ISO 226-2023 PDF

Full title and description

ISO 226:2023 — Acoustics — Normal equal-loudness-level contours. This International Standard defines combinations of sound pressure level and pure-tone frequency that are perceived by young, otologically normal human listeners as equally loud, and provides the data both graphically and numerically for standard one-third-octave centre frequencies.

Abstract

The standard specifies equal-loudness contours under defined conditions (free progressive plane wave, frontal incidence, pure tones, binaural listening, measurement point at the position of the centre of the listener’s head in the absence of the listener) for listeners aged 18–25 years who are otologically normal. Data are given in graphical form (Annex A) and numerical form (Annex B) for preferred one-third-octave frequencies from 20 Hz to 12 500 Hz in accordance with ISO 266.

General information

• Status: Published.
• Publication date: 29 March 2023 (Edition 3, 2023-03).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 13.140 (Noise with respect to human beings).
• Edition / version: Edition 3 (ISO 226:2023).
• Number of pages: 20 pages.

Scope

ISO 226:2023 provides standardized equal-loudness-level contours: combinations of sound pressure level and pure-tone frequency that are perceived as equally loud under specified free-field, frontal-incidence, binaural listening conditions. The standard is intended for use where reference equal-loudness data are required (research, calibration, audio product development and acoustic assessments) and gives the data both graphically and numerically for the preferred one-third-octave frequencies from 20 Hz to 12 500 Hz (per ISO 266).

Key topics and requirements

• Definition and presentation of normal equal-loudness-level contours for humans (graphical Annex A and numerical Annex B).
• Test/listening conditions specified: free progressive plane wave, frontal incidence, pure-tone signals, binaural listening, measurement point at centre-head position in absence of listener.
• Reference listener population: otologically normal persons aged 18–25 years inclusive.
• Frequency coverage and resolution: preferred one-third-octave centre frequencies from 20 Hz to 12 500 Hz in accordance with ISO 266.
• Intended uses: psychoacoustic research, calibration references, product and measurement method development, hearing and noise assessment.

Typical use and users

Primary users are audio and acoustic engineers, psychoacoustics and hearing researchers, hearing-conservation and audiology professionals, loudspeaker and headphone designers, metrology and standards bodies, and test laboratories that need standardized equal-loudness reference data for calibration, design, evaluation and research.

Related standards

ISO 226:2023 is often used alongside related ISO standards in acoustics and audiometry, in particular ISO 266 (preferred frequencies / one-third-octave series), the ISO 389 series (reference zeros for audiometric calibration) and ISO 8253 (audiometric test methods / sound-field and pure-tone audiometry). These accompanying standards provide complementary reference frequencies, threshold reference levels and audiometric test procedures.

Keywords

equal-loudness contours; equal-loudness-level; isosonic; loudness contours; psychoacoustics; free-field; binaural; pure tones; ISO 266; audiometric reference; acoustic measurement.

FAQ

Q: What is this standard?

A: ISO 226:2023 is the International Standard that defines normal equal-loudness-level contours — the combinations of pure-tone frequency and sound pressure level that are perceived as equally loud by young otologically normal listeners.

Q: What does it cover?

A: It covers the specification of equal-loudness contours under prescribed listening and measurement conditions (free progressive plane wave, frontal incidence, binaural listening, measurement at the head-centre point in the absence of the listener) and supplies the results graphically and numerically for one-third-octave preferred frequencies from 20 Hz to 12 500 Hz.

Q: Who typically uses it?

A: Users include acoustic and audio engineers, audiologists and hearing researchers, manufacturers of headphones and loudspeakers, test laboratories, and standards and regulatory bodies needing standardized loudness-reference data.

Q: Is it current or superseded?

A: ISO 226:2023 is the current published edition (Edition 3, published 29 March 2023). It replaces and causes the withdrawal of ISO 226:2003.

Q: Is it part of a series?

A: ISO 226 is a standalone International Standard but is commonly used together with related acoustics/audiometry standards (for example ISO 266 for preferred frequencies, the ISO 389 series for audiometric reference zeros, and ISO 8253 for audiometric test methods).

Q: What are the key keywords?

A: Equal-loudness contours, loudness, isosonic, psychoacoustics, free-field, binaural, pure-tone, ISO 266, audiometric reference.