An Investigation Into Incorporating Visual Information in Audio Processing.

The number of persons with hearing and vision loss is on the rise as lifespans increase. Vision plays an important role in communication, especially in the presence of background noise or for persons with hearing loss. However, persons with vision loss cannot make use of this extra modality to overcome their hearing deficits. We propose automatically utilizing some visual information in hearing aids through the addition of a small wearable camera. Our initial results show potentially significant benefits to incorporating low level robust visual cues when the background noise is high. This technique can potentially benefit all persons with hearing loss, with substantial improvements possible for the speech perception performance of persons with dual sensory loss.

Cross-modal extinction in a boy with severely autistic behaviour and high verbal intelligence.

Anecdotal reports from individuals with autism suggest a loss of awareness to stimuli from one modality in the presence of stimuli from another. Here we document such a case in a detailed study of A.M., a 13-year-old boy with autism in whom significant autistic behaviours are combined with an uneven IQ profile of superior verbal and low performance abilities. Although A.M.'s speech is often unintelligible, and his behaviour is dominated by motor stereotypies and impulsivity, he can communicate by typing or pointing independently within a letter board. A series of experiments using simple and highly salient visual, auditory, and tactile stimuli demonstrated a hierarchy of cross-modal extinction, in which auditory information extinguished other modalities at various levels of processing. A.M. also showed deficits in shifting and sustaining attention. These results provide evidence for monochannel perception in autism and suggest a general pattern of winner-takes-all processing in which a stronger stimulus-driven representation dominates behaviour, extinguishing weaker representations.

Effect of dual sensory loss on auditory localization: implications for intervention.

Our sensory systems are remarkable in several respects. They are extremely sensitive, they each perform more than one function, and they interact in a complementary way, thereby providing a high degree of redundancy that is particularly helpful should one or more sensory systems be impaired. In this article, the problem of dual hearing and vision loss is addressed. A brief description is provided on the use of auditory cues in vision loss, the use of visual cues in hearing loss, and the additional difficulties encountered when both sensory systems are impaired. A major focus of this article is the use of sound localization by normal hearing, hearing impaired, and blind individuals and the special problem of sound localization in people with dual sensory loss.

Acclimatization in wide dynamic range multichannel compression and linear amplification hearing aids.

Acclimatization was studied in hearing-impaired patients with no previous hearing aid (HA) experience who were fit bilaterally with either wide dynamic range multichannel compression (WDRMCC) or linear amplification (LA) HAs. Throughout 40 weeks of normal HA use, we monitored changes in nonsense syllable perception in speech-spectrum noise. Syllable recognition for WDRMCC users improved by 4.6% over the first 8 weeks, but the 2.2% improvement for LA users was complete in 2 to 4 weeks. Consonant confusion analyses indicated that WDRMCC experience facilitated consonant identification, while LA users primarily changed their response biases. Furthermore, WDRMCC users showed greater improvement for aided than unaided stimuli, while LA users did not. These results demonstrate acclimatization in new users of WDRMCC HAs but not in new users of LA HAs. A switch in amplification type after 32 weeks produced minimal performance change. Thus, acclimatization depended on the type of amplification and the previous amplification experience.

Bilateral amplification and sound localization: then and now.

This article is concerned with the evolution and pros and cons of bilateral amplification. Determining whether a bilateral hearing aid fitting is superior to that of a monaural hearing aid is a long-standing question; for this reason, the trend toward bilateral amplification has been slow. However, it is now assumed that bilateral amplification has significant advantages over monaural amplification in most cases, a view that is supported by our localization results. In this article, we will address the advantages of bilateral hearing aids and reveal some new localization data that show that most listeners with bilateral amplification, when tested unaided, as well as normal-hearing listeners manifested very high degrees of symmetry in their judgments of perceived angle while listeners who routinely use monaural amplification and those with asymmetric hearing loss had relatively large asymmetries. These data show that asymmetry in localization judgments is a much more sensitive indicator of abnormal localization ability than the magnitude of localization errors.

Lateralization of narrow-band noise by blind and sighted listeners.

The effects of varying interaural time delay (ITD) and interaural intensity difference (IID) were measured in normal-hearing sighted and congenitally blind subjects as a function of eleven frequencies and at sound pressure levels of 70 and 90 dB, and at a sensation level of 25 dB (sensation level refers to the pressure level of the sound above its threshold for the individual subject). Using an 'acoustic' pointing paradigm, the subject varied the IID of a 500 Hz narrow-band (100 Hz) noise (the 'pointer') to coincide with the apparent lateral position of a 'target' ITD stimulus. ITDs of 0, +/-200, and +/-400 micros were obtained through total waveform delays of narrow-band noise, including envelope and fine structure. For both groups, the results of this experiment confirm the traditional view of binaural hearing for like stimuli: non-zero ITDs produce little perceived lateral displacement away from 0 IID at frequencies above 1250 Hz. To the extent that greater magnitude of lateralization for a given ITD, presentation level, and center frequency can be equated with superior localization abilities, blind listeners appear at least comparable and even somewhat better than sighted subjects, especially when attending to signals in the periphery. The present findings suggest that blind listeners are fully able to utilize the cues for spatial hearing, and that vision is not a mandatory prerequisite for the calibration of human spatial hearing.