Speech Intelligibility and Speech Naturalness while Speaking with and without Medical Mask

Abstract

Introduction: The COVID-19 situation has led to an increase use of medical mask for protection. Facial and respiratory PPE covering the mouth and nose have been reported to diminish Speech Intelligibility. Altering the volume, rate and volume and rate together may contribute to influencing the speech intelligibility and speech naturalness rating. Therefore, identifying the appropriate method to speak with medical mask can help train people to communicate with mask. This study aimed to (1) analyse effects of wearing masks on speech intelligibility, naturalness and comprehensibility, and (2) document an altered style of speaking to improve speech intelligibility, naturalness and comprehensibility while wearing masks. Method: Cross-over study design was used. Spoken utterances from 14 naïve speakers were recorded with and without medical mask, and speech in typical style, increased volume (loudness), reduced rate, and mixed method (combination of increased loudness and reduced rate) with medical mask was recorded from 12 professional speakers. Two expert listeners rated the naïve speakers, and two naïve listeners rated professional speakers using standard rating scales of speech intelligibility and naturalness. Percentage of correct identification of utterance was calculated as a measure of comprehensibility. Wilcoxon signed rank test and Friedman test were used to report significant differences among conditions and parameters analysed. Results: Speech intelligibility, naturalness and comprehensibility was poorer while speaking with medical mask than without them. Speaking in mixed method (combination of increased loudness and reduced rate), while using medical masks was the most appropriate style of speech in order to be intelligible, natural and comprehensible, followed by increased loudness style, typical style and reduced rate style. Conclusion: People should be alerted that wearing mask leads to reduction in speech intelligibility, comprehensibility and naturalness. These can be improved by modifying the style of speaking.