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I NT ERN AT I O NA I. O RG A N IZAT I O N FO R STA N DA R D I Z AT1 O N
IS0 R ECOM MEN DATI O N
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R 31
PART VI1
QUANTITIES AND UNITS OF ACOUSTICS
1st EDITION
November 1965
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COPYRIGHT RESERVED
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 Denmark
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 31, Part VII - Quantities and Units of Acoustics, was
drawn up by Technical Committee ISO/TC 12, Quantities, Units, Symbols, Conver-
sion Factors and Conversion Tables, the Secretariat of which is held by the Danish
Standards Association, Dansk Standardiseringsrhd (DS).
Work on this question by the Technical Committee began in 1956 and led, in 1960,
to the adoption of a Draft IS0 Recommendation.
It should be noted that the following international organizations have had these
draft proposals sent to them and have taken part in the discussions at the meetings
of Technical Committee ISO/TC 12:
O
International Committee on Weights and Measures,
International Electrotechnical Commission,
International Union of Pure and Applied Chemistry,
International Union of Pure and Applied Physics
and its Sub-Committee SUN,
International Commission on Illumination,
Comité International de mktrologie légale,
World Meteorological Organization,
International Commission on Radiological Units and Measurements,
International Telegraph and Telephone Consultative Committee.
In June 1961, this Draft IS0 Recommendation (No. 440) was circulated to all the
IS0 Member Bodies for enquiry. It was approved, subject to some modifications
of an editorial nature, by the following Member Bodies:
Australia Hungary Poland
Austria India Portugal
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Belgium Ireland Romania
Canada Israel Sweden
Switzerland
Chile Italy
Czechoslovakia Japan U. A. R.
Mexico United Kingdom
Denmark
France Netherlands U. S. A.
U. S. S. R.
Germany New Zealand
Norway Yugoslavia
Greece
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 RECOMMEN-
DATION.
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P
Introduction
General remarks
This document, containing a table of Quantities und Units of Acoustics, is part of a more compre-
hensive publication dealing with quantities and units in various fields of science and technology.
Other part of this more comprehensive publication are at present
IS0 Recommendations R 31,
Part I (2nd edition) : The International System of Units und Quantities und Units of Space und Time1),
Part II : Quantities and Units of Periodic und Related Phenornenu,
Quantities und Units of Mechanics,
Part III :
Part IV : Quantities und Units of Heat,
Part V: Quantities und Units of Electricity und Magnetism,
Part XI : Muthemuticul Signs und Symbols for Use in Physicul Sciences and Technology.
General information regarding the arrangement of the tables and the symbols and abbreviations
used is to be found in the introduction to ISO/R 31/Part I, where the full definitions of funda-
mental units are given as an appendix.
The statements in the definition columns for quantities are given merely for identification, they are
not intended to be complete definitions.
Special remarks
The explanations in the definition columns for quantities presuppose in general linear systems.
When it is necessary to use subscripts to avoid confusion between similar symbols in different
domains, the subscript “a” is recommended for the acoustical case.
The preference given to the units of the International System of Units has been indicated by placing
them first.
l) The title of the first edition of this document was: “Fundamental Quantities and Units of the MKSA System and Quantities
and Units of Space and Time”.
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7. Acoustics
Quantities
7-1 .I . . . 7-16.1
-
Item
Quantity
Symbol ')
Definition Remarks
No.
-
7-1 .I period, T
Time of one cycle.
periodic time
7-2.1 frequency
Concerning the standard tu
quency (standard musical pitcl
lSO/R 16-1955.
7-3.1 frequency interval
The frequency interval between two
'requencies is the logarithm to a speci-
9ed base of the ratio between them.
~ ___-
7-4.1 angular frequency, 0=27Cf
circular frequency
7-5.1 wavelength A
3
7-6.1 circular wave number k ZX
k=-
a
density (mass density) Mass divided by volume.
7-7.1
e
- -
Pressure that would exist with no sound
7-8.1 static pressure
P.
waves present.
7-8.2 (instantaneous) sound The difference between the instanta-
P
pressure neous pressure and the static pressure.
The root mean square value of
tities 7-8.2, 7-9.1, 7-10.1, 7.
Instantaneous displacement of particle
7-9.1 (instantaneous) sound par-
7-12.1 are often called "effecth
ticle displacement of the medium from its mean position.
and the same symbols are c
without modification to denc
7-1 O.' (instantaneous) sound par-
at
fective values.
!l= --
ticle velocity
at
-
au
7-1 1 .' (instantaneous) sound par- a
as-
ticle acceleration
at
>
7-1 2.' (instantaneous) volume Instantaneous rate of volume flow due
velocity to sound wave across an area.
Velocity of propagation of sound wave.
7-13: velocity of sound C
Mean sound energy in a given volume If the energy density is var
7-1 4.' sound energy density E
time, the mean must be take
divided by that volume.
interval during which the s(
be considered statistically st
Sound energy transferred in a certain
7-1 5. sound energy flux,
time interval, divided by the duration
sound power
of that interval.
For unidirectional sound energy flux,
sound intensity
7-1 6. I, J
sound energy flux through an area
normal to the direction of propagation
divided by that area.
-
nplete definitions.
ication and they are not intended to be
I The tatements in this column are given merely for ide
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7. Acoustics
Units
7-1 .a . . . 7-16.b
-
I
Name of unit
International
Item and in certain
symbol Definition Conversion factors
Remarks
No. cases abbreviation
for unit
for this name
7-1 .a second
S See 0-3. *)
7-2.a hertz Hz 1 Hz is the frequency c
1 HZ = 1 S-‘
a periodic phenomenon c
...