Iso-Tech SLM 52N - Page 24

EN-22
The time weighting network of the sound level meter performs index averaging on the
square of the sound pressure signal. The equivalent circuit is shown at right. τ
ττ
τ is the
time constant, which equals CR.
The response of the index averaging circuit to a single burst signal is shown below.
C
R
：Input voltage
= C R
：Output voltage
Equivalent electrical circuit
e i
e i
e o
e o
e
i :
Input voltage (proportional to
square of sound pressure)
e
o
: Output voltage
e : Logarithm base
τ
ττ
τ : Time constant
t : Time
e i
e
e i
1
( 1- )
t
t
Signal amplitude
rms amplitude
e
o
Burst signal response