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INTERNATIONAL ISO
STANDARD 80000-8
Second edition
2020-02
Quantities and units —
Part 8:
Acoustics
Grandeurs et unités —
Partie 8: Acoustique
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Remark on the use of the symbols lb and lg . 1
Bibliography . 8
Alphabetical index . 9
Foreword
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This document was prepared by Technical Committee ISO/TC 12, Quantities and units, in collaboration
with IEC/TC 25, Quantities and units.
This second edition cancels and replaces the first edition (ISO 80000-8:2007), which has been
technically revised.
The main changes compared to the previous edition are as follows:
— the table giving the quantities and units has been simplified;
— some definitions and the remarks have been stated physically more precisely.
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Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv © ISO 2020 – All rights reserved
INTERNATIONAL STANDARD ISO 80000-8:2020(E)
Quantities and units —
Part 8:
Acoustics
1 Scope
This document gives names, symbols, definitions and units for quantities of acoustics. Where
appropriate, conversion factors are also given.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
Names, symbols, definitions and units for quantities used in acoustics are given in Table 1.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
sound particle
material element
smallest element of the medium that represents the medium’s mean density
[SOURCE: ISO 18405:2017, 3.1.1.5, modified - Note 1 to entry deleted.]
4 Remark on the use of the symbols lb and lg
In accordance with ISO 80000-2, the abbreviations lb and lg are used to indicate logarithms to the base
2 (log ) and base 10 (log ), respectively.
2 10
2 © ISO 2020 – All rights reserved
Table 1 — Quantities and units used in acoustics
Item No. Quantity Unit Remarks
Name Symbol Definition
8-1 logarithmic G quantity given by: oct One octave (oct) is the logarithmic frequency
frequency range range between f and f when
1 2
f f dec
2 2
G==lb octdlg ec
f
f f
=2 . Similarly, one decade (dec) is the
1 1
f
where f and f are two frequencies (ISO 80000-3)
1 2
logarithmic frequency range between f and f
1 2
when
f
=10 ; thus 1 dec = (lb 10) oct ≈ 3,322 oct.
f
ISO 266 specifies preferred frequencies for
acoustics separated by logarithmic frequency
ranges equal to one tenth of a decade (0,1 dec).
Each 0,1 dec logarithmic frequency range is
referred to in ISO 266 as a "one-third-octave
interval" because 0,1 dec is approximately equal
to 1/3 oct. Similarly, a logarithmic frequency
range of 0,3 dec is referred to as a "one-octave
interval" because 0,3 dec is approximately equal
to 1 oct.
A logarithmic frequency range equal to one tenth
of a decade can be referred to as a decidecade.
8-2.1 static pressure p pressure (ISO 80000-4) in a medium when no Pa This definition applies to a medium with zero
s
sound wave is present flow.
-1 -2
kg m s
8-2.2 sound pressure p difference between instantaneous total pressure Pa
and static pressure (item 8-2.1)
−1 −2
kg m s
8-3 sound particle δ vector (ISO 80000-2) quantity giving the instan- m
displacement taneous displacement (ISO 80000-3) of a particle
in a medium from what would be its position in
the absence of sound waves
−1
8-4 sound particle u, (v) vector (ISO 80000-2) quantity given by: m s The definition is limited to small-amplitude
velocity acoustic disturbances such that the magnitude
∂δδ
of u is small relative to the phase speed (ISO
u=
∂t
80000-3) of sound.
where δ is sound particle displacement (item 8-3)
and t is time (ISO 80000-3)
Table 1 (continued)
Item No. Quantity Unit Remarks
Name Symbol Definition
−2
8-5 sound particle a vector (ISO 80000-2) quantity given by: m s The definition is limited to small-amplitude
acceleration acoustic disturbances such that the magnitude
∂u
of the sound particle velocity is small relative to
a=
∂t
the phase speed (ISO 80000-3) of sound.
where u is sound particle velocity (item 8-4) and
t is time
3 −1
8-6 volume velocity q, q surface integral of the normal component of m s
v
the sound particle velocity (item 8-4) over a
volume flow rate
defined surface
8-7 sound energy density w quantity given by: J/m This definition can become inapplicable in situa-
tions with a high mean fluid flow.
−1 −2
kg m s
1 1 p
wu=+ρ
m
2 2
ρ c
m
where ρ is mean density (ISO 80000-4), u is the
m
magnitude of the sound particle velocity (item
8-4), p is sound pressure (item 8-2.2), and c is the
phase speed (ISO 80000-3) of sound
8-8 sound energy Q integral of sound energy density (item 8-7) over a J The sound energy in region R can be ex-
specified volume pressed by:
2 −2
kg m s
Qw= ()xxd
∫
R
where d x is an element of volume.
8-9 sound power P, W integral over a surface of the product of sound W This defi
...