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

**VDV** : Vibration Dose Value

**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 **Vibratory Velocity Level : Lv** = 20 lg(v/vo) dB re 1 nm/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.

* ISO 1683 also states : 'in connection with structure-borne sound, a reference value of 50 nm/s is also in use. In this event, the vibratory velocity level takes values close to the associated sound pressure and sound intensity levels'

See also :
Angular Velocity. •
Particle Velocity, used in acoustic wave theory •
Peak Particle Velocity •
Standard Reference Levels table •
Volume Velocity
and the **IEC Definition** of Level

**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.

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.

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**

Acceleration

Velocity

Displacement

Vibration Reference Levels

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

Vibration Velocity Level : Lv

Vibration Weighting Networks

Vibration White Finger : VWF

Vibratory Acceleration Level

### damping that occurs when a particle in an oscillating system is resisted by a force that has a magnitude proportional to the magnitude of the velocity of the particle and direction opposite to the direction of the particle

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

The 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}

### 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