Acoustic Glossary
Noise and Vibration Terms and Parameters
V
VDV : Vibration Dose Value .
Vector : a quantity having both magnitude and direction, especially as determining the position of one point in space relative to another. A vector is defined as an element of a vector space. Vectors can be added, subtracted or multiplied using mathematical procedures that take account of the co-ordinates.
Vector space : vector spaces are applied throughout mathematics, science and engineering. They are the linear-algebraic notion to deal with systems of linear equations; offer a framework for Fourier expansion or provide an environment that can be used for solution techniques for partial differential equations.
Velocity : v : the rate of change of position and is a vector quantity as both speed and direction are required to define it. The SI units are metres per second: (m/s).
v = u + at where v = velocity, u = start velocity, a = acceleration in m/s2 and t = time.
In the field of vibration acceleration a, velocity v, displacement s and angular frequency ω are related. - for example v = a/ω, s = v/ω, where ω = 2·π·f
It follows that 10 m/s2 = 0.01 m/s = 10 µm at 159 Hz
This works for all frequencies, we just chose 159 Hz to keep the numbers simple. We also have a vibration nomogram for downloading.
See also sound particle velocity.
Vibration : mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random.
Vibration is commonly expressed in terms of acceleration, velocity, displacement and frequency which are related.
See also the table of decibel reference levels.
Vibration at Work Regulations : The Control of Vibration at Work Regulations 2005 (the Vibration Regulations), came into force on 6 July 2005 and aim to protect workers from risks to health from vibration. The regulations introduce action and limit values for hand arm and whole body vibration.
see also the acceleration equivalent value : Aeq and hand arm vibration syndrome : HAVS
Vibration Dose Value : VDV : cumulative measurement of the vibration level received over an 8-hour or 16-hour period. It is the integrated fourth power vibration value with units m/s1.75 and has the advantage of sensitivity to vibration peak levels.
The eVDV - Estimated Vibration Dose Values use an alternative formulae which enables the VDV to be estimated from early on in the measurement.
BS 6472 provides guidance for VDV levels in residential buildings
See also whole body vibration and see the Vibration at Work Regulations.
Vibration Parameters : The main vibration parameters are Acceleration, Velocity, Displacement. Click a link to see details and sub-parameters if that's a good word
Vibration Reference Levels
Vibration Reference Level - acceleration = 10 micro-m/s2 (10 µm/s2)
Vibration Reference Level - velocity = 1 x 10-8 m/s
Vibration Velocity Level : Lv : = 20 log(v/vo) dB re 10-8 m/s = 10-6 cm/s
* Velocity Reference Level = 1 x 10-8 m/s
an increase or decrease in velocity of 20 dB = a factor of 10
a 40 dB = a factor of 100
a 60 dB = a factor of 1000 ... etc.,
See also the table of other Standard Reference Levels
Vibration Weighting Networks
Vibration White Finger : VWF : see also Hand Arm Vibration Syndrome.
Voltage Level : LV : dB(1 VRMS) : voltage relative to 1 volt, regardless of impedance.
Lv = 20 log (V/Vo) dBV
Reference voltage Vo = 1 volt = 0 dB
Volume : V : the SI unit is the cubic metre : m3
Volumetric Flow : also known as volume flow rate or rate of fluid flow is the volume of fluid which passes through a given surface per unit time, the units are - m3/s
Volumetric Power Density : volume based power density - watt/m3
VWF : Vibration White Finger : Hand Arm Vibration Syndrome.
Other Glossary Terms
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