Combining degradations: The effect of background noise on intelligibility of disordered speech

The effect of background noise on intelligibility of disordered speech was assessed. Speech-shaped noise was mixed with neurologically healthy (control) and disordered (dysarthric) speech at a series of signal-to-noise ratios. In addition, bandpass filtered control and dysarthric speech conditions were assessed to determine the effect of noise on both naturally and artificially degraded speech. While significant effects of both the amount of noise and the type of speech were revealed, no interaction between the two factors was observed, in either the broadband or filtered testing conditions. Thus, it appears that there is no multiplicative effect of the presence of background noise on intelligibility of disordered speech relative to control speech. That is, the decrease in intelligibility due to increasing levels of noise is similar for both types of speech, and both types of testing conditions, and the function for dysarthric speech is simply shifted downward due to the inherent source degradations of the speech itself. Last, large-scale online crowdsourcing via Amazon Mechanical Turk was utilized to collect data for the current study. Findings and implications for this data and data collection approach are discussed.