Listeners' judgments of intelligibility of normal and Lombard speech

Abstract

Noise is one of the factors that influence speech intelligibility. The listening conditions, the context, the speaker, or the listener can also affect speech intelligibility. In presence of noise, speech is masked and its production is modified by what is called the Lombard reflex. The purpose of this work is to study the influence of psychoacoustic and psycholinguistic factors on speech produced in noise (Lombard speech) and normal speech. Through a series of perceptual tests the influence of the following factors on the judgments of intelligibility of normal and Lombard speech is investigated: (1) nature of the vocabulary; (2) size of the vocabulary; (3) sex of the speakers; (4) speech quality evaluation measure (global and segmental signal‐to‐noise ratio); (5) type of noise (white Gaussian noise and unintelligible speech (babble noise)]; and (6) ability of the listener to perform the task. A 49‐work database (alphanumeric plus control words produced by ten speakers) was used, for which some subsets can be classified as similar or not acoustically. The main conclusions of this work are the following. (1) The type of noise is an important factor that influences the intelligibility. Babble noise decreases the intelligibility compared to white Gaussian noise. (2) When additive babble noise is used, Lombard speech is more intelligible than normal speech. (3) When additive white noise is used, Lombard speech was found to be less intelligible than normal speech for the E‐SET vocabulary. Results about the influence of the different factors on the intelligibility of normal and Lombard speech will be presented and discussed.