V : Sound and Vibration Terms and Definitions ...
have both magnitude and direction, for example
are vector quantities. As opposed to
which have magnitude but no direction.
Vectors can only be added, subtracted or multiplied using mathematical procedures that take account of the co-ordinates.
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.
the rate of change of position, a vector quantity
as both speed and direction are required to define it, the SI units are m/s (metres per second).
v = u + at where v = velocity, u = start velocity, a = acceleration in m/s2
and t = time.
In the field of vibration
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.
Velocity of Sound
is usually taken to mean the speed of sound
. Not be confused with sound particle velocity
, which is the velocity of the individual particles of the medium
the sound wave is passing through. To add to the confusion the unit v is often included.
Velocity Level (Lv)
also known as vibratory velocity level
= 20 lg(v/vo
) dB re 1 nm/s
Velocity reference level : vo = 1 nm/s ≡ 0 dB (defined in ISO 1683) *
An increase or decrease in velocity of 20 dB = a factor of 10
40 dB = a factor of 100
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'
angular velocity. •
particle velocity, used in acoustic wave theory •
peak particle velocity •
standard reference levels table •
and the IEC definition of level
is the movement of particles
in an elastic medium
about an equilibrium
position. The movement may be periodic such as the motion of a pendulum or random.
Vibration is commonly expressed in terms of
frequency which are related.
Vibration Acceleration Level
Vibration at Work Regulations
, came into force in July 2005 to protect workers from risks to their health from vibration, based on
whole body vibration exposure action and limiting values
Vibration Dose Value
Vibration Exposure Action Value
Vibration Exposure Limit Value
Vibration Reference Levels
Vibration Weighting Networks
Vibration White Finger
Vibratory Acceleration Level
Vibratory Velocity Level
Viscous Damping Definition (IEC 801-24-22) 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
See also other damping topics.
, 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)
is the voltage expressed in decibels
, relative to 1 volt rms
, regardless of impedance.
LV = 20 lg (V/Vo) dBV, the reference voltage
: Vo = 1 volt ≡ 0 dB
a scalar quantity
, is the amount of space that an object or substance occupies, the SI unit is the metre-cubed (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 flow rate is also known as the volume flow rate, rate of fluid flow and volume velocity.
Volumetric Flux (q), the volumetric flow rate across a unit area. SI units : m3·s-1·m-2
Volumetric Power Density, volume based power density - watt/m3
VWF : Vibration White Finger
Certified Sound and Vibration Instrumentation for Hire.