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Thermal relaxation in nitrogen with wet carbon dioxide as impurity
An e l e c t r o n b e a m a c o u s t i c i m a g e c o n v e r t e r operating in a pulsed t r a n s c e i v i n g mode D u b o i s , J . L. I E E E T r a n s a c t i o n s on s o n i c s a n d u l t r a s o n i c s , Vol S U - 1 6 , No 3 (July 1969) pp 9 4 - 1 0 2 An e l e c t r o n i c a l l y s c a n n e d a c o u s t i c i m a g e transceiver has been constructed that emp l o y s the a c o u s t i c i m a g e c o n v e r s i o n p r i n c i p l e p r o p o s e d by Sokoloff but t h a t o p e r a t e s in a p u l s e m o d e . T h i s a c o u s t i c i m a g i n g s y s t e m is u n i q u e a n d d i f f e r s f r o m p r e v i o u s m e t h o d s b a s e d on the Sokoloff p r i n c i p l e f o r two r e a s o n s . F i r s t , it e m p l o y s a c o u s t i c u l trasonic pulses that are directed toward obj e c t s p a c e f r o m the i m a g e p l a n e , a n d s e c o n d , the u l t r a s o n i c p u l s e g e n e r a t i n g t r a n s d u c e r a n d the p i e z o e l e c t r i c i m a g e c o n v e r s i o n s u r f a c e a r e the s a m e . O p e r a t i n g in a p u l s e echo mode, this electron beam scanned transc e i v e r tube o f f e r s the a d v a n t a g e of f a s t e r s c a n n i n g and, c o n s e q u e n t l y , r e d u c e d p i c t u r e frame time than similar mechanical 'C-scan' acoustic imaging systems. Its energy sensitivity i s p o o r e r t h a n s u c h m e c h a n i c a l s y s t e m s b y 2 to 4 o r d e r s of m a g n i t u d e . R e s o l u tion, s e n s i t i v i t y a n d a p e r t u r e a r e c o m p a r a b l e to p r e v i o u s l y r e p o r t e d c o n t i n u o u s w a v e i m a g e c o n v e r t e r t u b e s b a s e d on the Sokoloff p r i n c i p l e . T h e r a n g e of the p u l s e e c h o s y s t e m i s a f u n c t i o n of t r a n s m i t t e d p o w e r , i n t e r p u l s e i n t e r v a l , a n d p r o p a g a t i o n c o n s t a n t s of the o b j e c t s p a c e . (1775) Ultrasonic angular displacement s y s t e m and method of balancing the s a m e E n s l e y , D. L. US P a t e n t 3 , 4 4 6 , 714 (27 M a y 1969) T h i s is a s y s t e m f o r s h i f t i n g c e n t r e of m a s s of a b o d y to c e n t r e of b u o y a n c y . It c o m p r i s e s a m e t a l l i c f i l m on the b o d y a n d a c l o s e d c h a m b e r f o r e n c a s i n g it. An e l e c t r o l y t e in the c h a m b e r h a s a s p e c i f i c g r a v i t y c o r r e s p o n d i n g to t h a t of the b o d y , so t h a t w i t h i n the c h a m b e r it i s n e u t r a l l y b u o y a n t . T h e b o d y is p r e v e n t e d f r o m c o n t a c t i n g the c h a m b e r w a l l s , a n d t h e r e i s a m e a n s of s e n s i n g i t s c e s s a t i o n of r o t a t i o n , t h e r e b y m a r k i n g c o i n c i d e n c e b e t w e e n the c e n t r e of m a s s a n d the c e n t r e of b u o y a n c y . (1776) Fan beam a c o u s t i c Doppler n a v i g a t i o n system F a r r , H. K. US P a t e n t 3 , 4 3 6 , 721 (1 A p r i l 1969) ( F i l e d 16 J a n u a r y 1968) T h i s is a D o p p l e r t y p e v e l o c i t y m e a s u r i n g s y s t e m f o r u s e by v e s s e l s s a i l i n g in d e e p w a t e r . It c o m p r i s e s a t r a n s d u c e r a r r a y f o r p r o j e c t i n g a fan b e a m at a f o r w a r d a n g l e , a n d a r e c e i v i n g a r r a y f o r r e c e i v i n g on a f a n b e a m t r a n s v e r s e to t h a t of the t r a n s m i t t e d b e a m a n d w h i c h i n t e r s e c t s the l a t t e r at the o c e a n b o t t o m . A r e c e i v e r u t i l i z e s the D o p p l e r d i f f e r e n c e in f r e q u e n c y to d e t e r m i n e the v e l o c i t y of the v e s s e l . In one f o r m t h e r e a r e f o u r f a n beam intersections, pointing forward starb o a r d , f o r w a r d p o r t , aft s t a r b o a r d a n d aft p o r t , so t h a t both f o r w a r d a n d d r i f t v e l o c i t i e s c a n be measured. To overcome reverberation p r o b l e m s , g a t i n g i s e m p l o y e d , a n d the a d v a n t a g e s of p u l s e s a n d c o n t i n u o u s t r a n s m i s s i o n a r e c o m b i n e d b y u s i n g k e y i n g m e a n s to c h a n g e the t r a n s m i t t e d f r e q u e n c y c y c l i c a l l y . (1777) Size distribution of gas bubbles in w a t e r G a v r i l o v , L. R. Soviet P h y s i c s - - A c o u s t i c s , Vol 15, No 1 ( J u l y S e p t e m b e r 1969) pp 2 2 - 2 4 T h e r e s u l t s of m e a s u r e m e n t s of the s o u n d a t t e n u a t i o n i n d u c e d by gas bubbles a r e u s e d to find the s i z e d i s t r i b u t i o n of t h e b u b b l e s in l o n g - s t a n d i n g w a t e r a n d t a p w a t e r . (1778) Directional sonar system
Granfors, E. A., Loveless, D. L. and Boyle, C.F. US Patent 3,444,508 (13 M a y 1969) Filed 8 September 1967 A n underwater acoustic sensing system comprising a c o m m a n d activated floating buoy 64
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a s s e m b l y c o n n e c t e d to a s u b m e r g e d a c t i v e e l e c t r o n i c p r o b e a s s e m b l y c o n t a i n i n g hollow c e r a m i c c y l i n d e r s s t a c k e d in a v e r t i c a l i n terstitial array. Three transducer sections a r e u t i l i z e d h a v i n g an output l e v e l a n d r e l a t i v e p o l a r i t y r e l a t e d in a c c o r d a n c e w i t h the d i r e c t i o n f r o m w h i c h the a c o u s t i c s i g n a l b e ing r e c e i v e d a r r i v e s . One of the a c o u s t i c receiving patterns is omni-directional, and the o t h e r s a r e s i n e - c o s i n e d i p o l e p a t t e r n s w h i c h h a v e t h e c h a r a c t e r i s t i c of output l e v e l v a r i a t i o n with b e a r i n g s . T h e r e s u l t a n t t h r e e signals, and compass information constitute the p r i m a r y o u t p u t s of the s e n s i n g s y s t e m . (1779) Acoustic imaging in a turbid underwater environment
Green, P. S., Bellin, J. L. S., Knollman, G. C. JASA, Vol 44, No 6 (December 1968) pp 1719-1730 Theoretical an~i experimental studies are presented concerning underwater acoustic imaging in general with particular emphasis on acoustic visualization in highly turbid water. A derivation is made of the relationship b e t w e e n i m a g e - p l a n e a n d o b j e c t - p l a n e p r e s s u r e d i s t r i b u t i o n s in a n a c o u s t i c i m a g i n g system embodying a single spherical lens, a n d the t h e o r y is a p p l i e d to both d i f f u s e l y and specularly reflecting objects. The att e n u a t i o n a n d s c a t t e r i n g c o e f f i c i e n t s of s e a water containing various ocean-bottom sedim e n t s u s p e n s i o n s a r e d e t e r m i n e d ; it i s f o u n d t h a t f o r an a c o u s t i c f r e q u e n c y of 2 . 5 M H z ( e m p l o y e d in the e x p e r i m e n t a l w o r k ) , s e v e r a l hundred parts per million suspended sedim e n t c o n c e n t r a t i o n e f f e c t s an a c o u s t i c a t t e n u a t i o n t w i c e t h a t of s e a w a t e r a l o n e . A method for underwater acoustic image conv e r s i o n is d e s c r i b e d w h i c h i n v o l v e s a s a m p l e d m a t r i x of p i e z o e l e c t r i c e l e m e n t s . Two novel switching techniques are discuss e d f o r s e q u e n t i a l l y c o n n e c t i n g with high s e l e c t i v i t y the v a r i o u s s e n s o r e l e m e n t s to the output t e r m i n a l . T y p i c a l s h a d o w , f o c u s e d shadow, and backscatter acoustic images are displayed that were obtained with a 100-elem e n t c o l l i n e a r v e r s i o n of the i m a g e - c o n v e r sion s y s t e m . T h e c o l l i n e a r a r r a y h a s a s e n s i t i v i t y t h r e s h o l d of b e t t e r t h a n 1 0 - 1 O W / c m 2 a n d a r e s o l u t i o n on t h e o r d e r of 1 . 5 m m . S o m e of the i m a g e s w h i c h a r e p r e s e n t w e r e t a k e n a t a r a n g e of a p p r o x i m a t e l y 4 m in water containing several hundred parts per m i l l i o n of s u s p e n d e d d i a t o m a c e o u s e a r t h of m i c r o n p a r t i c l e s i z e . (1780) T h e r m a l r e l a ~ t i o n in nitrogen with wet carbon dioxide a s i m p u r i t y H e n d e r s o n , M. C., H e r z f n l d , K. F . , B r y , J . , C o a k l e y , R., C a r r i e r s , G. JASA, Vol 45, No 1 ( J a n u a r y 1969) p 1 0 9 - 1 1 4 A specially developed pressurized Kundt's t u b e h a s b e e n u s e d to m e a s u r e the N a p i e r ( r e l a x a t i o n ) f r e q u e n c y of n i t r o g e n in both binary and ternary mixtures with carbon d i o x i d e a n d w a t e r v a p o u r . C a r r i e d out a t a b o u t 175°C, w h e r e the r e l a x i n g s p e c i f i c h e a t of n i t r o g e n b e c o m e s r e a d i l y m e a s u r a b l e , the s e p a r a t e c o n t a m i n a n t s s h i f t the N a p i e r f r e q u e n c y u p w a r d b y a m o u n t s p r o p o r t i o n a l to their respective mole fractions: water vapour by 3 1 0 H z / m o l e - p e r c e n t , c a r b o n d i o x i d e b y 300Hz/mole-percent. When beth are present, the s h i f t i s n o t a b l y g r e a t e r a n d i s not l i n e a r in the m o l e f r a c t i o n . T h i s s y n e r g i s t i c e f f e c t i s e x p l i c a b l e on t h e o r e t i c a l g r o u n d s . P r e liminary results with heavy water vapour (D20) a s i m p u r i t y a r e a l s o g i v e n . Its e f f e c t i s a l s o n o n l i n e a r in the m i x e d i m p u r i t i e s . (1761) Variation of solubility of g a s e s in a liquid in a sound field K a p u s t i n a , O. A. Soviet P h y s i c s - - A c o u s t i c s , Vol 15, No 1 (July-September 1966) p p 5 4 - 5 9 T h e c a u s e s of the r e d u c t i o n in s o l u b i l i t y of g a s e s in l i q u i d s in a s o u n d f i e l d a r e c o n s i d e r e d . A t h e o r e t i c a l r e l a t i o n f o r the quasi-
e q u i l i b r i u m c o n c e n t r a t i o n e s t a b l i s h e d in u l t r a s o n i c d e g a s s i n g i s d e d u c e d on the b a s i s of the d i f f u s i o n i n t e r p r e t a t i o n of t h i s e f f e c t . T h e r e l a t i o n i s q u a l i t a t i v e l y c o n s i s t e n t with the e x p e r i m e n t a l d a t a , j u s t i f y i n g the p o s t u l a t e d m e c h a n i s m of the r e d u c t i o n in s o l u b i l i t y . (1782)
M e a s u r e m e n t s of the p r e s s u r e contours in p r e s s u r e p u l s e s generated by cavitation K u t t r a f f , von H., R a d e k , U. A c u s t i c a , Vol 21, No 5 (1969) pp 2 5 3 - 2 5 9 A collapsing cavitation bubble emits a press u r e p u l s e i n t o the s u r r o u n d i n g fluid. T h e t e m p o r a l a n d s p a c i a l c o n t o u r s of s u c h p u l s e s a r e t r e a t e d in the p r e s e n t p a p e r . A S c h l i e r e n observation method and an electroacoustic d e t e c t i o n m e t h o d w i t h the a i d of a s u i t a b l e microphone are employed for this purpose. C a v i t a t i o n w a s c a u s e d b y s o u n d in w a t e r a t 2 1 . 6 K H z a n d 27KHz. T h e r e r e s u l t s a m a x i m u m p r e s s u r e of s o m e l b a r a t a d i s t a n c e of l c m f r o m the i m p l o d i n g b u b b l e s . C a v i t a t i o n t r a c e s o b s e r v e d on i n d i u m s u r f a c e s y i e l d c o n c l u s i o n s a s to the a c t i n g m a x i m u m p r e s s u r e w h i c h m a y a m o u n t to at l e a s t 1 0 , 0 0 0 b a r . (1783) M a x i m u m s i d e - a s p e c t t a r g e t s t r e n g t h of a n individual fish L o v e , R. H. JASA, Vol 46, No 3 ( P a r t 2) ( S e p t e m b e r 1969) pp 7 4 6 - 7 5 2 E x p e r i m e n t s a r e d e s c r i b e d in w h i c h the t a r g e t s t r e n g t h s of a n u m b e r of i n d i v i d u a l f i s h were measured at various frequencies. The r e s u l t s of t h e s e e x p e r i m e n t s a r e c o m b i n e d with r e s u l t s f r o m s i x o t h e r s o u r c e s a n d a n e m p i r i c a l e q u a t i o n a p p r o x i m a t i n g the m a x i m u m s i d e - a s p e c t t a r g e t s t r e n g t h of a n i n d i v i d u a l f i s h d e t e r m i n e d f o r 1 ~< L / ~ ~ 100, w h e r e L i s t h e f i s h l e n g t h a n d ~ i s the a c o u s t i c w a v e l e n g t h . T h i s r e s u l t i s c o m b i n e d with a t h e o r e t i c a l e s t i m a t e of the r e s o n a n c e of a f i s h c o n t a i n i n g a s w i m b l a d d e r , to p r o d u c e a c u r v e a p p r o x i m a t i n g the m a x i m u m s i d e a s p e c t t a r g e t s t r e n g t h of a n i n d i v i d u a l b l a d d e r f i s h f o r L / ~ < 100. (1784)
T h e r m a l r e l a x a t i o n in h u r a l d a i r Monk, R. G. JASA, Vol 46, No 3 ( P a r t 2) ( S e p t e m b e r 1969) pp 5 8 0 - 5 8 6 A theoretical and experimental investigation of the m o l e c u l a r a b s o r p t i o n p r o c e s s in a i r h a s b e e n c a r r i e d out w i t h p a r t i c u l a r r e f e r e n c e to the v a r i a t i o n of N a p i e r f r e q u e n c y (fmax) w i t h w a t e r - v a p o u r c o n c e n t r a t i o n (h'). It t u r n s out t h a t the r e l a t i o n s h i p b e t w e e n t h e s e two q u a n t i t i e s i s a q u a d r a t i c o n l y a t v e r y low h u m i d i t i e s a n d that, o v e r the r e s t of the h u m i d i t y r a n g e , the g e n e r a l r e l a t i o n ship derived here is best approximated by an e q u a t i o n of the f o r m f m a x = c o n s t h 'x, w h e r e 1 ~ x ~ 2. C r i t i c a l e x a m i n a t i o n of p r e v i o u s t h e o r e t i c a l r e l a t i o n s h i p s s h o w s t h a t the r a t e of r e s o n a n t i n t e r c h a n g e of e n e r g y b e t w e e n oxygen and water vapour has been underest i m a t e d b e c a u s e of the q u a d r a t i c a p p r o x i m a tion. R e a s s e s s m e n t of t h i s q u a n t i t y on the b a s i s of the a n a l y s i s h e r e i n y i e l d s a m o r e realistic value that is more consistent with p r e v i o u s e x p e r i m e n t a l f i n d i n g s in o x y g e n a n d c l o s e r to w h a t one w o u l d e x p e c t f r o m theoretical calculations. Details are also g i v e n of a n u m e r i c a l m e t h o d of c a l c u l a t i n g Napier frequently directly from measured v a l u e s of m o l e c u l a r a b s o r p t i o n . (1785) E x p e r i m e n t s on the acoustic modulation of large-amplitude waves M u i r , T. G. a n d Blue, J. E. JASA, V o l 46, No 1, P a r t 2 ( J u l y 1969) pp 2 2 7 - 2 3 2 A s e r i e s of e x p e r i m e n t s w e r e p e r f o r m e d to study the parametric relationship between two h i g h - f r e q u e n c y c a r r i e r w a v e s a n d the difference-frequency wave created by their nonlinear i n t e r a c t i o n . M e a s u r e m e n t s w e r e m a d e in a f r e s h w a t e r l a k e in the f a r f i e l d of
Granfors, E. A., Loveless, D. L. and Boyle, C.F. US Patent 3,444,508 (13 M a y 1969) Filed 8 September 1967 A n underwater acoustic sensing system comprising a c o m m a n d activated floating buoy 64
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1970
a s s e m b l y c o n n e c t e d to a s u b m e r g e d a c t i v e e l e c t r o n i c p r o b e a s s e m b l y c o n t a i n i n g hollow c e r a m i c c y l i n d e r s s t a c k e d in a v e r t i c a l i n terstitial array. Three transducer sections a r e u t i l i z e d h a v i n g an output l e v e l a n d r e l a t i v e p o l a r i t y r e l a t e d in a c c o r d a n c e w i t h the d i r e c t i o n f r o m w h i c h the a c o u s t i c s i g n a l b e ing r e c e i v e d a r r i v e s . One of the a c o u s t i c receiving patterns is omni-directional, and the o t h e r s a r e s i n e - c o s i n e d i p o l e p a t t e r n s w h i c h h a v e t h e c h a r a c t e r i s t i c of output l e v e l v a r i a t i o n with b e a r i n g s . T h e r e s u l t a n t t h r e e signals, and compass information constitute the p r i m a r y o u t p u t s of the s e n s i n g s y s t e m . (1779) Acoustic imaging in a turbid underwater environment
Green, P. S., Bellin, J. L. S., Knollman, G. C. JASA, Vol 44, No 6 (December 1968) pp 1719-1730 Theoretical an~i experimental studies are presented concerning underwater acoustic imaging in general with particular emphasis on acoustic visualization in highly turbid water. A derivation is made of the relationship b e t w e e n i m a g e - p l a n e a n d o b j e c t - p l a n e p r e s s u r e d i s t r i b u t i o n s in a n a c o u s t i c i m a g i n g system embodying a single spherical lens, a n d the t h e o r y is a p p l i e d to both d i f f u s e l y and specularly reflecting objects. The att e n u a t i o n a n d s c a t t e r i n g c o e f f i c i e n t s of s e a water containing various ocean-bottom sedim e n t s u s p e n s i o n s a r e d e t e r m i n e d ; it i s f o u n d t h a t f o r an a c o u s t i c f r e q u e n c y of 2 . 5 M H z ( e m p l o y e d in the e x p e r i m e n t a l w o r k ) , s e v e r a l hundred parts per million suspended sedim e n t c o n c e n t r a t i o n e f f e c t s an a c o u s t i c a t t e n u a t i o n t w i c e t h a t of s e a w a t e r a l o n e . A method for underwater acoustic image conv e r s i o n is d e s c r i b e d w h i c h i n v o l v e s a s a m p l e d m a t r i x of p i e z o e l e c t r i c e l e m e n t s . Two novel switching techniques are discuss e d f o r s e q u e n t i a l l y c o n n e c t i n g with high s e l e c t i v i t y the v a r i o u s s e n s o r e l e m e n t s to the output t e r m i n a l . T y p i c a l s h a d o w , f o c u s e d shadow, and backscatter acoustic images are displayed that were obtained with a 100-elem e n t c o l l i n e a r v e r s i o n of the i m a g e - c o n v e r sion s y s t e m . T h e c o l l i n e a r a r r a y h a s a s e n s i t i v i t y t h r e s h o l d of b e t t e r t h a n 1 0 - 1 O W / c m 2 a n d a r e s o l u t i o n on t h e o r d e r of 1 . 5 m m . S o m e of the i m a g e s w h i c h a r e p r e s e n t w e r e t a k e n a t a r a n g e of a p p r o x i m a t e l y 4 m in water containing several hundred parts per m i l l i o n of s u s p e n d e d d i a t o m a c e o u s e a r t h of m i c r o n p a r t i c l e s i z e . (1780) T h e r m a l r e l a ~ t i o n in nitrogen with wet carbon dioxide a s i m p u r i t y H e n d e r s o n , M. C., H e r z f n l d , K. F . , B r y , J . , C o a k l e y , R., C a r r i e r s , G. JASA, Vol 45, No 1 ( J a n u a r y 1969) p 1 0 9 - 1 1 4 A specially developed pressurized Kundt's t u b e h a s b e e n u s e d to m e a s u r e the N a p i e r ( r e l a x a t i o n ) f r e q u e n c y of n i t r o g e n in both binary and ternary mixtures with carbon d i o x i d e a n d w a t e r v a p o u r . C a r r i e d out a t a b o u t 175°C, w h e r e the r e l a x i n g s p e c i f i c h e a t of n i t r o g e n b e c o m e s r e a d i l y m e a s u r a b l e , the s e p a r a t e c o n t a m i n a n t s s h i f t the N a p i e r f r e q u e n c y u p w a r d b y a m o u n t s p r o p o r t i o n a l to their respective mole fractions: water vapour by 3 1 0 H z / m o l e - p e r c e n t , c a r b o n d i o x i d e b y 300Hz/mole-percent. When beth are present, the s h i f t i s n o t a b l y g r e a t e r a n d i s not l i n e a r in the m o l e f r a c t i o n . T h i s s y n e r g i s t i c e f f e c t i s e x p l i c a b l e on t h e o r e t i c a l g r o u n d s . P r e liminary results with heavy water vapour (D20) a s i m p u r i t y a r e a l s o g i v e n . Its e f f e c t i s a l s o n o n l i n e a r in the m i x e d i m p u r i t i e s . (1761) Variation of solubility of g a s e s in a liquid in a sound field K a p u s t i n a , O. A. Soviet P h y s i c s - - A c o u s t i c s , Vol 15, No 1 (July-September 1966) p p 5 4 - 5 9 T h e c a u s e s of the r e d u c t i o n in s o l u b i l i t y of g a s e s in l i q u i d s in a s o u n d f i e l d a r e c o n s i d e r e d . A t h e o r e t i c a l r e l a t i o n f o r the quasi-
e q u i l i b r i u m c o n c e n t r a t i o n e s t a b l i s h e d in u l t r a s o n i c d e g a s s i n g i s d e d u c e d on the b a s i s of the d i f f u s i o n i n t e r p r e t a t i o n of t h i s e f f e c t . T h e r e l a t i o n i s q u a l i t a t i v e l y c o n s i s t e n t with the e x p e r i m e n t a l d a t a , j u s t i f y i n g the p o s t u l a t e d m e c h a n i s m of the r e d u c t i o n in s o l u b i l i t y . (1782)
M e a s u r e m e n t s of the p r e s s u r e contours in p r e s s u r e p u l s e s generated by cavitation K u t t r a f f , von H., R a d e k , U. A c u s t i c a , Vol 21, No 5 (1969) pp 2 5 3 - 2 5 9 A collapsing cavitation bubble emits a press u r e p u l s e i n t o the s u r r o u n d i n g fluid. T h e t e m p o r a l a n d s p a c i a l c o n t o u r s of s u c h p u l s e s a r e t r e a t e d in the p r e s e n t p a p e r . A S c h l i e r e n observation method and an electroacoustic d e t e c t i o n m e t h o d w i t h the a i d of a s u i t a b l e microphone are employed for this purpose. C a v i t a t i o n w a s c a u s e d b y s o u n d in w a t e r a t 2 1 . 6 K H z a n d 27KHz. T h e r e r e s u l t s a m a x i m u m p r e s s u r e of s o m e l b a r a t a d i s t a n c e of l c m f r o m the i m p l o d i n g b u b b l e s . C a v i t a t i o n t r a c e s o b s e r v e d on i n d i u m s u r f a c e s y i e l d c o n c l u s i o n s a s to the a c t i n g m a x i m u m p r e s s u r e w h i c h m a y a m o u n t to at l e a s t 1 0 , 0 0 0 b a r . (1783) M a x i m u m s i d e - a s p e c t t a r g e t s t r e n g t h of a n individual fish L o v e , R. H. JASA, Vol 46, No 3 ( P a r t 2) ( S e p t e m b e r 1969) pp 7 4 6 - 7 5 2 E x p e r i m e n t s a r e d e s c r i b e d in w h i c h the t a r g e t s t r e n g t h s of a n u m b e r of i n d i v i d u a l f i s h were measured at various frequencies. The r e s u l t s of t h e s e e x p e r i m e n t s a r e c o m b i n e d with r e s u l t s f r o m s i x o t h e r s o u r c e s a n d a n e m p i r i c a l e q u a t i o n a p p r o x i m a t i n g the m a x i m u m s i d e - a s p e c t t a r g e t s t r e n g t h of a n i n d i v i d u a l f i s h d e t e r m i n e d f o r 1 ~< L / ~ ~ 100, w h e r e L i s t h e f i s h l e n g t h a n d ~ i s the a c o u s t i c w a v e l e n g t h . T h i s r e s u l t i s c o m b i n e d with a t h e o r e t i c a l e s t i m a t e of the r e s o n a n c e of a f i s h c o n t a i n i n g a s w i m b l a d d e r , to p r o d u c e a c u r v e a p p r o x i m a t i n g the m a x i m u m s i d e a s p e c t t a r g e t s t r e n g t h of a n i n d i v i d u a l b l a d d e r f i s h f o r L / ~ < 100. (1784)
T h e r m a l r e l a x a t i o n in h u r a l d a i r Monk, R. G. JASA, Vol 46, No 3 ( P a r t 2) ( S e p t e m b e r 1969) pp 5 8 0 - 5 8 6 A theoretical and experimental investigation of the m o l e c u l a r a b s o r p t i o n p r o c e s s in a i r h a s b e e n c a r r i e d out w i t h p a r t i c u l a r r e f e r e n c e to the v a r i a t i o n of N a p i e r f r e q u e n c y (fmax) w i t h w a t e r - v a p o u r c o n c e n t r a t i o n (h'). It t u r n s out t h a t the r e l a t i o n s h i p b e t w e e n t h e s e two q u a n t i t i e s i s a q u a d r a t i c o n l y a t v e r y low h u m i d i t i e s a n d that, o v e r the r e s t of the h u m i d i t y r a n g e , the g e n e r a l r e l a t i o n ship derived here is best approximated by an e q u a t i o n of the f o r m f m a x = c o n s t h 'x, w h e r e 1 ~ x ~ 2. C r i t i c a l e x a m i n a t i o n of p r e v i o u s t h e o r e t i c a l r e l a t i o n s h i p s s h o w s t h a t the r a t e of r e s o n a n t i n t e r c h a n g e of e n e r g y b e t w e e n oxygen and water vapour has been underest i m a t e d b e c a u s e of the q u a d r a t i c a p p r o x i m a tion. R e a s s e s s m e n t of t h i s q u a n t i t y on the b a s i s of the a n a l y s i s h e r e i n y i e l d s a m o r e realistic value that is more consistent with p r e v i o u s e x p e r i m e n t a l f i n d i n g s in o x y g e n a n d c l o s e r to w h a t one w o u l d e x p e c t f r o m theoretical calculations. Details are also g i v e n of a n u m e r i c a l m e t h o d of c a l c u l a t i n g Napier frequently directly from measured v a l u e s of m o l e c u l a r a b s o r p t i o n . (1785) E x p e r i m e n t s on the acoustic modulation of large-amplitude waves M u i r , T. G. a n d Blue, J. E. JASA, V o l 46, No 1, P a r t 2 ( J u l y 1969) pp 2 2 7 - 2 3 2 A s e r i e s of e x p e r i m e n t s w e r e p e r f o r m e d to study the parametric relationship between two h i g h - f r e q u e n c y c a r r i e r w a v e s a n d the difference-frequency wave created by their nonlinear i n t e r a c t i o n . M e a s u r e m e n t s w e r e m a d e in a f r e s h w a t e r l a k e in the f a r f i e l d of