The design
of
the Reverberation Processor
is
based
on the
"Method
of
Integrated Tone Burst"
suggested
by
M.R. Schroeder and modified
by
H.
Kuttruff.
The
use
of
this method results in very smooth decay curves, giving
a very accurate determination
of
the initial slope
of
the curve. The
"Early
Decay
Time"
(the reverberation
time
extrapolated
from
the upper
part
if
the decay curve)
can
be
directly
read
from
the meter
of
Type
4422.
A set-up
for
measuring reverberation times
is
shown in Fig.5.3.
Type 2796
is
used
to
amplify the
output
signal
from
the Band
Pass
Filter
Set Type 1615.
When
calibrating the excitation pulse, the
ATTENUATOR
and
the GAIN CONTROL
of
the Power
Amplifier
are
set
so
that
the
output
signal level
is
just below the clipping
limit.
Reverberation
curves
measured
using the set-up
are
shown in Fig.5.4.
For more details on the
"Method
of
Integrated Tone
Burst"
and
on the
Reverberation Processor, reference should
be
made
to
the instruction
manual
for
Type 4422.
aoooao
oo
ooo
o
oooooo
ooo
oooooooo
o
ooooooooa
oaoooaoo
o
ooao
oa
o
.....
...
~
Church
in Nrerum
~
Tota
l
Range
25
dB
E=:
soo
Hz, .1/3 oct.
!==
SIN - 50 dB
~
Potent
i
omet
er
Rang
e
50
dB
~
Writing
Speed
500 mm/s
GP
1102
Schroeder/
Kut
tru
ff
's
Method
5 dB
Fig.
5.4. Reverberation Decay Curves, repetitive recordings
5.4. GENERAL
USE
IN ACOUSTICS
171417
The Power
Amplifier
Type 2706
will
be
found very useful in acoustics
measurements
to
supply a loudspeaker at a suitable level
for
reverberation,
sound insulation, microphone
and
loudspeaker measurements.
17
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