The effect of frequency compression and high- frequency directionality on horizontal localisation and speech in noise recognition Ingrid Yeend, Anna O’Brien, Lisa Hartley, Gitte Keidser and Myriel Nyffeler* National Acoustic Laboratories *Phonak AG ASA meeting May 2010, Sydney

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Introduction What is frequency compression? Compression of a range of input frequencies into a smaller output range Permanent Source: Nyffeler, 2008

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Introduction What is high frequency directionality? Directionality applied to the high-frequencies that is designed to provide changes in spectral shape with azimuth Source: Phonak

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Objective To investigate the effect of frequency compression, high frequency directionality, and the combination of the two on horizontal localisation and speech recognition in noise.

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Method 23 experienced hearing aid users Naida V SP matched to NAL-NL1 targets (-3dB if 3FA < 60dB HL) 8 weeks FC On FC Off

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Method Objective tests: horizontal localisation (pink noise, cockatoos) speech recognition in noise Subjective tests: Speech, Spatial & Qualities of Hearing (SSQ) questionnaire exit interview

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Results – objective tests Horizontal localisation high frequency directionality reduced F-B RMS errors by average 4.5 ̊ x no significant effect of time x no significant interactions involving frequency compression, microphone mode or time.

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Results – objective tests Speech recognition in noise high frequency directionality provided spatial release from masking X no other significant interactions

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Results – subjective feedback high degree participant satisfaction with device X no significant difference on SSQ for FC on vs FC off. X no significant interaction between FC and microphone mode on exit interview

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Conclusions Horizontal localisation - front-back localisation cues less useable because spectrally compressed - mid-frequency (~ kHz) information may have replaced high frequency cues Speech recognition in noise - excessive or insufficient audibility - speech test too difficult - NAL-NL1 gives < HF gain than prescription methods used in some other research and may have affected audibility

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Clinical Implications and future research Clinical implications - FC neither harms nor helps front-back discrimination, speech recognition in noise or satisfaction with amplification - choose high frequency directionality where possible Future research - Effect of prescribed gain? - Is cognitive loading in challenging listening situations eased by FC? - Longer adaptation period (adults)?

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Acknowledgements from the National Acoustic Laboratories Harvey Dillon, Dan Zhou from Phonak AG Ora Buerkli, Cleon Davey, Stefan Launer from University of Melbourne Hugh McDermott

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Method Appointment Overview AppointmentData collected 1 (0 weeks)Initial appointment, unaided localisation 2 (+ 2 weeks)Fitting test devices 3 (+ 1 week)Fine tuning, localisation and speech testing 4 (+ 3 weeks)Localisation and speech testing 5 (+4 weeks)Localisation and speech testing, enable/disable FC, SSQ, scheme exit interview 6 (+ 1 week)Fine tuning, localisation and speech testing 7 (+ 3 weeks)Localisation and speech testing, MMSE 8 (+ 4 weeks)Localisation and speech testing, SSQ, scheme exit interview

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Prescribed vs actual Frequency Compression Threshold

National Acoustic Laboratories, Sydney, Australia ASA 2010, Sydney Average audiometric thresholds