C-weighting

C and Ctr (spectrum adaption terms) - sound insulation

● Note 1 : such procedures are given in BS ISO 532-1:2017 methods for calculating loudness

See also equal loudness contours • loudness level

See also • hand arm vibration syndrome

CB (critical band)

CCLD (constant current line drive)

● Note : for a plane acoustic wave propagating in a non-dissipative medium, the specific acoustic impedance relative to this wave is equal to the

To take into account different cable lengths or to convert from charge sensitivity to voltage sensitivity, divide the *charge sensitivity* by the total capacitance of the accelerometer and the cable. For example a 1 pC/ms^{-2} and 9.8 pC/g accelerometer with a capacitance of 900 pF and a 1.2 m cable (100 pF), would give 1 pC / (900+100) pF = 1 mV/ms^{-2} or 9.8 pC / (900+100) pF = 9.8 mV/g. By definition 1 g = 9.807 ms^{-2} and conversely 10 ms^{-2} = 1.01 g

CIS (common intelligibility scale)

Clarity

**Class 1** precision grade sound level meters for laboratory and field use, also known as *Type 1*.

**Class 2** general grade sound level meters for field use, also known as *Type 2*.

● Note : octave and
one-third octave filters used for sound level measurements are also required to meet one of the above classes.

CNEL (community noise equivalent level)

**Coherent Output Power Spectrum ** a measure of what part of the (output) power spectrum is fully coherent with the input signal.

**Coherent Sources ** a sound arriving directly from a source and a sound arriving at the same point from the same source but modified by the reverberant field are said to be coherent. Changes in level, phase or time do not change the fact that the sound is coherent.

Coincidence Effect

Common Intelligibility Scale

See also the IEC Definition of Level

**Compliance**, conforming to environmental laws, regulations, standards and other requirements.

Compression Wave

● Note : conjugate impedances are expressed by conjugate complex quantities.

**Constant Percentage Bandwidth Filter** the 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 wider the bandwidth. The bandwidth is usually defined in octaves, 1/3 octaves or as a fixed percentage of the centre frequency of the filter.

See also fast fourier transform • line spectrum • narrowband noise • narrowband spectra • octave bands. pink noise • white noise • wideband noise

See also noise dose

**Correlation Coefficient** when the correlation is 1 then *perfect positive correlation* exists and -1 equates to a *perfect negative correlation*. 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.

1 picocoulomb = 1 x 10

See also uncoupled mode

CPB (constant percentage bandwidth filter)

Sound levels often have high **Crest Factors**, so hearing damage risk assessments require both the LAeq and the Peak values to be reported.

Criterion Level

Criterion Time

The notion of critical bands explains the auditory masking of a narrow band (sinusoidal) signal by a wideband noise source. Critical Band Frequencies.

See also loudness.

See also other acoustic damping topics

Critical Distance

Critical Frequency

See also autocorrelation

Ctr (spectrum adaption terms) - sound insulation

Cylindrical Wave

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