Effects of Spectral Slope on Perceived Breathiness in Vowels

of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Arts EFFECTS OF SPECTRAL SLOPE ON PERCEIVED BREATHINESS IN VOWELS By Mario Alberto Landera August 2006 Chair: Rahul Shrivastav Major Department: Communication Sciences and Disorders Previous studies have indicated that breathiness is correlated with measures of perturbation, aspiration noise, signal-to-noise ratio, first harmonic amplitude, and spectral slope. However, the role of spectral slope on perceived breathiness remains unclear. In a recent study, it was observed that varying spectral slope resulted in minimal changes on the perceived breathiness for synthetic vowels. However, the stimuli tested in this experiment included a relatively narrow range of spectral slope variation. The goal of the present experiment was to verify the role of spectral slope changes on the perception of breathiness by testing stimuli that had a wider range of variation in spectral slope and a constant signal-to-noise ratio. Ten voices (5 male and 5 female) representing various levels of breathiness were synthesized using a Klatt-synthesizer. Each of these voices was manipulated to generate two continua varying in their spectral slope from -3 dB/octave to -30 dB/octave. One continuum (CC series) had a constant cutoff frequency of 500 Hz, while the other continuum (VC series) had a cutoff frequency between the second harmonic (H2) and the third harmonic (H3). Ten listeners judged the degree of