Speech produced in noise: Relationship between listening difficulty and acoustic and durational parameters

Author(s): Simone Graetzer, Pasquale Bottalico and Eric Hunter


Speech produced in noise can be characterised by increases in intelligibility relative to conversational speech produced in quiet. The objectives of the study were to characterise the relationship between listening difficulty and speech produced in different noise and style conditions; and to evaluate the spectral and temporal modifications associated with these noise and style conditions. 19 subjects were instructed to speak at normal and loud volumes in the presence of fan-coil noise at 40.5 dBA and babble noise at 61 dBA. The speech signal was amplitude-normalised, combined with pink noise to obtain a signal-to-noise ratio of -6dB, and presented to 20 raters who judged their listening difficulty. Vowel duration, fundamental frequency (fo, in semitones) and fo modulation, and the proportion of the spectral energy in high relative to low frequency bands, increased with the level of the noise, independently of the effect of style. Listening difficulty was lowest when the speech was produced in the presence of high level noise and at a loud volume, indicating improved intelligibility. The difference in spectral energy was observed to predict listening difficulty, and therefore, intelligibility scores (IS). These findings have implications for the improvement of communication in noisy environments.