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

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

### 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/s^{2} 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/s^{2} = 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

**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 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.

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

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**Vibration Parameters** :

Acceleration

Velocity

Displacement

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

**Vibration Regulations : ** see Vibration at Work Regulations above

**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 : m^{3}

**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 m^{3}/s.

**Volumetric Flux : q** : is the Volumetric Flow Rate across a unit area.

SI units m^{3}·s^{-1}·m^{-2}

**Volumetric Power Density** : volume based Power Density - watt/m^{3}

**Volume Velocity** : is the Sound Pressure divided by the Acoustic Impedance and is defined as integral, over a vibration surface, of the product of the component of Particle Velocity normal to the surface and the differential surface area.