ISO 532-3:2023

Overview

ISO 532-3:2023 - Acoustics - Methods for calculating loudness - Part 3: Moore‑Glasberg‑Schlittenlacher method specifies a computational procedure to estimate the loudness and loudness level of both stationary and time‑varying sounds as perceived by otologically normal adult listeners under defined listening conditions. The method accepts inputs recorded with a single microphone, a head and torso simulator (HATS), or the electrical signal delivered to earphones, and is accompanied by informative source code provided with the standard.

Key Topics

• Moore‑Glasberg‑Schlittenlacher algorithm: Core algorithmic basis for loudness estimation.
• Input and instrumentation: Guidance on single‑mic, HATS, and earphone measurements; references to relevant electroacoustic instrumentation.
• Auditory preprocessing: Transfer functions modelling outer and middle ear effects (free‑field, diffuse‑field, earphone presentation).
• Spectral and excitation analysis: Running short‑term spectrum and short‑term excitation pattern calculations.
• Specific loudness and transformation: Conversion from excitation to specific loudness including cochlear amplifier gain considerations.
• Temporal processing: Short‑term and long‑term loudness computation, smoothing and binaural inhibition.
• Reporting and uncertainty: Data reporting requirements, uncertainty estimation, and verification test signals.
• Supporting material: Informative software and test signals included as annexes for verification and implementation.

Applications

ISO 532-3:2023 is practical for any application requiring objective estimates of perceived loudness without fresh human observer tests. Typical uses include:

• Audio and product design: loudness evaluation for consumer electronics, loudspeakers, headphones and earphones.
• Environmental and industrial acoustics: assessment of noise sources, impact sounds (e.g., gunshots, sonic booms), and workplace noise.
• Psychoacoustics and research: modelling perception of tones, speech, music and complex sounds.
• Forensic and defense acoustics: characterizing impulsive sounds and soundscapes.
• Software and measurement tools: developers implementing loudness meters or integrating loudness metrics into audio processing pipelines.

Who would use it: acoustical consultants, audio engineers, researchers, regulatory bodies, and developers of measurement instruments and software.

Related Standards

• ISO 532 series (other parts, e.g., ISO 532-2)
• ISO 226:2003 (equal‑loudness contours)
• ISO 389-7:2019 (reference threshold of hearing)
• IEC 60318-7 (HATS)
• IEC 61672-1 (sound level meter specifications)

Keywords: ISO 532-3:2023, loudness calculation, Moore‑Glasberg‑Schlittenlacher, acoustics standard, short‑term loudness, long‑term loudness, head and torso simulator, earphone measurement.