Speech Perception for Unilateral v. Bilateral Hearing Loss in Children

Question

I was reading an article regarding Unilateral Hearing Loss and came upon a study conducted by (Bess, Tharpe, & Gibler, 1986). This study went on to describe effects of unilateral hearing loss on speech perception and that those kids with severe-profound unilateral hearing loss exhibited poorer speech recognition when compared to those of mild-moderate unilateral hearing loss. My question is, has there been any study to compare the speech perception of a unilateral hearing loss to a bilateral hearing loss of the same degree and configuration? If so what were their findings? Was the bilateral worse than unilateral when comparing speech and localization? Thanks for your time.

Answer

To my knowledge, there has been no research directly comparing listeners with unilateral and bilateral hearing loss on tasks of speech perception and localization. However, based on what we know about the auditory cues required for localization (e.g., interaural time and intensity differences), it is reasonable to assume that those with unilateral hearing loss are more likely to experience localization difficulties than those with bilateral hearing loss in most situations. Furthermore, we know that, in general, the greater the degree of unilateral hearing loss, the poorer the localization and speech perception ability. But, there is great individual variability and we cannot easily predict the speech perception and localization abilities of an individual based on an audiogram.

In a recent study that addresses part of your question, Rothpletz, Tharpe, and Grantham (2004) examined the effects of asymmetrical signal degradation on binaural speech perception ability in normal hearing children and adults. Specifically, there were 3 listening conditions:

1. monaural, with mild degradation in 1 ear;
2. binaural, with mild degradation in both ears (symmetric degradation);
3. binaural, with mild degradation in one ear and severe degradation in the other ear (asymmetric degradation).

Sentences and babble were degraded digitally to simulate mild and severe cochlear hearing loss. All participants demonstrated significant binaural advantage (average of 7 dB) when listening to symmetrically degraded signals as compared to when listening monaurally. In contrast, adults and children achieved little or no binaural benefit, on average, when listening to asymmetrically degraded signals. Of course, this study used normal hearing listeners and individuals with hearing loss may perform quite differently both as a result of the loss itself and long term listening experience.

References

Rothpletz AM, Tharpe AM, & Grantham W (2004). "The Effect of Asymmetrical Signal Degradation on Binaural Speech Recognition". Journal of Speech, Hearing, Language Research.

Anne Marie Tharpe, Ph.D., has been an audiologist for over 20 years. She is on the faculty in the Department of Hearing and Speech Sciences at the Vanderbilt Bill Wilkerson Center for Otolaryngology and Communication Sciences in Nashville Tennessee. She can be contacted at anne.m.tharpe@vanderbilt.edu