Speech-language therapy students' auditory-perceptual judgements of simulated concurrent hypernasality and articulation disorders

Auditory-perceptual judgements are regarded as the standard method for assessing speech disorders. However, the results of auditory-perceptual evaluations and rater reliability can be affected by various factors, such as concurrent problems in multiple speech subsystems. This study investigated the effect of a co-occurring articulation disorder on auditory-perceptual judgements of hypernasality and the effect of co-occurring hypernasality on judgements of an articulation disorder. The speech stimuli were sentences produced by a male speaker who simulated four levels of hypernasality (typical nasality, and mild, moderate, and severe hypernasality) at four levels of disordered articulation (typical articulation, and mild, moderate, and severe articulation disorder). Thirty speech and language therapy students used visual analogue scales to rate the severity of hypernasality and articulation disorder for each speech sample. Results showed that the hypernasality ratings were significantly higher when articulation disorder co-occurred compared to those without. However, there was no significant difference between mild, moderate and severe concurrent articulation disorder on hypernasality ratings. The speech samples with typical articulation and those with severe articulation disorder were rated as more severe in terms of articulation problem when combined with severe hypernasality. However, there was no significant hypernasality effect on articulation ratings for speech with mild or moderate articulation disorder. The present results generally agreed with previous findings regarding the effect of co-occurring speech problems on auditory-perceptual judgements. Clinicians are advised to be cautious of the potential impact. If possible, speech evaluation using instrumental techniques should be used to supplement auditory-perceptual judgements.