TOTAl 10

CENTRE FOR NEWFOUNDLAND STUDIES

TOTAl OF 10 PAGES ONLY MAY BE XEROXED

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COMBINm_a SENSORY INFORMATION

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FROM _!WO SEP~E

CRITICAL BANDS

by

© Martin .Erhard Rickert, _·, B .Sc.

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fulfillment

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of the requiicmentS for the degree of

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Master of Science

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D_epartrMTJt, ^• of Psychology

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Memorial

Uiai.ver~lty of Newfoundlaird

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^{. August. 191!7}

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St. John•s · · _{• I} New}'oUndland.

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Permission-has been granted to the Natianal' Library of .Canada '·to ai crof,i

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this thesis and 'to .. lend. or sell copies of the ·film.

t\ ·The autho~? (.copyright o~n~r)

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· · . . publ)reation ' rights·~ .. ~nd

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. L'autoriaation a ete' accordee . .A ).a Bibll.thequo nation_al~ .;(

~ du · Canada de aHcr.ofilmer

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ABSTRACf

This ·.study investigated how subjeCts. combine auditory signals and .

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~ nois~. f'r9m two separate frequcncy-scleetive . channels; or critical bands. In

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the fitst experimeti~ Witeners 'Vere··traine4· -~o detect a 0.~

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to~e in -a ·co.ritinuops .. b~kgro~~d o_f ·noise.' Then. :without informin~·lis_~ners. · a· 1.3.Jiz ·tone

w~. ~d

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th~ dctc~~bulty

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twO:. tone complex was-no-b·eu~r-tlfall thc--~tectabillty·· of-the O~S1dlz sj~al. . • ...

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· was· reinoy~ ^and ,.PerfOnil~Ce. dropped to, or 'below, the-origm~· lcvck-, . . . .. : -:~

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use :. ci~ .

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: s~ngle- o~ :m~~ple-b~d listening. s~tegy. ^·.In qnter .to de~nnine more · ·. :. . . .. .-.::.~:

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·._. about.'how _{. {·} information _{. .} .from· widely _{. .} sep~~

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^. Critical·· bands is cotnbincd; ^{. . . ·.} ~ ^{. ( · .. . .} ~:~

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two· mathematical.·m~is ·we~ considered. The llf{d'nnanon .Integration . · :~j.

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_'

(6~n~

1956}·: asSumes· _. .that _" siSnal

~d ~olse ·. ·c~ergy --

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fro~. ~divid~al

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· - ~ontras~ the· ckcision thTeshol~ : ~1 · (Scbaf~r and QBles,.-1949) : ~st~lates · · ··.-11

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that

indCpendent decisions ·are. made. about .·the information in ~ach chamici;· · · .-:. ·,.;1

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^{that the·} O~tcomcs _{·. . ...} of

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^decisions_. ^{. iu:e} _{. .} GOmb~ed _. ^according _. lO an · ·'

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· declsion ^{' .} rule. ^{. .}

Data

^{from . . .the . first '} experiment ^{. . .. ...} 8l'e ^{~ "} consistent ^{. .:} with ^. the ^'

· .. inf~rmati~~-

• tntei,ration .

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using

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these ~Is; a· s~ond, -~more sensitive, exi>erimept was ~igned. In this

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i study shows that neither-the infonnatio~ ·integration :rilodel nor .. the decision·

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threshold mOdel explains how· .listeners combine· inforinatiori '·from · tvio : ·

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· .... . ., ' . ACkNOWLEDGEMENTS

Firstr .I ·~ould like _to .·gratefully acknowled~ the encouragement, and

uilheslsta~g

assistance

dovided

^:by

· m~

supervisor· Michael A. Zagorski .

Through~~t

^..

ihz_ co~

^{of thls' study,}

hi~ "s~~a" ~vice,

whlch has· often •

extended beyond the domaiti · of scien~e, has proyen invaluable. I sin~ercly . . · . . . · r"" . · ' · .

hope that ~ will remain my mentor and. trusted friend _{~ . . ...} in year§ to· come . I;d.

like

·also to

thank

the members

of

my thesis committee,: Mictt el · ...

• • • 0 • • •• •

• .• • • • . ; : .: . • • • '.. ' . . ( . f"'' . \- • : • • •&- . •. . • • • • ••

Bruce-Lockhart' and Russ A~ for. cri~cally rca~g, and commc· ting on. ;

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·.an -earlier ·.version· of this thesiS. To ·MPBL, I. extend. a· funhcr and most ·. ·.

.. • •• ' • f • • ' '' • • t •' - • • '' I ,· ' ", •, ,• •• - - •· •• ~ ^{•, •}

ctCsel'Ved ·

thanks! - His :

^guidance:

and

-support has ·been, and

· will .

continue· to ~·

• : • • • • ( ·., ,· ' • • • ,' • • • I o • '

be, . greatly ·. appieclate<i · / · · _{· ... .}

•• • • J, - '

This

_• th~~i~ _• is dedicated _{f •} to the "gang" 0 • at home .. who have ··remained'

a

constanf.

~ource

^{. of}

ins~iratio~..

^{. The .}

com~letion

^.of.

^{this .} proje~t

^{wo.uld 'not' ·.}

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· have 'been ~ssible witltout their unconditionill support.-

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Table of Contents

Abstract ·:··\···············~···!········

Acknowledgements

... ... . .... . ... . ... . . . . ... ... ... ... ... ...

List of Tables ···•t~••···:

...

^~

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L. ^{IS • . t} of 'Ft·gure· . .s .

... . . . ... . ... ... ...

INTRODUCTION •••••••••••r;,,,,,. .. ,.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,.,,,,,,,,,,,,,.,,,,,,,,

~· · A~ditorY ·filtering:· T~ crltic.al band

B~ Single~

^{and. multiple-.}band ·listening

-··· ···~···· ···

I 1. •.

Dete~tion) J/.

unUpected,:

low~ pro~ability

·sigtia/s . .. : ...•.• ;_ .... ,.': .... .

... 2. ··Detecti~n

_{~ ·. . ~} ^·of _. ^·muJtico",/Jtinent _{. ' ~ : '} signals_{. .} ·.: ... .' .•...

~···~

_'

···~···

^{... ··}

. . . 3. Uncertain frequency ·-detection

n.

EXPE~Nf.· ^..

i.

^{B,locks ·Using}

· ,iie

s~ sig",wl (hroug~u't · : .. : .... ·.~.

A .. Methods .;.:.: ..•..•... : .. ~~ ... :: ... ; ••... :.~: •... ~ .. : .. .-... ·.~··

... . ... ... ... ....

1 .. Obse'f.'V'efs _·. ••••••••••••. ••••••••••••••••••••••••••••••••••• · ... " .

.

2~ · Apparatw ..... · ... -.... . ,....

. 3. Stimuli.

··· ····.···~··· ··· ··· ···~.·· ····~

4. Trial, . block~ and session . design

S. P ._f .. pee· d"·e· , · . · · · . '

I . . . . I t t tttt t t t tt tt t l t l,tl tt t t t t t t,t t l t e e e t t t t e t t t : t e t e te te t t • e t t e e tet tt t tt t t tee t t e t t t t t t • t t f " t

.... ... ... . .... ....

B. Results. • .••. · •... · ... ~ .. : ..•...•.. ~ ...•..••....•.... · ...•... ~ ... ~.

'---~·\ C.'· Discus~i~.n of Experiment 1

. ... . . . ... . . . . ... ... ...

m.

EXPERIMENT ·_.

.

. 2. Blocks· . :with a niixture . .. ^... of signal . rypes

A.

.Proceduxe ... : •.••••••••••• ~ ••••.• ~···; ••••••.••.••••••••••••••••••••.•••..•••••••••••••••••••

. . ·. . . .

"

^{' .} . .

.

B. Results •.... ~ ... ~··· .. ···: ... .

· C. DiscUssiOn· of Bxj)crimcni. 2 .... , .•...•...•... ; ...•... -.•. · .•...

. . .

-

. ^{\ .} . . . . ·. ^~ . '

IV •. OONnUSION .••.• ,: •. ~ ....•...• ·; ... ~ ....• ~ .... · .. · ...•. ~ ...•...•...

t t • . I •

REFERENCES

··~·····.···· .. ········\·.······~···.···~·~

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ii iv vi vii 1

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7 9

10

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18 18 19 20·

21 24 26 30 30 31

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...

·.·

- Table 1. OOtai~d values

LIST ·-~OF T ~LES

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of d' from Experiment I.

cTable 2. Summary 'of th~ analysis of ExPeriment 2 .

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INTRODUCI'ION

The. main advantage ~ntroduced by signal detection theory (Peterson,

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Birdsall, and Fox, 1954) to auditory psychophysics, is that it provides a

• framework for distinguishing between sensory and decision proce~ses.

-

This

frnmework includes empirical· and analytic methods that pennit listeners' sensitivity to be estimated independent of non-sensory variables.

Conseque1_1tly, signal detection methods have been used to ·address many

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substantive . issues about ·auditory · signal P,iocessing.

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·iss~

^that bas received ·consl.rable

atte~tion,

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utilize

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. detecting' signalS in noise.

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^suggCsts

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listeners c!"' adopt a listening "strategy" that

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the requirements of a· specific task · (Swets, -1963, 1984). ^{Thus /} informatiQn is restricted to a relatively

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narrow part '·of the spectrun/. listeners have the ability to process that

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infonnation wmle,

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the rest. If, however, infonnation anives in several spectral region/, there are a number of ways in which it can be

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processed.

Presented h re are tWo expCrlments. The first investigates a sutijects'

• ~bility to ~ transitions in .. listening strate~ when the signal changes

· uncxpcc,~ th~ second

investigates

performance when ·

^{the samC} Slratcgy

IJl~ used for different signals. In addition., the~e e~periments te~t vl¢o~s. assumptions about how listeners combine auditory infonnation in

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order to make a decisiof! concerning the. presence or ab$ence of a brief tonal signal embedded in noise.

A. Auditory ftlterlng: The critical band ·

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U~likc the visual syste~, whi~h integrates energy at different spectral '

. frequencies to proVide th~ sensation of a single color, the auditory system allows us ·to ,resolve,

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separate, individual s~tral c~mponents of a

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~omplex sound (Green ~d. Sw~ts, 1974). This ability stems primaril): from the faCt that the auditory stimulps is' filtered ~t various levels . of processing .

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For· example,_ physiologic!ll··experlments conducted by von BcJcesy (196lb)

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show that for

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^{'pure /~ound} of a given. (requency' there is a region of

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maximum vibratory msponse_{. .} · along the . ·builar membrane (BM). ^. The mechanical displae_~ment of. the BM is then conve~ to a distribu~oh of neural activity across the c;ochlear fiQers (Sachs and Kiang, 1968).

However, electrophysiologieal measurements in4icate that

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^{. . ...} this excitation ^. pattern. is not perfectly correlated with· mechanical ·activity in ihe cochle~.

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The' fact ·that displacement patterns along the B~ do . not match the .

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~queri~~- s~tivi_ty exhibi_~ ^by· the disch~ge ch~cteristics ^{of the} Vlllth . . nerve has led

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the--hypothesis that a "second"

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exists betw,een the

b~ilar memb~e

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initial segment. of. the auditory nerves· (Evans

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Wilson,. 1973). · 4

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'Psychophysical . studies have also provided strong evidence for the

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existence of audit9ry filtering, ~d, have been ·used to determine some

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important filter ch~ctcrlstics, · including bandwidth and sha~.- The· width

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