Table 8A Objectives and Key Acoustic Results of Model Studies

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Table 8A Objectives and Key Acoustic Results of Model Studies -Cont.

Table 8A

Objectives and Key Acoustic Results of Model Studies

Miramar Model Study (October 1975) [3]

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ACOUSTIC

OBJECTIVES

RESULTS

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1. Verify acoustical performance of a

1. Exhaust noise of an F-14 in

full-scale hush-house for F-14

maximum afterburner was

aircraft.

predicted to meet the 85 dBA

criteria at 250 ft.

2. Provide design information for

future hush-house and test cell

2. a) A method was developed

designs.

to predict a jet sound power

spectrum based on jet total

temperature nozzle pressure

ratio, and nozzle diameter.

b) The division of

acoustic energy between the

interior and exterior of the

hush-house depends strongly

on the axial distance between

the jet and the augmenter

entrance. Increasing this

distance resulted in more

energy in the interior, and

less energy entering the

augmenter.

c) Augmenter attenuation

as a function of axial posi-

tion of the acoustic lining

in the augmenter was found to

be approximately independent

of position, except that

little attenuation occurred

at low frequencies in the

upstream end of the augmenter

(at least partly because low

frequencies are generated

farther downstream in the

jet) and little attenuation

occured at high frequencies

in the downstream end of the

augmenter.