This paper examines the Lombard effect on the excitation features in speech production. These features correspond mostly to the acoustic features at subsegmental (< pitch period) level. The instantaneous fundamental frequency F0 (i.e., pitch), the strength of excitation at the instants of significant excitation and a loudness measure reflecting the sharpness of the impulse-like excitation around epochs are used to represent the excitation features at the subsegmental level. The Lombard effect influences the pitch and the loudness. The extent of Lombard effect on speech depends on the nature and level (or intensity) of the external feedback that causes the Lombard effect.
Bibliographic reference. Bapineedu, G. / Avinash, B. / Gangashetty, Suryakanth V. / Yegnanarayana, B. (2009): "Analysis of Lombard speech using excitation source information", In INTERSPEECH-2009, 1091-1094.