SV SLA-PA201, Руководство пользователя

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gradually in the high frequency region. But the integrated values(velocity or displacement) have a
very small values less than -50dB. Finally, the errors rarely affect the integrated value.
The integrated values have linearity in the low frequency which is in range of 23% of sampling
frequency. If a sampling frequency is set 10 times of the wanted frequency, we can get a good
linearity in the wanted frequency. Therefore, the sampling frequency is set 1024Hz because the useful
frequency range in the human vibration level meter is 80Hz.
[Fig. IV-1-9] Frequency Response [Fig. IV-1-10] Phase Response
1. 5
Sound Pressure Level Calculation
Differently with Vibration Level Meter, you can calculate dB value of measured sound signal
which uses microphone using such below basic theory through the chapter1.1 to 1.4.
Sound Pressure Level (SPL) is composed as below.
10
( ) 20 log
rms
P
ref
p
SPL L
p
⎛ ⎞
′
= ⋅
⎜ ⎟
⎜ ⎟
⎝ ⎠
rms
p
′
: Root Mean Square (Pa)
ref
p
: Reference Sound Level (20
Pa
μ
)
Equivalent continuous Sound Pressure Level (
eq
L
) is expressed as below.
2
10
1
10 log
eq
ref
p
L
T p
⎛ ⎞
⎛ ⎞
′
⎜ ⎟
= ⋅
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎝ ⎠
⎝ ⎠
∑
p
′
: Real Sound Pressure (Pa)
ref
p
: Reference Sound Level (20
Pa
μ
)
T
: Measurement Time
You can get Equivalent continuous A-weighted sound pressure level when A-weighted
A
p
′
replaces
p
′
from this equation.