Auditory-nerve and energy-detection models of temporal summation in hearing: a theoretical and experimental investigation

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ABSTRACT

Experimental e x t e n s i o n s and t h e o r e t i c a l e x p l a n a t i o n s o f a p s y c h o a c o u s t i c experiment concerning temporal summation o f human h e a r i n g a r e i n v e s - t i g a t e d . The experiment h a s t h e w e l l - e s t a b l i s h e d r e s u l t t h a t , c e t e r i s p a r i b u s , a b r i e f t o n e b u r s t i s more r e a d i l y oletected t h a n a b r i e f gap i n a t o n e . Two models, one b a s e d on t h e n e u r o e l e c t r i c a l a c t i v i t y o f t h e ;ud:-- t o r y n e r v e and one on e n e r g y - d e t e c t i o n t h e o r y , a r e p r e s e n t e d and developad i n d e t a i l : b o t h a r e shown c a p a b l e o f p r e d i c t i n g t h e r e s u l t o f t h e b u r s t s

1

and gaps e x p e r i r ~ e n t

.

Seven e x p e r i m e n t s a r e - e p o r t e d . Experiment 1 founc!

t h e r e a c t i o n t i m e t o t h e s t a r t o f a f a i n t t o n e embedded i n n o i s e g e n e r a l l y

I s h o r t e r t h a n t h a t t o i t s end. Experiment 2 (:xamined t h e e f f e c t o f r i s e /

decay time on t h e d e t e c t a b i l i t y o f b s i e f b u n t s o f , o r gaps i n , broadband n o i s e : when t h e energy change was c o n s t a n t , l h e r e was no e f f e c t e x c e p t a t l o n g (100 msec) r i s e / d e c a y t i m e s . Experimen;.~ 3 and 4 a s s e s s e d t h e d e t e c - t a b i l i t y o f b u r s t s o f , and gaps i n , a t o n e e ~ l b e d d e d i n n o i s e where e n e r g y change t o n o i s e power p e r c y c l e was c o n s t a n t b u t d u r a t i o n v a r i e d . The d a t a d e m o n s t r a t e t h a t t h e e f f e c t o f d u r a t i o n on d e t e c t a b i l i t y was d i f f e r e n t f o r b u r s t t h a n gnp e v e n t s , a r e s u l t p r e d i c t e d by b o t h models. Experiment 3 showed t h a t , when t h e energy i n and d u r a t i o n o f a t o n e b u r s t i n n o i s e were c o n s t a n t b u t t h e temporal d i s t r i b u t i o n o f t h e b u r s t energy v a r i e d , d e t e c - t a b i l i t y remained unchanged. The r e p e t i t i o n r a t e o f n o i s e b u r s t s and gaps i n c o n t i n u o u s n o i s e was v a r i e d w i t h o u t e f f e c t on d e t e c t a b i l i t y i n Experi- ment 6. Bursts,however, were c o n s i s t e r l t l y mcre d e t e c t a b l e t h a n g a p s .

Experiment 7 compared the dctectability of increments and decrcments of

a

continuous tone embedded

i n

noise. The quantitative predictions of the

two models are compared with the data resulting from Experiments 3,

5,

and 7. The qualitative results of these and the other experiments are

also discussed in terms of their theoretical implications. Taken all to-

gether, the experiments do not definitely favour either model over the

other.