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Sound Energy : Definitions, Terms, Units and Measurements
Sound Energy causes mechanical vibration in any medium through which a Sound Wave passes, including air and the human eardrum. The SI units of Sound Energy are joules = watt seconds.
Energy : J : = Force x Distance = Work, a quantity equivalent to the capacity of a physical system to do work; the SI unit of energy is the same as the unit of work - the Joule J and is a Scalar quantity.
1 J = 1 N·m = 1 kg·m
2/s 2 = 1 W·s = 10 7 ergs
Energy Flux Density : sometimes known as Intensity
Energy Spectral Density : ESD : describes how the energy of a signal or a time series is distributed with frequency.
Sound Energy : W : is the energy present in a sound field. W = Wo · 10
L J .... the units are Joules = Watt seconds W/10
Sound Energy Level : Lw = 10 lg W/Wo dB re 1 pJ or 10 -12 Joule.
Sound Energy Density sum of IEC Definition: Instantaneous Potential and Kinetic Energy Densities
Sound Energy Density : E : is the
Time-Averaged Sound Energy per unit volume, the units are J/m 3 or W·s/m 3
E = I/c : where I is
Sound Intensity in W/m 2 and c is the Speed of Sound in m/s.
E also equals Sound Particle Velocity squared x
Once again because of the wide range of the human ear the absolute values of
Sound Energy Densities are enormous. The decibel ratio to a threshold level produces manageable values - hence the
Sound Energy Density Level : L = 10 lg (E/E E o) dB re 10 -12 J/m 3 or W·s/m 3 Standard Reference Sound Energy Density Level
= 1 x 10
0 dB = 1 x 10
20 dB = 1 x 10
40 dB = 1 x 10
20 dB is a factor of 100
40 dB is a factor of 10000
Instantaneous Kinetic Sound Energy Density : half the product of the IEC Definition Density of the medium and the square of the Particle Velocity in the said medium.
Total Sound Energy Density : sum of IEC Definition Instantaneous Potential and Kinetic Energy Densities.
Sound Energy Flux the time average product of the in-phase components of the
IEC Definition Instantaneous Sound Pressure and the
Volume Velocity through the surface element considered. Also known as sound power through a surface element.
Sound Energy Flux : q : SI units : W/m 2 = J s/m 2
Sound Energy Flux Density : is the Sound Energy Flux in a specified direction and sense through an area perpendicular to that direction, divided by the area.
Sound Energy Flux Density Level : is the logarithm of the ratio of a given Sound Intensity in a stated direction to the reference sound intensity.
Specific Energy : is the energy per unit mass : joule per kilogram - J/kg
See also :
Related Terms :
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