Talkers produce more pronounced amplitude modulations when speaking in noise

Abstract

Speakers adjust their voice when talking in noise (known as Lombard speech), facilitating speech comprehension. Recent neurobiological models of speech perception emphasize the role of amplitude modulations in speech-in-noise comprehension, helping neural oscillators to “track” the attended speech. This study tested whether talkers produce more pronounced amplitude modulations in noise. Across four different corpora, modulation spectra showed greater power in amplitude modulations below 4 Hz in Lombard speech compared to matching plain speech. This suggests that noise-induced speech contains more pronounced amplitude modulations, potentially helping the listening brain to entrain to the attended talker, aiding comprehension.

Enhanced amplitude modulations contribute to the Lombard intelligibility benefit: Evidence from the Nijmegen Corpus of Lombard Speech

“…Using modulation spectra, they observed more pronounced amplitude modulations in the temporal envelope of Lombard speech compared to plain speech, as evidenced by greater power in the lower frequency range of the modulation spectra, across a collection of four different speech corpora. However, only production data were reported in the study by Bosker and Cooke (2018). As such, the contribution of this greater power in the modulation domain in Lombard speech to speech intelligibility in noise remains unknown.…”

“…Based on these neurobiological models, Bosker and Cooke (2018) assessed whether speakers, potentially in an attempt to aid speech intelligibility, would also naturally produce more enhanced amplitude modulations when talking in a noisy acoustic environment. Using modulation spectra, they observed more pronounced amplitude modulations in the temporal envelope of Lombard speech compared to plain speech, as evidenced by greater power in the lower frequency range of the modulation spectra, across a collection of four different speech corpora.…”

“…As such, the contribution of this greater power in the modulation domain in Lombard speech to speech intelligibility in noise remains unknown. Furthermore, only English corpora were analyzed in Bosker and Cooke (2018); thus, further cross-linguistic validation is called for.…”

“…Native speakers of Dutch were recorded producing Lombard sentences (produced while speech-shaped noise was presented over headphones) and matching plain speech sentences (the same sentences produced in quiet). Adopting the methods of Bosker and Cooke (2018), we expected to find greater power in the modulation spectrum of Dutch Lombard speech (vs. plain speech), indicative of more pronounced amplitude modulations.…”

Linguistic structure and meaning organize neural oscillations into a content-specific hierarchy

“…For each stimulus, we computed the wideband speech envelope at a sampling rate of 150 Hz following the procedure reported by Keitel et al (2018) and others (e.g., Bosker & Cooke, 2018;Gross et al, 2013;Keitel et al, 2017). We first filtered the acoustic waveforms into 8 frequency bands (100-8,000 Hz; third-order Butterworth filter, forward and reverse), equidistant on the cochlear frequency map (Smith, Delgutte, & Oxenham, 2002).…”