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r e s i d u a l h e a r i n g t ha t at l e a s t to some degree i s p o t e n - t i a l l y u sab le w i t h a u d i t o r y t r a i n i n g and w i t h a p r o p e r l y chosen s e n s o r y a i d I n ano the r a p p r o a c h the n o n a c o u s t i c the a c o u s t i c s i g n a l i s t r a n s f o r m e d and p r e s e n t e d i n ano the r s e n s o r y m o d a l i t y The two types of s e n s o r y a ids a s s o c i a t e d w i t h these approaches a r e d i s c u s s e d b r i e f l y b e l o w A c o u s t i c A i d s C o m p l e t e absence of a u d i t o r y r e sponse a m o n g the deaf p o p u l a t i o n i s v e r y r a r e A s a consequence the e f f o r t to take advantage of r e s i d u a l h e a r i n g has l e d t o the d e v e l o p m e n t of t w o types of s e n s o r y a ids i n the a c o u s t i c c l a s s The m o r e c o m m o n one i n v o l v e s n o t h i n g m o r e t han sound a m p l i f i c a t i o n as p r o v i d e d b y c o n v e n t i o n a l h e a r i n g a ids the a c o u s t i c e n e r g y b e i n g d e l i v e r e d e i t h e r b y a i r - c o n - d u c t i o n o r b y b o n e - c o n d u c t i o n r e c e i v e r s The r a t i o n a l e f o r t h i s t ype of a i d has m e r i t Some a u d i t o r y i n f o r m a t i o n i s b e t t e r t h a n none , and the a ids a r e r e a d i l y a v a i l a b l e F o r m a n y p r o f o u n d l y deaf the a u d i t o r y i n f o r m a t i o n p r o v i d e d w i l l i n c l u d e m i n i m a l c h a r a c t e r i s t i c s of v o w e l s i n t o n a t i o n and r h y t h m as w e l l as v a l u a b l e o r i e n t a t i o n c lues A s no ted above the a c o u s t i c a m p l i f i c a t i o n p r o v i d e d b y these a ids i s of g r e a t b e n e f i t t o those w i t h l e s s s eve re h e a r i n g i m p a i r m e n t Some i n f o r m a t i o n on the o p t i m a l a c o u s t i c de - s ign of s o u n d - a m p l i f y i n g a ids i s a v a i l a b l e * H o w e v e r f u r t h e r e x t e n s i v e r e s e a r c h i s r e q u i r e d on o p t i m a l f r e q u e n c y r e sponse s on the use of a u t o m a t i c g a i n c o n t r o l and output l i m i t i n g on c u s t o m f i t t i n g on the use of b i n a u r a l a ids on p o r t a b i l i t y and on the d e s i g n of g r o u p a ids f o r use i n c l a s s - r o o m s of h e a r i n g - i m p a i r e d c h i l d r e n The a c o u s t i c s of m a n y c l a s s r o o m s a r e u n s u i t a b l e f o r m a k i n g the bes t use of h e a r i n g a ids f u r t h e r e x p e r i m e n t s on and d i s s e m i n a t i o n of i n f o r m a t i o n about o p t i m a l c l a s s r o o m a c o u s t i c s a r e needed A n i m p o r t a n t a d d i t i o n a l c o n s i d e r a t i o n i n the de s ign of such a ids i s tha t t oday t h e y a r e o f t e n p l a c e d on bab ie s i n t h e i r f i r s t f e w m o n t h s of l i f e I t i s no t s u f f i c i e n t - 4 -
