CASELLA CEL CEL-490 Instrukcja Użytkownika Pobierz pdf (Strona 68)

CEL-63x Environmental Noise Meter

68 Casella CEL

Fast time

weighting

A standard time weighting applied to measurements.

Most measurements are made using the Fast time

weighting. When using this setting, the instrument

applies a ⅛-second (125 ms) time constant when

calculating the sound pressure level.

Fast measurements are identified by using the subscript

„F‟.

Impulsive time

weighting

A standard time weighting applied to measurements.

When using this setting, the instrument applies a 35 ms

time constant to rising signals and a 1500 ms time

constant to decaying signals when calculating a sound

pressure level.

The Impulse Time Constant was traditionally used to

display an impulsive type noise, allowing the maximum

levels to be more easily seen on a changing display.

Impulsive measurements are identified by using the

subscript „I‟.

A-weighted

exposure level

The level that would contain the same amount of energy

in one second as the actual noise has during the whole

measurement period.

Aeq

A-weighted

equivalent

continuous sound

energy level

(also L

Ceq

, L

Zeq

)

The A-weighted (also C-weighted, Z-weighted) steady

level that would contain the same amount of noise energy

as in the actual noise, effectively giving an average level

over the measurement period.

Following the ISO procedures, doubling the energy results

in a 3 dB change in the L

. This is denoted by the

exchange rate Q=3.

Example

If the noise level in a factory were a constant 85 dB and

the measurement period were 4 hours, the L

Aeq

would be

85 dB(A).

The calculation of L

Aeq

does not use a threshold as in the

calculation of L

Avg

, except for the L

Aeq

(T80) function

defined for the ACGIH standard.

(also L

and L

)

The A-weighted sound pressure level measured using fast

time weighting (also with Slow and Impulse time

weighting).

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