistencies between installations.

Related standards and references

• ISO 2969 is intended to be used alongside standards covering the A‑chain and other cinema audio topics.
• Subwoofer guidance: ISO 22234:2005 referenced for subwoofer adjustment.
• Background noise correction methods: ANSI/ASA S1.13.

Keywords: ISO 2969:2015, B‑chain electro‑acoustic response, motion‑picture control rooms, indoor theatres, measurement methods, frequency response, pink noise, X‑Curve, subwoofer tuning.