# 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

## Examples

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):