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ISO 80000-8

ISO 80000-8:2007 is an ISO standard entitled Quantities and units – Part 8: Acoustics, which supersedes ISO 31-7.[1] It is a part of the group of standards called ISO/IEC 80000. The standard specifies names, symbols for quantities and units of acoustics and provides definitions for these quantities and units.

Contents list

The standard is divided into the following chapters:

  • Foreword
  • Introduction
  1. Scope
  2. Normative references
  3. Names, symbols and definitions


The standard includes definitions of sound pressure, sound power and sound exposure, and their corresponding levels: sound pressure level, sound power level and sound exposure level. For example

  • period duration (symbol T): duration of one cycle of a periodic phenomenon
  • frequency (symbol f): f = 1/T
  • logarithmic frequency interval (symbol G): G = lb(f2/f1)
  • angular frequency (symbol ω): ω = 2πf
  • wavelength (symbol λ): for a sinusoidal wave and in a direction perpendicular to the wavefront, distance between two successive points where at a given instant the phase ... differs by 2 π
  • wavenumber (symbol σ): σ = 1/λ
  • angular wavenumber (symbol k): k = ω/c
  • density (symbol ρ): ρ = m/V
  • static pressure (symbol ps): pressure that would exist in the absence of sound waves
  • sound pressure (symbol p): difference between instantaneous total pressure and static pressure
  • sound particle displacement (symbol δ): instantaneous displacement of a particle in a medium from what would be its position in the absence of sound waves
  • sound particle velocity (symbol v,u): v = dδ/dt
  • sound particle acceleration (symbol a): a = dv/dt
  • sound volume velocity (symbol q): surface integral of the normal component of the sound particle velocity ... over the cross-section (through which the sound propagates)
  • phase speed of sound (symbol c): c = ω/k
  • group speed of sound (symbol cg): cg = dω/dk
  • sound energy density (symbol w): time-averaged sound energy in a given volume divided by that volume
  • sound power (symbol P, Pa): through a surface, product of the sound pressure ... and the component of the particle velocity ... at a point on the surface in the direction normal to the surface, integrated over that surface
  • sound intensity (symbol i): i = p.v
  • time-averaged sound intensity (symbol I):
  • sound exposure (symbol E):
  • characteristic impedance of a medium (symbol Zc): at a point in a non-dissipative medium and for a plane progressive wave, the quotient of the sound pressure ... by the component of the sound particle velocity ... in the direction of the wave propagation
  • acoustic impedance (symbol Za): at a surface, the complex quotient of the average sound pressure ... over that surface by the sound volume flow rate ... through that surface
  • mechanical surface impedance (symbol Zm): at a surface, the complex quotient of the total force on the surface by the component of the average sound particle velocity ... at the surface in the direction of the force
  • sound pressure level (symbol Lp):
  • sound power level (symbol LW):
  • sound exposure level (symbol LE):
  • attenuation coefficient (symbol α):
  • phase coefficient (symbol β):
  • propagation coefficient (symbol γ):
  • dissipation factor for sound power (symbol δ, ψ):
  • reflection factor for sound power (symbol r):
  • transmission factor for sound power (symbol τ):
  • absorption factor for sound power (symbol α):
  • sound reduction index (symbol R):
  • equivalent absorption area of a surface or object (symbol A):
  • reverberation time (symbol Tn):

See also


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