Overview
ISO 16832:2006 - "Acoustics - Loudness scaling by means of categories" specifies basic, repeatable methods for category loudness scaling used in audiological assessments. The standard defines how to present narrow-band stimuli, train subjects, collect categorical loudness judgements and report results so that loudness functions can be estimated reliably for clinical, research and device‑fitting purposes.
Key topics and technical requirements
- Category loudness scaling: Subjects rate loudness on a category scale (verbal, numeric or symbolic). Recommended boundary categories are “not heard” and “extremely loud” with “medium” as the middle category.
- Response alternatives: Provide a rating scale with finer granularity than the verbal categories; a minimum of 11 response alternatives is recommended. A 51-point numeric scale is suggested for analysis.
- Test signals and timing:
- Use narrow-band signals (filtered noise, warble tones) with bandwidth ≤ one‑third octave.
- Signal duration ≥ 1 s; rise/fall times per IEC 60645‑1.
- Filter slope > 36 dB/octave; ≥ 80 dB/octave advised for steep hearing losses.
- Presentation levels and sequencing:
- At least five distinguishable presentation levels covering the subject’s dynamic range.
- Levels should be pseudo‑randomized and cover the full auditory sensation field (commonly tested at 500 Hz, 1 kHz, 2 kHz and 4 kHz).
- Training / familiarization: A preparatory phase to expose subjects to the full dynamic range before testing.
- Reference values and analysis:
- Reference loudness functions derived from tests on >20 normal‑hearing subjects using median values and interquartile ranges.
- Graphical representation: transform categorical ratings to numeric scale; loudness scale visually comparable to a 50 dB level axis.
- Test environment and equipment: Transducers may be loudspeaker, earphone or cochlear implant; test rooms and equipment must comply with ISO 8253‑1/2 and IEC 60645‑1.
- Reporting: Include subject ID (DOB, sex), examiner, test room, signal types/sequences, presentation levels, responses and graphical outputs.
Applications and who uses it
ISO 16832:2006 is used by:
- Audiologists and clinical audiometric teams for diagnostic loudness profiling and recruitment assessment
- Hearing‑instrument and cochlear‑implant fitters to optimize gain and compression strategies
- Clinical researchers studying loudness perception and hearing impairment
- Manufacturers of audiological test equipment and software for validating loudness scaling features
Practical benefits include standardized loudness-function estimation, improved comparability across clinics/studies, and more informed device fitting.
Related standards
Keywords: ISO 16832:2006, loudness scaling, category loudness scaling, audiological applications, loudness function, hearing assessment, audiometry, hearing instruments.
