Auditory Signal Processing in a Hearing-Impaired Subject with Residual Ultra-Audiometric Hearing

A number of hearing-impaired individuals with near-normal thresholds for frequencies above 8 000 Hz who are characterized by good speech articulation have recently been identified. It is unclear whether this unusually good articulation is linked to the ability of such persons to process speech signals containing energy that falls within the range of their residual, high-frequency hearing (for example, certain consonants). This paper reports a detailed study of the signal-processing capabilities of one patient with a long-standing, severe to profound hearing loss in the standard audiometric range, and normal left-ear thresholds in the region of 13 000 Hz. Measures obtained include difference limens for frequency and intensity, gap detection, rate matching, temporal integration, and tone-on-tone masking profiles (psychoacoustical tuning curves). In addition, measures of speech production and perception were made when the patient was using an experimental hearing aid designed to transpose speech range frequencies into the region of her residual high-frequency hearing. Results indicate the patient can efficiently process signals which fall within the band of her best hearing, and suggest her ultra-audiometric hearing may be useful in speech communication.Nous avons etudie la capacite de traiter les signaux auditifs chez une patiente presentant une deterioration severe a profonde dans le champ conventionnel d'audibilite, et des seuils d'audition presque normaux pour des frequences aux environs de 13 000 Hz. Nous avons enregistre les seuils differentiels de frequence et d'intensite, la detection d'une interruption dans un signal, l'integration temporelle, les courbes d'accord psycho-acous-tique de Zwicker et Schorn, la capacite d'extraire l'information concernant le taux de repetition a partir de signaux de haute frequence spectrale. Nous avons aussi effectue des mesures de perception et de production de la parole lorsque la patiente utilisait une prothese experimentale transposant les frequences de la parole dans la region de 13 000 Hz.Les resultats indiquent que cette personne est capable de traiter les signaux aux environs de 13 000 Hz au moins aussi bien que ceux qui tombent dans la region de sa deterioration auditive, ce qui permet de penser qu'elle est en mesure d'utiliser le residu auditif ultra-audiometrique pour la communication parlee.