Acoustic Glossary


V : Sound and Vibration Terms, Definitions, Units, Measurements ..

VDV : Vibration Dose Value

Vector : is a quantity having both magnitude and direction, for example Acceleration, Force and Velocity.

As opposed to Scalar Quantities like Density, Mass and Speed which have magnitude but no direction.

Vectors can only be added, subtracted or multiplied using mathematical procedures that take account of the co-ordinates. A vector is defined as an element of a vector space.

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 and Angular Frequency ω = 2·π·f , are related.

Velocity v = a/ω
Displacement s = v/ω

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 : Particle Velocity and Volume Velocity

Velocity Level : also known as Vibration Velocity Level : Lv : = 20 lg(v/vo) dB re 10-9 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.

Vibration Velocity Reference Level = 1 x 10-9 m/s

see also :

Angular Velocity.
Particle Velocity, used in acoustic wave theory
Peak Particle Velocity
Standard Reference Levels table
Volume Velocity

Velocity of Sound is usually taken to mean the Speed of Sound.

Should not be confused with Sound Particle Velocity, which is the velocity of the individual particles. To add to the confusion the unit v is often included.

Vibration : mechanical oscillations occur 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 dB Reference Levels and Vibration Dose

Vibration Acceleration Level : La

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 the Action and Limit Values for hand arm and whole body vibration.

For others details see the Government and/or HSE websites.

see also :

Acceleration Equivalent Value : Aeq
Hand Arm Vibration Syndrome : HAVS
Whole Body Vibration : WBV
Certified Vibration at Work Instrumentation

Vibration Dose Value : VDV

Vibration Parameters :

Click a link to more details and sub-parameters if that's a good word

Vibration Reference Levels

Vibration Regulations : see Vibration at Work Regulations above

Vibration Velocity Level : Lv

Vibration Weighting Networks

Vibration White Finger : VWF : under Hand Arm Vibration.

Voice Simulator : under Artificial Voice.

Volt : V : the derived SI Unit of electric potential; the potential difference between two points on a conductor carrying a current of 1 Ampere, when the Power dissipated between these points is 1 watt

Voltage Level : LV : dB (1 V rms) : voltage relative to 1 volt, regardless of impedance.

Lv = 20 lg (V/Vo) dBV

Reference voltage Vo = 1 volt = 0 dB

Volume : V : the amount of space that an object or substance occupies, the SI unit is the cubic metre : m3

Volumetric Flow Rate : Q : is the volume of fluid which passes through a given surface per unit time.

Q = v · A
where v = velocity, A = area/surface and the SI units are m3/s.

Volumetric Flux : q : is the Volumetric Flow Rate across a unit area.
SI units m3·s-1·m-2

Volumetric Power Density : volume based Power Density - watt/m3

Volume Velocity IEC Definition : integral, over a vibration surface, of the product of the component of Particle Velocity normal to the surface and the differential surface area

VWF : Vibration White Finger : under Hand Arm Vibration.


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