Quantcast Table 8C Objectives and Key Acoustic Results of Model Studies Forcing Cone Model Study

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Table 8C
Objectives and Key Acoustic Results of Model Studies
Forcing Cone Model Study (June 1983) [14, 17]
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OBJECTIVES
RESULTS
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1.  Compare acoustical
1. Attenuation was 3 to 6 dB
performance of a round cross
greater (avg. 4.6 dB) for the
section augmenter for the
F402 below 400 Hz full-scale.
TF-30 and F402 type engine.
Attenuation was 5 dB greater
for the TF-30 at 500 and 630
Hz 1/3 octave bands.
Attenuation was the same from
800 to 2000 Hz.
2.  Determine effect of a
2. Forcing cone produced no
"forcing cone" on performance
acoustical benefits; no change
of a round cross-section
in attenuation for the TF-30;
augmenter for the TF-30 and
slight degradation for the
F402 type engine.
F402.  Forcing cone not
recommended acoustical
purposes.
3.  Determine the effects
3. a) Filling the bottom half
of two modifications to a
of the airspace increased the
standard round augmenter with
attenuation by 2 to 5 dB
concentric shell and inner
between 80 and 160 Hz
lining:  a) completely fill
(full-scale)and decreased the
the lower half of the
attenuation 1 to 3 dB between
airspace with acoustical
25 and 63 Hz.
material; and b) insert thin
vertical acoustical "curtains"
b) Vertical curtain
into the airspace on both
increased the attenuation 1 to
sides of the inner lining.
4 dB between 0 and 60 Hz
and did not degrade low
frequency attenuation.
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