Effect of glottal dynamics in the production of shouted speech

In this paper characteristics of speech produced at different loudness levels are analyzed in terms of changes in the glottal excitation. Four loudness levels are considered in this study, namely, soft, normal, loud, and shout. The distinct changes in the excitation of the shout signal are analyzed using electroglottograph signals. The open and closed phases of the glottal vibration are distinctly different for shout signals, in comparison with those for normal speech. It is generally difficult to derive the glottal pulse information from the speech signal due to limitations in inverse filtering. Hence, the effects of changes in the excitation are examined by analyzing the speech signal using methods that can capture the temporal variations of the spectral features. In particular, the recently proposed methods of zero-frequency filtering and zero-time liftering are used in this analysis. It is shown that the closed phase behavior of the excitation at different loudness levels can be seen in the temporal variation of spectral energy in the low frequency (LF) (<400 Hz) region. The ratio of the LF to high frequency energy clearly discriminates the speech produced at different loudness levels. These distinctions in the excitation features are also observed in different vowel contexts and across several speakers.