EN ISO 266:1997

Acoustics - Preferred frequencies (ISO 266:1997)

Akustik - Normfrequenzen (ISO 266:1997)

Diese internationale Norm gibt Norm frequenzen für akustiche Messungen an. Die Normfrequenzen basieren auf der Normzahlreihe R10 nach ISO 3 und der Referenzfrequenz von 1000 Hz nach ISO 31-7.

Acoustique - Fréquences normales (ISO 266:1997)

La présente Norme internationale prescrit les fréquences normales pour les mesurages acoustiques. Les fréquences normales sont basées sur la série R10 des nombres normaux de l'ISO 3 et la fréquence de référence de 1 000 Hz. Pour la plupart des mesurages acoustiques et la présentation des données, il est recommandé de choisir un espacement des fréquences basé sur un incrément constant en pourcentage, les fréquences d'essai formant alors une série géométrique. Pour certains mesurages acoustiques, l'espacement des fréquences approprié est un incrément constant. La présente Norme internationale traite de séries géométriques et n'est applicable ni aux cas où un incrément constant des fréquences ou tout autre espacement particulier seraient mieux appropriés, ni lorsqu'il peut y avoir de bonnes raisons d'adopter ou de conserver d'autres fréquences. La présente Norme internationale ne traite pas: -- des fréquences utilisées en musique; -- de toutes les fréquences audiométriques; -- d'autres séries que la série R10 de l'ISO 3.

Akustika - Prednostne frekvence (ISO 266:1997)

General Information

• Status: Published
• Publication Date: 30-Apr-1997
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• ICS: 97.200.20 - Musical instruments
• Technical Committee: CEN/TC 211 - Acuostics
• Drafting Committee: CEN/TC 211 - Acuostics
• Current Stage: 9093 - Decision to confirm - Review Enquiry
• Start Date: 01-Jul-2008
• Completion Date: 01-Jul-2008
• Directive: Harmonized Standard305/2011 - Regulation (eu) No 305/2011 of the European Parliament and of the Council of 9 march 2011 laying down harmonised conditions for the marketing of construction products and repealing council directive 89/106/eec
• Directive:

  ---

  Not Harmonized89/106/EEC - Construction products
• Mandate: M/BC/CEN/91/8 - CPD: Protection against noise
• Ref Project: SIST EN ISO 266:1998 - Acoustics - Preferred frequencies (ISO 266:1997)

Relations

• Referred By: EN 61669:2016 - Electroacoustics - Measurement of real-ear acoustical performance characteristics of hearing aids
• Effective Date: 09-Feb-2026
• Referred By: EN 60068-2-57:2000 - Environmental testing - Part 2-57: Tests - Test Ff: Vibration - Time-history method
• Effective Date: 09-Feb-2026
• Referred By: EN 60942:1998 - Electroacoustics - Sound calibrators
• Effective Date: 09-Feb-2026
• Referred By: EN 60068-2-81:2003 - Environmental testing - Part 2-81: Tests - Test Ei: Shock - Shock response spectrum synthesis
• Effective Date: 09-Feb-2026
• Referred By: EN 60942:2003 - Electroacoustics - Sound calibrators
• Effective Date: 09-Feb-2026
• Referred By: EN 60645-1:2017 - Electroacoustics - Audiometric equipment - Part 1: Equipment for pure-tone and speech audiometry
• Effective Date: 09-Feb-2026
• Referred By: EN 60645-1:2015 - Electroacoustics - Audiometric equipment - Part 1: Equipment for pure-tone audiometry
• Effective Date: 09-Feb-2026
• Referred By: EN IEC 60942:2018 - Electroacoustics - Sound calibrators
• Effective Date: 09-Feb-2026
• Referred By: EN 60500:2017 - Underwater acoustics - Hydrophones - Properties of hydrophones in the frequency range 1 Hz to 500 kHz
• Effective Date: 09-Feb-2026
• Referred By: EN 61669:2001 - Electroacoustics - Equipment for the measurement of real-ear acoustical characteristics of hearing aids
• Effective Date: 09-Feb-2026
• Referred By: EN 61606-1:2004 - Audio and audiovisual equipment - Digital audio parts - Basic measurement methods of audio characteristics - Part 1: General
• Effective Date: 09-Feb-2026
• Referred By: EN 15461:2008+A1:2010 - Railway applications - Noise emission - Characterisation of the dynamic properties of track sections for pass by noise measurements
• Effective Date: 28-Jan-2026
• Referred By: CEN/TR 16891:2016 - Railway applications - Acoustics - Measurement method for combined roughness, track decay rates and transfer functions
• Effective Date: 28-Jan-2026
• Referred By: EN 16286-2:2023 - Railway applications - Gangway systems between vehicles - Part 2: Acoustic measurements
• Effective Date: 28-Jan-2026
• Referred By: EN ISO 10534-1:2001 - Acoustics - Determination of sound absorption coefficient and impedance in impedances tubes - Part 1: Method using standing wave ratio (ISO 10534-1:1996)
• Effective Date: 28-Jan-2026

Overview

EN ISO 266:1997 Acoustics - Preferred Frequencies is an international standard developed by ISO and adopted by CEN, specifying preferred frequencies for acoustical measurements. The standard establishes a series of frequencies, unified around a reference frequency of 1,000 Hz, facilitating consistency in acoustical data collection, analysis, and presentation. By standardizing frequency intervals, EN ISO 266:1997 supports comparability across different instruments, laboratories, and industries.

The preferred frequencies are derived from the R10 series of preferred numbers (see ISO 3) and provide a geometric series based on a constant percentage increment. This standard is foundational for ensuring that measurements and data in acoustics are streamlined, reliable, and universally recognized.

Key Topics

• Reference Frequency: 1,000 Hz is the reference point for all preferred frequencies.
• Geometric Series: The preferred frequencies follow a geometric progression using the R10 series, which relates closely to acoustic measurement needs.
• Frequency Intervals: Covers one-octave and one-third-octave band intervals, facilitating standardized measurements.
• Extension of Series: The specified frequency series can be extended upward or downward by factors of ten.
• Compatibility: While the R10 series is primary, the standard acknowledges the use of base-two (octave-based) series in some applications.
• Precision: Provides both rounded and calculated frequencies (to five significant digits), allowing for accuracy where required.
• Exclusions: Does not standardize frequencies for music, all audiometric frequencies, or series other than R10.

Applications

Adherence to EN ISO 266:1997 offers practical value across a range of industries by:

• Acoustic Measurement: Instrument calibration, environmental noise measurement, and research all benefit from consistent frequency selection.
• Design and Manufacture: Equipment such as sound level meters, microphones, and noise meters are often designed to measure these standard frequencies, ensuring interoperability.
• Noise Abatement: Regulatory noise monitoring and abatement programs rely on standardized frequencies for compliance reporting and comparison.
• Product Testing: Manufacturers testing the acoustical properties of products, such as loudspeakers or headphones, use these preferred frequencies for benchmarking and quality control.
• Educational Use: Provides a foundational reference for acoustics education, ensuring students and professionals are trained using internationally recognized parameters.

Related Standards

For best practices in acoustic measurements and further interoperability, the following standards are closely related:

• ISO 3:1973, Preferred numbers - Basis for the R10 series used in EN ISO 266:1997.
• ISO 31-7:1992, Quantities and units - Part 7: Acoustics - Referenced for definitions and units related to frequencies.
• IEC 1260:1995, Electroacoustics - Octave-band and fractional-octave-band filters - Specifies additional preferred frequencies for other fractional intervals.

By following EN ISO 266:1997, organizations ensure their acoustic measurements, data presentations, and equipment are aligned with international best practices, supporting reliable results, regulatory compliance, and effective communication within the global acoustics community.

Keywords: EN ISO 266:1997, preferred frequencies, acoustics standard, frequency series, R10 series, acoustic measurements, octave bands, standardized frequencies, CEN, ISO 266, acoustic instrumentation.

Standards Content (Sample)

SLOVENSKI STANDARD
01-avgust-1998
Akustika - Prednostne frekvence (ISO 266:1997)
Acoustics - Preferred frequencies (ISO 266:1997)
Akustik - Normfrequenzen (ISO 266:1997)
Acoustique - Fréquences normales (ISO 266:1997)
Ta slovenski standard je istoveten z: EN ISO 266:1997
ICS:
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL
STANDARD
Second edition
1997-04-01
~ ~~
Acoustics - Preferred frequencies
- FrGquences nor-males
Acoustique
Reference number
IS0 266:1997(E)
IS0 266: 1997(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for which
a technical committee has been established has the right to be represented
on that committee. International organizations, governmental and non-
governmental, in liaison with ISO, also take part in the work. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 266 was prepared by Technical Committee
ISO/TC 43, Acoustics.
This second edition cancels and replaces the first edition (IS0 266:1975),
which has been technically revised.
Annex A of this International Standard is for information only.
0 IS0 1997
All rights reserved. Unless othewise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-1211 Geneve 20 l Switzerland
Internet central @ iso.ch
x.400 c=ch; a=400net; p=iso; o=isocs; s=central
Printed in Switzerland
IS0 266:1997(E)
0 IS0
Introduction
This International Standard specifies a series of preferred frequencies in
order to provide a common basis for comparing the results of acoustical
measurements.
The frequency series is referred to the reference frequency of 1 000 Hz,
which is also the reference frequency for the definition of the phon (see
IS0 31-7).
The specification of the preferred frequency series reduces to a minimum
the number of frequencies at which acoustical data need to be tabulated.
Also measurement equipment may be specifically constructed for these
frequencies.
The specified series of preferred frequencies uses powers of IO and is
therefore especially convenient for extensions into the infrasonic and
ultrasonic (frequency) ranges. Another series of frequencies that is in use is
based on the definition of the octave as the frequency ratio 1:2. The
frequencies of this series are calculated as powers of two (IEC 1260 base-
two series).
Strictly, these two series are incompatible. However the base-two series
may be accepted as a sufficient approximation to the base-ten series
because of the fact that 21i3 = 1,259 9. is very near y the same as
1O1 ’1o = 1,258 9.
Practical considerations make some additional rounding desirable: Thus
500 Hz is listed instead of 501 ,187 233. . Hz, which is the exact frequency
from the base-ten series. The calculated value of the exact frequency
expressed to five significant figures is given in the second column of
table 1. In this way, the maximum individual deviation, in the frequency
range 20 Hz to 20 000 Hz, between t
...