The role of contour shape in the perception of pitch height – new data Rachael-Anne Knight

1. The role of contour shape in the perception of pitch height – new data Rachael-Anne Knight knight@city.ac.uk • 7. Results • Both frequency and the combination of accents was significant. • Experiment a • Frequency F(3,15)=4.833,p<0.05 • Combination F(8,4)=6.33,p<0.01 • Experiment b • Frequency F(3,15)=4.362,p<0.05 • Combination F(8,4)=5.498,p<0.00 1. Background Evidence from production studies shows intonational plateaux associated with nuclear falls in SBS English1. This would not be predicted in an Autosegmental Metrical (AM) approach to intonational analysis, where contours are modelled as sequences of high and low turning points joined by interpolations. • 4. Subjects • Six naïve listeners participated in each experiment. • Experiment A: 5 males and 1 female, aged 19-50 (mean=30) • Experiment B: 5 females and 1 male, aged 29-55 (mean =37) • Mix of musical abilities in each group. Subjects were monolingual English speakers with no history of speech or hearing difficulties. 5. Task Subjects heard pairs of stimuli in which only the shape, but never the frequency of the two ‘Manny’ accents differed. Each combination of shapes was heard once.They chose in which member of each pair ‘Manny’ sounded higher in pitch. They listened through headphones in a a) sound treated booth b) quiet room and indicated their response via a computer keyboard. An example of an intonational plateau 2. Hypothesis & Research Question It is not clear why speakers produce plateaux but it is hypothesized that a plateau may make an accent sound higher in pitch. Therefore the research question is ‘Does a plateau sound higher than a peak of the same maximum frequency?’ 8. Discussion Accent shape has an effect on perceived pitch height in each experiment. In general an accent containing a longer plateau sounds higher than one containing a shorter plateau or peak. There is a likely effect of ‘stability sensitive weighting’2 whereby steady portions of the signal contribute more towards pitch perception. This type of difference in accent shape would not be captured by AM models of intonation but these results suggest that the distinction is perceptually relevant and perhaps should be included in models of intonation. Frequency also has an effect. A higher frequency causes the second accent to sound higher when the rise duration is controlled (a), but causes the first accent to sound higher when rise slope is controlled (b). 9. References 1. KNIGHT & NOLAN (2006) JIPA 36,1, 1-18 2. GOCKEL et al. (2001) JASA 109,2,701-712 3. Stimuli The utterance ‘Anna came with Manny’ (mostly voiced and sonorant) was recorded by a female phonetician. The portion ‘…came with Manny’ was extracted and the contour on ‘Manny’ was resynthesized : Maximum frequency: 160, 180, 200 or 210 Hz Shape: Peak, 50ms plateau, or 100ms plateau • 6. Statistics • Subject responses were coded as ‘1’ if the ‘Manny’ in the first utterance was chosen as sounding higher in pitch, and ‘2’ if the second ‘Manny’ was chosen (so a mean response closer to 1 shows more responses for the first stimulus). • This coding was entered as a dependent variable into two separate univariate MANOVAs. • Independent variables of : • Frequency (4): 160, 180, 200, 210 • Combination (9): • Peak and Peak • 50ms and 50ms • 100ms and 100ms • Peak and 50ms • 50ms and peak • Peak and 100ms • 100ms and Peak • 50ms and 100ms • 100ms and 50ms 3a. Two types of shape manipulation There are many different ways of creating a plateau in resynthesis. Here two are used and the results compared. Experiment a: rise starts from same point, gradient is different for different shapes. Experiment b: gradient is same for different shapes, rise starts earlier for longer plateaux Exp a. Exp b. Schematic diagram of contour types. Yellow = peak, Red = 50ms plat., White = 100ms plat.