Gracey & Associates
Noise and Vibration
Glossary - C
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
C : Spectrum Adaption Term : these spectrum adaptation terms express how much the airborne sound insulation afforded by the wall or floor being tested would vary from the DnT,w figure if the noise source was A-weighted pink noise (C) or urban road traffic noise (Ctr)
C-weighting : a standard weighting of the audible frequencies, commonly used for the measurement of Peak Sound Pressure level. Approximately follows the 100 phon curve - also written as dB(C) or dBC.
Calibration : the process of measuring to determine the accuracy of your measurement chain. This result can then be used to offset measured values and take account of this inaccuracy.
Capacitor : an electrical component that passes alternating currents but blocks direct currents. Also called a condenser, it is capable of storing electrical energy
Carpal Tunnel Syndrome : see hand-arm vibration syndrome
CB : : Critical Band
CCLD : Constant Current Line Drive
CE Marking : a label to show that the Meter conforms to the specification of a European Directive.
Centre Frequency : the frequency in the middle of a band of frequencies, for example 1 kHz octave band.
Characteristic Impedance : Acoustic Impedance.
Charge Amplifier : An amplifier with low input impedance whose output voltage is proportional to the output charge from a piezoelectric transducer. Has the advantage that voltage output is not affected by length of connecting cable from the transducer.
Charge Injection Calibration : CIC : is a technique patented by Bruel & Kjaer for on-line verification of the integrity of the entire measurement chain, for example, microphone, preamplifier and cabling. .
Class 1 : precision grade meters for laboratory and field use - also known as Type 1.
Class 2 : general grade meters for field use - also known as Type 2.
Clipping : an electrical signal is clipped if the signal level exceeds the capabilities of the amplifier. It is a distortion of the signal.
CNEL : Community Noise Equivalent Level
Coherence : Coherence is a number between one and zero, and is a measure of the degree of linearity between two related signals, such as the excitation force (input) of a structure related to the vibration response to that force (output).
Coherent Output Power Spectrum : a measure of what part of the (output) power spectrum is fully coherent with the input signal.
Community Noise Equivalent Level : CNEL : the 24 hour average noise level of all hourly Leq measurements with a 10 dB penalty added to the levels between 2200 and 0700 hours and a 5 dB penalty added to the levels between 1900 and 2200 hours to reflect people's extra sensitivity to noise during the night and the evening.
Condenser : see Capacitor.
Constant Current Line Drive : CCLD : for IPC type accelerometers.
Constant Bandwidth Filter : a filter with fixed frequency bandwidth, expressed in Hertz (Hz), regardless of centre frequency.
Constant Percentage Bandwidth Filter : A filter whose bandwidth is a fixed percentage of centre frequency. The width of the individual filters is defined relative to their position in the range of interest. The higher the centre frequency of the filter, the higher the bandwidth. The bandwidth is defined in octaves or as a fixed percentage of the centre frequency of the filter.
Control of Noise at Work Regulations : The Control of Noise at Work Regulations 2005 (the Noise Regulations) came into force for all industry sectors in Great Britain on 6 April 2006 (except for the music and entertainment sectors where they came into force on 6 April 2008).
The aim of the Noise Regulations is to ensure that workers' hearing is protected from excessive noise at their place of work, which could cause them to lose their hearing and/or to suffer from tinnitus (permanent ringing in the ears).
The Control of Noise at Work Regulations 2005 replace the Noise at Work Regulations 1989.
see also sound exposure and noise dose
Control of 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 action and limit values for hand-arm and whole-body vibration.
see also the acceleration equivalent value : Aeq and hand-arm vibration syndrome : HAVS
Correlation : measures the degree to which two time domain signals. The higher the correlation, the stronger the relationship between both signals. See also autocorrelation and cross-correlation.
Correlation Coefficient : when the correlation is 1 or -1, a perfectly linear positive or negative relationship exists; when the correlation is 0, there is no relationship between the two sets of data.
Coulomb : C : a coulomb is a unit of electrical charge, defined as the quantity of electrical charge transferred by 1 ampere in 1 second. Symbol C. A Pico-coulomb is 1 x 10-12 coulombs
CPB Filter : Constant Bandwidth Filter
Crest Factor : the crest factor is peak amplitude of a waveform divided by the RMS value of the waveform. For example a sine wave has a crest factor of 1.414 or 3 dB. For a square wave the crest factor is 1.
Criterion Level : is the maximum Leq sound level allowed for an 8-hour period and corresponds to the 100% noise dose value.
Critical Band : The human ear combines sounds of similar frequency into frequency bands, called 'critical bands'. Zwicker divided the audio spectrum into 24 critical bands and named the units 'barks' - see also loudness . The notion of critical bands explains the auditory masking of a narrow band (sinusoidal) signal by a wideband noise source.
Cross Correlation : cross correlation is a measure of the similarity of two time domain signals. If the signals are identical, the cross correlation will be one, and if they are completely dissimilar, the cross correlation will be zero.
Cross Power Spectrum : measurement of two signals with an amplitude that is the product of the two signal amplitudes and a phase that is the difference of the two phases.
Cross Spectrum : the cross-spectrum is the forward Fourier transform of the cross-correlation function. Generally, the cross-spectrum is a complex function.
Cross-talk : the signal of one channel, track, or circuit interfering with another.
Ctr : the correction to a sound quantity such as the weighted standardized sound level difference DnT,w to take account of the specific sound spectrum.
cubic metre : m3 : volume.
cubic metre per kilogram : m3/kg : specific volume.
cubic metre per second : m3/s : volumetric flow.
Cumulative Distribution : a method of representing time-varying noise by indicating the percentage of time that the noise level is present above (or below) a series of amplitude levels.
Cursor : a thin hairline that can be positioned on a spectrum or time signal graphs to obtain a readout. Various types of cursor are available. For example, single cursor - a line, delta cursor - selects a band, harmonic cursor - marks a set of harmonics.
Cut-off Frequency : the frequencies that mark the ends of a band, or the points at which the characteristics of a filter change from pass to no-pass.
Cycle : the complete sequence of values of a periodic quantity that occurs during one period.
cycle per second : c/s : frequency.
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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