I am currently working with Dr. Shafer to finalize the study that I will be focusing on for this program. The study focuses on examining speech processing in the auditory context of competing background noise influenced by language background experiences. More specifically, we’ll be observing performance differences between bilinguals and monolinguals in a task that requires discrimination of stimulus that is varied by voice pitch differences and “accents”. The stimulus used for this study includes both male and female voices, both of which vary in pith.
A pilot participant was tested and their results raised some interesting questions. The participant, an English monolingual, had no difficulty discriminating the target stimuli when the stimuli were male and female voices, but had greater difficulty discriminating the target stimuli and non-target stimuli were both female voices. When we compared the fundamental frequencies between the male-female voices there was a greater difference than when we compared the female-female voices. This leads us to believe the pitch in the stimuli used could have affected the degree of discrimination.
The fundamental frequency in voices are affected by numerous factors, two of them being hormonal levels and vocal fold thickness. Increase in testosterone and dehydrotestosterone in males causes an increase in bulk of laryngeal muscles and ligaments which leads to a drop in the higher octaves in pitch and voice crackling. Sound familiar? that is because this occurs primarily, but not exclusively, during puberty. Because of the low levels of testosterone in women and their estrogen levels, the female voice has a higher pitch than men because the higher octaves are preserved (K.V.S Kumar H. et.al.,). The increase in bulk in the male laryngeal muscles results in thicker vocal folds. Theses factors could have affected the degree of discrimination across the stimuli.
I would like to see if these results remain consistent when we recruit more participants. For this study we will also be recruiting participants with Auditory Processing Disorder, so It will be interesting to see if they respond to the female-female stimuli the same way the pilot participant did.