The impact of noise on speech comprehension
Backed by EU funding, the project SPIN (Natural speech comprehension: Comprehension of speech in noise) explored our capacity to understand speech by relying on the interaction between auditory processing and the specialised cognitive processes involved in speech comprehension and degraded speech restoration. Prior to the launch of this project, speech comprehension has mostly been studied in quiet environments. In real-world situations, speech sounds always occur with a certain amount of background noise, which further complicates the listening task. The work was original in that it considered the 'natural' manner of perceiving speech and approached its investigation through language-based as well as auditory-driven perspectives. The interdisciplinary team conducted experimental studies that included behavioural assessment, electrophysiological measurements and neuroimaging. Target populations were normal hearing participants, hearing-impaired patients and speech processing-impaired patients. Focusing on inter-individual variability observed in speech comprehension performance, researchers sought to unravel the links between sensory processes and speech intelligibility. Work resulted in a scale of phoneme resistance to noise, where high-energy sibilants are the more resistant speech sounds and low energy fricatives are the less resistant. Another line of research found that known languages are the most harmful background noise, and that different unknown languages produce masking effects. One critical finding, suggesting that neural resources are shared between listening and understanding, shows how noise is deleterious and can affect higher levels of cognition in short and long terms. Research on specific populations with language impairment (e.g. dyslexics) demonstrated that adult dyslexics were able to rely on de-noising strategies based on spatial unmasking. SPIN developed new methodologies to study and further understand the links between language capacities and speech-in-noise processing. For example, an adult screening was established that disentangles speech processing and auditory capacities as much as possible. Additionally, the team progressed with developing auditory classification images to better explore the auditory primitives used during speech perception. This renewed experimental method could fill a paradigmatic gap in speech research. Considering the increasing levels and varieties of noise in modern societies, project outcomes have important implications for understanding the neurocognitive processes underlying speech comprehension in general.
Keywords
Noise, speech comprehension, auditory processing, background noise, speech processing