NTi Audio Acoustilyzer AL1 - Manual (Page 38)

b. How to measure
The room under test is injected with a pink noise signal through speakers.
The sound source has to be active until a balance between injected and
absorbed acoustical energy has been reached. i.e. allow enough time for
the sound to reflect off all surfaces. As a rule of thumb, the noise should
be played for at least the number of seconds recorded in the RT60 result.
The source signal is then stopped. The AL1 recognizes this interruption,
triggers, the decay time is measured and the RT60 test result is automatically
calculated.
Please follow the RT60 test instruction below:
Ranging
• Select RANGE and press the enter key
to measure the actual sound pressure
level in the room without a test signal
present.
• The SET RANGE field pops up. Confirm
the automatic ranging with OK.
Now the RT60 upper mark indicators are
set to the minimum pink noise level needed
to successfully complete a measurement.
The lower marks indicate the environmental
noise without any test signal present.
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