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Abstract
Objective: To evaluate the auditory brainstem response (ABR) amplitudes evoked by tone pip and narrowband chirp (NB CE-Chirp) stimuli when testing post-screening newborns and to determine the difference in estimated hearing level correction values. Design: Tests were performed with tone pips and NB CE-Chirps at 4 kHz or 1 kHz. The response amplitude, response quality (Fmp), and residual noise were compared for both stimuli. Study sample: Thirty babies (42 ears) who passed our ABR discharge criterion at 4 kHz following referral from their newborn hearing screen. Results: Overall, NB CE-Chirp responses were 64% larger than the tone pip responses, closer to those evoked by clicks. Fmp was significantly higher for NB CE-Chirps. Conclusion: It is anticipated that there could be significant reductions in test time for the same signal to noise ratio by using NB CE-Chirps when testing newborns. This effect may vary in practice and is likely to be most beneficial for babies with low amplitude ABR responses. We propose that the ABR nHL threshold to eHL correction for NB CE-Chirps should be approximately 5 dB less than the corrections for tone pips at 4 and 1 kHz.
Notes
Acknowledgements
A preliminary version of this work was presented as a poster, ‘Do frequency specific chirps offer a quicker ABR assessment in newborns compared to tone pips?’, at the International Conference on Newborn Hearing Screening, Cernobbio (Lake Como), Italy, June 2012, and at the British Academy of Audiology Annual Conference, Manchester, UK, November 2012. The authors would like to thank Sungtak Hong, PhD student, Department of Marketing, London Business School, for performing the main statistical analysis of this study.
Declaration of interest: The authors alone are responsible for the content and writing of this paper. One of the authors (IF) received assistance to attend the NHS 2012 conference, referenced above, from Interacoustics UK. There were no further conflicts of interest.
Notes
1. The corrected age is the difference between the chronological and gestational age of the baby.
2. When using TDH-39 earphones, 30 dBeHL corresponds to 40 dBnHL. When using ER-3A inserts, 30 dBeHL corresponds to 30 dBnHL. The dBeHL to dBnHL correction includes two elements: an age-related transducer correction, and a correction to predict the behavioural threshold from the ABR threshold. Full details are given in the English Newborn Hearing Screening Programme guidelines for early audiological assessment (2011).