Far field noise data were taken for convergent nozzles of various shapes and sizes at subsonic velocities exceeding 400 feet per second. For a circular nozzle, the nozzle inlet shape and lip thickness had no effect on the noise level, directivity, or spectra when compared at the same nozzle exit diameter and peak exhaust velocity. A sharp edged orifice was one exception to this statement. Coannular nozzles can produce additional high frequency noise. Blunt ended centerbodies, where there is significant base drag, also generate significant additional noise.The total noise power generation was essentially the same for cirpular, slot, and plug nozzles of good aerodynamic shape. The noise radiation patterns were essentially the same for these nozzle shapes except°° near the nozzle exhaust axis. These patterns were well described by "7 '(1 -M C cos 9j)~3, except near the nozzle exhaust axis. w

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R e s u l t s f r o n experimental work on c o d e l s c a l e cascade r e v e r s e r s w i t h cold a i r f l o w a r e presented.Sound power l e v e l d i r e c t i v F t y and s p e c t r a l c h a r a c t e r i s t 5 c s f o r cascade r e v e r s e r s a r e r e 2 o r t e d . E f f e c t of cascade e x i t a r e a r a t i o , vane p r o f i l e shape, a26 emission a r c a r e discussed.Model equivalent diameters v a r i e d from 3 t o 5 i n c h e s ; p r e s s u r e r a t i o s ranged from 1.15 t o 3.0.Depending on t h e r e v e r s e r type, a c o u s t i c power was ~r o p o r t i o n a l t o t h e 4 1 t o 6 t h potrer of i d e z l jet v e l o c i t y . Reverser 2 n o i s e peaked a t h i g h e r frequency and vas more c x n i d i r e c t i o n a l than nozzlea l o n e j e t noise. A~p s e c i a b l e reduction i n s i d e l i n e n o i s e x a s obtained from plan€ s h i e l d s . Airfoil-vaned casczdes were t h e most aerodynamically e f f i c i e n t and l e a s t n o i s y r e v e r s e r s . Scaling of cascade r e v e r s e r d a t a t o e x m p l e a i r c r a f t engLnes showed 211 cascades above t h e 95 PXdB s i d e l i n eg o a l f o r STOL a i r c r a f t o Hovever, t h e a i r f o i l -~r a n e i r e v e r s e r h a s a good p o t e n t i a l f o r meeting t h i s goal f o r high Sypass (low p r e s s u r e r a t i o ) exhavsts . I n t r o d u c t i o nOne of t h e a i r c r a f t n o i s e sources t h a t can becone i n p o r t a n t i n m e e ting community n o i s e r e g u l a t i o n s , e s ? e c i a l l y f o r srnall a i r p o r t s i n h e a v i l y populated z r e a s , i s t h e t h r u s t r e v e r s e r used t o reduce ground r o l l . There have been numerous s t u d i e s of t h e aerodynamic l;erfornazlce of small s i z e t h m s t r e v e r s e r s ( e . g . , r e f . 1); hovever, s t u d i e s of r e v e r s e r n o i s e have n o t been a v a i l a b l e i n t h e l i t e r a t u r e . For t k i s reason, t h e NASALewis Research Center has been conducting an i n v e s t i g a t i o n of t h e n o i s e c h a r a c t e r i s t i c s of v a r i o u s types of r e v e r s e r s , i n c l u d i n g target-type r e v e r s e r s f o r c i r c u l a r and s l o t n o z z l e s , an5 cascade r e v e r s e r s with and -.without s h i e l d i n g . Thls information, t o g e t h e r w i~h c o s t , a e r o d y n m i c e f f i c i e n c y and mechanical f e a s i b i l i t y c o n s i d e r a t i o n s , should b e of v a l u e i n t h e design of r e v e r s e r s f o r a tiide range of engine a p p l i c a t i o n s . R e s u l t s of t a r g e t -t y p e r e v e r s e r n o i s e studFes have been presented i n r e f e r e n c e s 2 t o 5. A c o r r e l a t i o n of soae of t h e d a t e f r o n r e f e r e n c e 2 i s presented i n r e f e r e n c e 6. Preliminary r e s u l t s f o r cascade r e v e r s e r n o i s e are now 2vaFlable f r o n c o l d f l o v model t e s t s of cascade c o n f i g u r a t i o n s wrth a i r f o i l shaped vanes and constant-thickness vane...

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