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UDC 534
IS0
I N T ER N AT I ON A L O RG A N I ZAT I O N FOR STA N DA RD I Z AT I O N
IS0 R E CO M M EN DATI O N
R 454
RELATION BETWEEN SOUND PRESSURE LEVELS
OF NARROW BANDS OF NOISE
IN A DIFFUSE FIELD AND IN A FRONTALLY-INCIDENT FREE FIELD
FOR EQUAL LOUDNESS
1st EDITION
November 1965
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The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 454, Relation Between Sound Pressure Levels of Narrow
Bands of Noise in a Diffuse Field and in a Frontally-Incident Free Field for Equal Loudness,
was drawn up by Technical Committee ISO/TC 43, Acoustics, the Secretariat of which is
held by the British Standards Institution (BSI).
to IS0 Recommendation
This IS0 Recommendation R 454 is a SUPPLEMENT
R 226, Normal Equal-Loudness Contours for Pure Tones and Normal Threshold of Hearing
under Free-Field Listening Conditions, 1st Edition-1961.
Work on this question by the Technical Committee began in 1960 and led, in 1963, to
the adoption of a Draft IS0 Recommendation.
In December 1963, this Draft IS0 Recommendation (No. 699) was circulated to all the
IS0 Member Bodies for enquiry. It was approved by the following Member Bodies:
Australia Finland Netherlands
Austria France New Zealand
Belgium Germany Sweden
Brazil Switzerland
Greece
Canada Hungary United Kingdom
Chile India U.S.A.
Colombia Italy U.S.S.R.
Czechoslovakia Japan Yugoslavia
Denmark Korea, Rep. of
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in November 1965, to accept it as an IS0 RECOMMENDATION.
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IS0 / R 454 - 1965 (E)
IS0 Recommendation R 454 November 1965
RELATION BETWEEN SOUND PRESSURE LEVELS
OF NARROW BANDS OF NOISE
IN A DIFFUSE FIELD AND IN A FRONTALLY-INCIDENT FREE FIELD
FOR EQUAL LOUDNESS
Supplement to IS0 Recommendation R 226
NORMAL EQUAL-LOUDNESS CONTOURS FOR PURE TONES
AND NORMAL THRESHOLD OF HEARING
UNDER FREE-FIELD LISTENING CONDITIONS
FOREWORD
Curves defining relations between frequencies characterizing sound and their sound pressure
levels for the condition of constant loudness, i.e. equal-loudness contours, are involved in many
aspects of subjective acoustics. They are fundamental to a proper understanding of the functioning
of the human ear in the perception of loudness. They also have important practical applications,
for example, in the development of methods of computing loudness from the physical properties
of sounds.
Types of sounds and the manner in which they arrive at a listener may be varied. In addition to
the basic equal-loudness contours for pure tones, as specified in IS0 Recommendation R 226,*
it is desirable to establish equal-loudness conto
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