Measures of spectral tilt

Abstract

Crude measures of spectral tilt (F0‐H2 difference, and F0‐F1 difference) have been demonstrated to be useful for distinguishing phonation types. However with such methods, it is difficult to control for differences due to variations in vowel quality and F0. In order to place such measures on a firmer foundation, the differences in vowel quality can be compensated for by inverse filtering. This technique has been used for analyzing vowels in languages having contrasting phonation types. FM recordings of airflow data in Burmese and Hmong, and ordinary AM audio recordings of !Xoo and Jalapa Mazatec were analyzed. AM recordings can be used, as phase distortion may be neglected while working in the frequency domain. FFT spectra were made of the inverse‐filtered waveforms. We considered several questions such as computational methods for deriving the amplitudes of harmonics, the expected dependency of amplitude on frequency, and the appropriate range of frequencies to examine. The results show that measures of spectral tilt obtained from inverse‐filtered data can be used to characterize differences in phonation type. [Work supported by NINCDS.]