Sound energy density or sound density is the
sound energy
In physics, sound energy is a form of energy that can be heard by living things. Only those waves that have a frequency of 16 Hz to 20 kHz are audible to humans. However, this range is an average and will slightly change from individ ...
per unit volume. The
SI unit
The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. ...
of sound energy density is the
pascal (Pa), which is 1 kgâ‹…m
−1⋅s
−2 in SI base units or 1
joule
The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applie ...
per
cubic metre (J/m
3).
Mathematical definition
Sound energy density, denoted ''w'', is defined by
:
where
*''p'' is the
sound pressure;
*''v'' is the
particle velocity
Particle velocity is the velocity of a particle (real or imagined) in a medium as it transmits a wave. The SI unit of particle velocity is the metre per second (m/s). In many cases this is a longitudinal wave of pressure as with sound, but it can ...
in the direction of propagation;
*''c'' is the
speed of sound.
The terms instantaneous energy density, maximum energy density, and peak energy density have meanings analogous to the related terms used for sound pressure. In speaking of average energy density, it is necessary to distinguish between the space average (at a given instant) and the time average (at a given point).
Sound energy density level
The sound energy density level gives the ratio of a sound incidence as a sound energy value in comparison to the reference level of 1 pPa (= 10
−12 pascals). It is a logarithmic measure of the ratio of two sound energy densities. The unit of the sound energy density level is the
decibel (dB), a non-SI unit accepted for use with the SI Units.
[ Bureau international des poids et mesures]
''Le Système international d’unités (SI) / The International System of Units (SI)'', 9th ed.
(Sèvres: 2019), ISBN 978‑92‑822‑2272‑0, c. 4, Table 8.
The sound energy density level, ''L''(''E''), for a given sound energy density, ''E''
1, in pascals, is
:
,
where ''E''
0 is the standard reference sound energy density
Deutsches Institut für Normung
' (DIN; in English, the German Institute for Standardisation Registered Association) is the German national organization for standardization and is the German ISO member body. DIN is a German Registered Association ('' e.V.'') headquartere ...
, ''Akustik—Begriffe, Acoustics—Terminology'', Norm, Standard, â„
DIN 1320:2009-12
(Berlin: Beuth, 2009‑12).
:
 .
See also
*
Particle velocity level
*
Sound intensity level
Sound intensity, also known as acoustic intensity, is defined as the power carried by sound waves per unit area in a direction perpendicular to that area. The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m2 ...
References
External links
Conversion: sound intensity to sound intensity levelRelationships of acoustic quantities associated with a plane progressive acoustic sound wave - pdf
Acoustics
Sound
Sound measurements
Physical quantities