Testing a Possible Cause of Reduced Ability of Children to Process Speech in Noise

Five to ten percent of school-age children in the United States are identified as having learning disability and 10 to 20% have attention deficit hyperactivity disorder (ADHD). Many of these children have difficulty with tasks that challenge the auditory system. It is estimated that 3 to 7 percent of children have difficulty with auditory processing as a major factor interfering with education (Chermak and Musiek, 1997). Pinpointing physiological causes of auditory processing difficulty has been elusive. Intervention is hampered by the lack of knowledge of possible physical causes and therefore intervention addresses systems rather than causes of auditory processing difficulty. Indeed, whether the problem has a peripheral or central origin is unclear. Identification of physiological differences in children with auditory processing disorders may lead to electrophysiologic identification of potential auditory processing disorders. Thus the possibility of early intervention might reduce the educational impact of this problem.

The aim of this study is to investigate the relationship of the efferent auditory neural system to the ability to process speech in noise. The study measures suppression of otoacoustic emissions in a population of adolescents with auditory processing difficulty as demonstrated by reduced ability to process speech in noise (Group A). These subjects will be compared to an age and sex matched group of adolescents with speech-in-noise test scores within normal limits (Group B). The study population will include 100 children between the ages of 12 and 18 years. All subjects must demonstrate normal puretone thresholds, speech recognition scores in quiet and middle ear function measured by acoustic immittance tests. Furthermore, the subjects' otoacoustic emissions must have reproducibility percentages within normal limits in the 2000, 3000, 4000 and 5000 Hz frequency bands. Subjects will complete an auditory speech recognition test battery (Scan-A and NU6 in multi-talker noise) and otoacoustic emission suppression tests. The auditory recognition tests each measure the subjects' ability to recognize speech in the presence of various types of noise and/or filtering. A group design will be used. Outcome parameters are the amount of suppression in dB for a group of subjects with normal speech understanding in noise and a group with reduced speech scores in noise and the relationship between speech measures and the degree of suppression.