Larson Davis System 824, Technical Reference Manual

Page: 400 / 673

11-34 824 Reference Manual 9/29/09
Highlight “RT-60” and press the
c
check key.
RT60
The RT-60 analysis display uses the ByTime history to
calculate a room decay time. This time is calculated from the
cursor position to a point a number of dB down as set by the
“RT60 dB Down” setting and then extrapolated to a drop of
60 dB using a “Least Squares” slope calculation method.
The
u
up and
d
down arrow
keys move you to the next higher and
lower filter frequency. The
l
left
and
r
right arrow keys move you
to the previous and next ByTime
sample.
An auto-select routine will automatically locate the cursor to
be 5 dB below the maximum level. The auto-select is
executed on demand from the check menu and the first time
the RT-60 display is selected. There is a vertical line for the
cursor specifying the beginning of the measurement and a
horizontal line drawn at the dB down level.
If auto RT60 is set to “Yes”, the
auto-select routine will be performed
whenever a new filter is selected. Auto-select also sets the horizontal zoom so that the whole
decay fits on screen.
RT-60 time in seconds at frequency shown
Display label
RT-60 dB down setting
RT-60 delta time
Horizontal graph scaling
Selected filter frequency
ByTime sample time
Total number of ByTime samples
Current ByTime sample number