Current steering and results from novel speech coding strategies

• Published in: Otology & neurotology Vol. 29; no. 2; p. 203
• Main Authors: Buechner, Andreas, Brendel, Martina, Krüeger, Beate, Frohne-Büchner, Carolin, Nogueira, Waldo, Edler, Bernd, Lenarz, Thomas
• Format: Journal Article
• Language: English
• Published: United States 01.02.2008
• Subjects: Adult; Algorithms; Cochlear Implants; Cross-Over Studies; Deafness - psychology; Deafness - therapy; Electrodes, Implanted; Female; Fourier Analysis; Humans; Male; Middle Aged; Models, Statistical; Pitch Perception; Prospective Studies; Prosthesis Design; Speech Perception - physiology
• ISSN: 1531-7129
• DOI: 10.1097/mao.0b013e318163746

Advanced Bionics' cochlear implants have independent current sources that can share stimulation current between 2 contacts (Current Steering). By stimulating 2 adjacent electrodes with different weights, different pitches can be evoked, allowing to increase the number of processing channels. A counterbalanced crossover design was used to compare 3 different current steering implementations to the clinical HiRes strategy. The study was a prospective, within-subject, repeated-measure experiment. The study group consisted of 8 postlingually deaf subjects with a minimum of 12-month experience in HiRes. The following programs were evaluated: 1) a Fast Fourier Transformation (FFT)-based current steering implementation with 120 stimulation sites; 2) the same current steering implementation but with 16,000 stimulation sites; and 3) a current steering implementation based on a sinusoidal decomposition of the original signal with 16,000 stimulation sites. Speech perception tests in quiet and in Comité Consultatif International Télégraphique et Téléphonique (CCITT) noise, as well as with competing talker; an adaptive test of the frequency difference limen; a Quality Assessment Questionnaire. Current results do not show any improvement in speech perception for a certain current steering strategy compared with HiRes. However, when selecting the optimal current steering strategy, subjects could achieve a significant benefit compared with the clinical HiRes. In addition, the frequency difference limen could be reduced significantly at 1,280 Hz. Current steering seems to have the potential to improve both understanding in adverse listening situations and frequency resolution. However, the optimal implementation needs further investigation.