Reliability of categorical loudness scaling in the electrical domain.
OBJECTIVE
In categorical loudness scaling (CLS), subjects rate the perceived loudness on a categorical scale with alternatives. ISO 16832 describes an internationally standardized CLS procedure for the acoustical domain. This study focuses on the reproducibility of CLS following the recommendations of ISO 16832 using electrical stimuli presented to cochlear implant (CI) users.


METHODS
Repeated CLS measurements were done using single-electrode stimuli at four electrode positions. Loudness growth functions (LGFs) described loudness as a function of level (μA). LGF shapes were characterized with an exponential b parameter. The reproducibility of the b parameter and inter-session intra-subject differences in percentage dynamic range (DR) between 'Very Soft' and 'Loud - Very Loud' levels were analysed.


METHODS
Ten CI users.


RESULTS
Inter-session differences did not significantly differ between loudness categories or electrode positions. Across loudness categories the standard deviation of inter-session differences equalled 7.2%DR. The reproducibility of LGF shapes was moderate (r = 0.63). The LGFs of 43% of the measured electrodes significantly deviated from linear (nonzero b parameter).


CONCLUSIONS
The reproducibility was comparable to the reproducibility for acoustical stimulation in normal-hearing and hearing-impaired listeners. CLS data for electrical stimuli are preferably fitted with a model that is flexible in describing LGF shapes.
* Department of Clinical and Experimental Audiology, Academic Medical Center Amsterdam , Meibergdreef, Amsterdam , The Netherlands.
Femke L
FL
Theelen-van den Hoek
Monique
M
Boymans
Thomas
T
Stainsby
Wouter A
WA
Dreschler
D000162:Acoustics; D000368:Aged; D000369:Aged, 80 and over; D001309:Auditory Threshold; D016022:Case-Control Studies; D019929:Cochlear Implantation / Q000295:instrumentation; D003054:Cochlear Implants; D012048:Correction of Hearing Impairment / Q000295:instrumentation / Q000379:methods*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008144:Loudness Perception; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015588:Observer Variation; D019986:Persons with Hearing Disabilities / Q000523:psychology*; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted
Cochlear implant; categorical loudness scaling; loudness growth; loudness perception; reproducibility