Gracey & Associates
Noise and Vibration
Glossary - W
GLOSSARY INDEX:
A B C
D E F
G H I
J K L
M N O
P Q R
S T U
V W X
Y Z
W : see Watt.
Waterfall : a 3-D plot displaying the amplitude of spectral components as a function of both time and frequency. The frequency spectrum is displayed as a curve for each specified time instant. Several such curves, for different time instants, are displayed simultaneously.
Watt : W : the unit of power.
The rate at which work is done, or (equivalently) the rate at which energy is expended. One watt is the power which in one second gives rise to energy of 1 joule.
1 watt = 1 J/s = 1 N·m/s : base unit m2 kg s-3
Watt per square meter : W/m2 : a common metric unit of heat, flux, density, irradiance.
base unit: kg s-3
Watt second : W·s : a common metric unit of work or energy, representing the energy delivered at a rate of one watt for a period of one second.
1 watt second = 1 J = 1 N·m
Waveform : the waveform is the shape of a time domain signal as seen on an oscilloscope screen. It is a visual representation or graph of the instantaneous value of the signal plotted against time. Inspection of the waveform can sometimes reveal information about the signal that the spectrum of the signal does not show. For instance a sharp spike or impulse and a randomly varying continuous signal can have spectra that look almost identical, while their waveforms are completely different. In machine vibration, spikes are usually caused by mechanical impacting, while random noise can be caused by the advanced stages of bearing degradation
Wavelength : Λ : for a sound wave is 345 m/s (speed of sound) divided by the frequency - the unit is metres. Wavelength is also defined as the distance between repeating units of a sound wave. 20 Hz = 17 m and 20 kHz = 17 mm.
The frequency f, wavelength λ and wave velocity v are related by the formulae λ = v/f
Weber : Wb : is the SI unit of magnetic flux, volt-seconds, causing the the electromotive force of one volt in a circuit of one turn when generated or removed in 1 second.
Weekly Personal Noise Exposure Level : LEP,w : a measure of the total noise received by an employee during a working week. It is similar to the daily noise exposure but is calculated for a 40-hour week (five 8-hour days) instead of an 8-hour day. See also sound exposure level.
Weighted Sound Reduction Index : RW : a single-number quantity which characterises the airborne sound insulation of a material or building element over a range of frequencies - laboratory measurement.
Weighted Standardized Impact Sound Pressure Level : LnT,w : single number quantity used to characterize the impact sound insulation of floors, based on laboratory measurement of LnT.
Weighted Standardized Impact Sound Pressure Level : L'nT,w : single number quantity used to characterize the impact sound insulation of floors, based on field measurement of L'nT.
Building Regulations : Approved Document E - preferred parameter.
Weighted Standardized Level Difference : DnT,w : for airborne sound transmission. A single number quantity which characterises the airborne sound insulation between rooms, calculated from the DnT.
Building Regulations : Approved Document E - preferred parameter.
Weighting Curve : see Weighting Network.
Weighting Filter : see Weighting Network.
Weighting Network : an electronic filter in a sound level meter or a vibration meter that correlates the objective meter measurement to the human response. For example the frequency response of the human ear, in which case the A-weighting network is most commonly used. Similarly a hand-arm system has a frequency-dependent sensitivity, so measurement of the vibration signal must follow the same shape. There are a range of human vibration networks or filters because measurements are made in 3-axis and the weightings for whole-body measurements, seated, standing or lying down are different from the hand-arm filters see the list below.
Weighting Network Bb : for measuring whole-body vibration in fixed-guide transport systems in seated or recumbent positions.
Weighting Network Bc : for measuring horizontal whole-body vibration in the X direction, perpendicular to the spinal column, at the seat back.
Weighting Network Bd : for measuring horizontal whole-body vibration in the X and Y directions, at right angles to the spinal column, in seated, standing or recumbent positions.
Weighting Network Be : for measuring rotational whole-body vibration in 3-axis.
Weighting Network Bg : for evaluation of whole-body vibration in the Z direction, with regard to hand control and visibility.
Weighting Network Bh : for measuring hand-arm vibration in the X / Y / Z axis.
Weighting Network Bj : for measuring vibration acting on the head of a recumbent person in the vertical direction, perpendicular to the lying surface.
Weighting Network Bk : for measuring whole-body vibrations in the direction of the spinal column in seated and standing positions, for measurements in the vertical direction, perpendicular to the lying surface in recumbent position and for measurements in the X / Y / Z axis acting on the feet in seated position.
Weighting Network Bm : for measuring whole-body vibrations in buildings in the X / Y / Z axis.
Weighting Window : Fast Fourier Transform theory tells us that time and frequency are simply two alternative ways of observing a signal. By changing the nature of a signal in the time domain, we implicitly change the nature of the spectrum in the frequency domain. This is exactly what we do when we apply a weighting function or time window.
White Finger : disorder of the hands caused by using hand-held tools, such as chain saws and jackhammers. Results in reduction of the hand's ability to feel or to regulate its temperature. May also result in numbness and excessive sensitivity to low temperatures. Called Raynaud's disease.
White Noise : sound containing all audible frequencies with equal intensity - see also pink noise.
Whole Body Vibration Syndrome : our bodies are exposed to vibration at work from many machines, such as construction machinery (bulldozers, tow motors, forklifts and cranes), heavy equipment (grinders, jack hammers), and power hand tools. Vibration has been proven to result in disorders of both the hand and arm, the neck, and the back. See also The Control of Vibration at Work Regulations and Vibration Dose Value - VDV .
Whole Body Weightings
Widedband Noise : also called broadband noise - noise whose energy is distributed over a wide section of the audible range as opposed to narrow band noise.
Windowing : a technique used to reduce spectral leakage by multiplying the time-domain waveform by a window function. The process of windowing reduces the amplitudes of discontinuities at the edges of a waveform, thereby reducing spectral leakage.
Work : = force x distance = energy and is defined as the amount of energy transferred by a force. Like energy it is a scalar quantity with SI unit of both work and energy is the joule.
WVBS : Whole Body Vibration Syndrome. .
GLOSSARY INDEX:
A B C
D E F
G H I
J K L
M N O
P Q R
S T U
V W X
Y Z
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