'Ji- 



ll WDBOOK (II- l'II\s|i il i IGY 



NFAROPHYSIOLOGY III 



mooo 



fig. i. Articulation score for continuous speech, switched 

 periodically at various frequencies from one ear to the other in 

 one subject. For each ear the proportion of the period occupied 

 l>\ speech is y> per iciil. the rein. under being silent. Voltage 

 across telephones, 0.087 v'olt ' ms "hen speech is uninterrupted. 

 [From ( Iheri j & Tayloi (24) 



neurological correlates have been adduced, e.g. 

 asymmetry in electrophysiological response in the 

 auditory cortices consequent upon variation in 

 locus of sound-source (109, [33), but their explanatory 

 value is limited. No convincing explanation of 

 binaural speech perception at the neurophysiological 

 level can yet be given. 



Aural 'Monitoring' oj Speech 



I he role of aural 'monitoring 1 in control of speech 

 lias been well broughl out in a number of recent 



studies. In 1950, Lee (74) reported that if a subject's 

 own speech is played back to him through closely 

 fitting headphones with a delay of 0.07 to o. 10 sec. 

 ('delayed side-tone'), striking disturbances in speech 

 not uncommonly result. The voice becomes louder; 

 words, syllables and phonemes are repeated, words 

 may be mispronounced; and the overall speech rate 

 is retarded. In some cases, definite sitjns of anxiety 

 and distress, e.g. palmar sweating, arc in evidence. 

 These findings led Lee to conclude that aural feedback 

 normally operates as governor of the overall speech 

 rale. Whereas some subjects appear to slow down 

 automatically under conditions of delayed speech 

 playback, others require practice to achieve the 

 proper cadence. It is in these latter that erratic and 

 stuttering speech may be produced. 



Lee's findings have been confirmed and extended 

 by several other investigators (3, 4, 8, 9, 35). Black 

 (8) has reported that both rate and intensity of oral 

 reading are affected by 'delayed side-tone." In 

 general, he finds, speed of reading is progressively 

 retarded as the increments of delay arc increased 

 through the range o to 0.18 sec, with a particularly 

 marked effect .is delay is increased from 0.03 to 0.06 

 sec. This mighl suggest that a delay rousrhlv the same 

 as the duration of a phoneme is of particular signifi- 

 cance in retarding the fluency of speech. Further, 

 the fact that the longest reading times are found with 

 delays of 0.18 sec. might be held to indicate .1 relation- 

 ship between syllable duration and the effects of 

 "delayed side-tone.' Black has also adduced evidence 

 that the decreased rate of speaking; provoked by 



-a* -03 -02 -01 01 02 6~3 04 



TIME DISPLACEMENT Of HiGmTEAB MESSAGE.OEL ATivE TO LEf T E AS MESSAGEmSEC 



100 



80 - 



BO 



20 



SIGNALS PERCEIVED . 



ONE ACOUSTIC / 



ELO (SAME CURVE ' 



G 10(a)) / 



Signals perceived 

 as separate fie 



'E0-. / 



LOS \ / 



- 



5 10 15 20 25 30 



TIME DELAY OF RIGHT EAR MESSAGE RELATIVE TO LEFT 

 EAR MESSAGE- mSEC 



in. . Left: Binaural perception of speech direction right 01 left at various time displacements, 

 ofmc agi to thi two ears Right Binaural perception of one or of two acoustic fields. FromCherrj 

 >s rayloi 24 





