Larson Davis 831, User Manual

Page: 286 / 548

Model 831 Manual Manually Controlling the Internal Noise Source 15-19
If the trigger source is set to Z or
Mid Band, a cursor will not be
shown.
FIGURE 15-27 Linked Controls
Hints on Making a Good RT-60 Measurement
• Make sure the exit time is long enough to allow egress
and any residual noise to die down
• Turn off your cell phone and remove other possible
sources of sound contamination.
• Be quiet during the background level measurement
(between the exit period and filling the pre-trigger buffer.
See the “Measurement State Sequence” on page 15-5’.
• Minimize the ambient noise in the room by turning off
the mechanical equipment (i.e., HVAC units).
• Close doors, windows, and partitions to reduce
reverberant energy from adjoining areas.
• Use a sound source with repeatable amplitude and
spectral content.
• Use the exclude feature when something goes wrong. It
is a good idea to configure the instrument to take a few
more decays than what is required just in case.
• Trigger near the maximum level. For interrupted noise
method measurements, a few trial runs may be required
to determine a good trigger point due to the requirement
that the noise source level be above the trigger level for a
specific duration (Build Time).