SP395 SoundPro Audio Integrator
Form7492
Operation Manual
45
6.
Decay Range –
This field shows the dB difference between the Max Noise and Min
Room levels, minus 6 dB to allow for 6 dB test headroom. The Reverb Decay test
measures the time taken for the sound energy to decrease by this amount. The display
automatically updates when the Min Room level has been set, and displays "--" if the
difference between the max and min levels is less than 20 dB. Adjust the sound system's
amplifier volume and/or the SP395 test generator output, or reduce the ambient
background noise to obtain a decay range greater than 20 dB. Larger dB decay ranges
produce better test results. If possible, try to attain a decay range of 35-45 dB.
7.
Speaker Distance (Value) –
Use this field to enter the approximate distance that the
SP395 microphone is from the nearest speaker. The reverb decay test uses this
information to ignore any possible early sounds that are not part of the normal test,
allowing the test to provide more accurate measurements with transient noise spikes. Turn
the control knob to highlight the Speaker Distance Value field. Click on the field and turn
the control knob to set the distance in 0.1 increments from 4 ft. to 999.9 ft. or the
equivalent range in meters. Click to select the desired value.
8.
Speaker Distance (Units)
– selects the unit of measurement used to set speaker distance
either feet (ft) or meters (m). To set the speaker distance units, turn the control knob to
highlight the Speaker Distance Units field, and click to select
m
(meters) or
ft
(feet).
9.
Test Interval –
This field sets the noise on-time duration (the off and on time are equal)
from 2 to 15 seconds in 1-second steps. This determines the longest RT60 time that can be
measured. Larger rooms require longer test intervals to allow the sound to build to
maximum and the sound to decay.
10.
RT60 Time –
This field shows the calculated RT60 reverberation time. The number is
extrapolated from the measured decay time by linearly extending the decay time and dB
decay range to a 60 dB drop in SPL.
11.
Generator Level –
This field allows you to make coarse adjustments of the pink noise
level. You may need to adjust the generator level to set Max Noise level for an acceptable
decay range. Highlight the field and click to select it (underlined). Turn the control knob
to the desired level then click to select the level setting.
Reverb Decay Time Operation
1.
Position the SP395 microphone in the center of the listening area
.
2.
Connect any SP395 line output
into an amplifier and speaker. Turn the level down at the
amplifier!
3.
Select the Reverb Decay Time function and select A-weighting.
A-weighting rolls off
most of the effects of low frequency room modes and provides a better indication of delay
time.
4.
Speaker Distance
.
Set the “Speaker” field to the approximate distance from the speaker
to the SP395’s microphone.
5.
Set the Test Interval.
Use short test times for small rooms, and longer test times for
larger rooms and rooms with minimal sound absorption. Choose a test interval long
enough to include the expected room reverberation time.
6.
Set Minimum Room Noise - Highlight the Test Control field and select "Set Min."
Allow the SP395 to read the average background noise level in the room. Click to capture
the minimum room level (ambient noise). If this level is greater than 50 dB, you should
attempt to decrease the ambient noise for best test results and better room acoustics.
7.
Set Maximum Room Level.
When you capture the minimum room noise (Set Min), the
display changes to "Set Max" and pink noise is applied to the amplifier input. Adjust the
amplifier's volume and/or the SP395 output level for a Max noise level of approximately
