Contents I. Introduction
The coronavirus disease 2019 (COVID-19) started in December 2019 and it has become a pandemic causing more than six million deaths across the globe [1], [2]. Face masks have been recommended by healthcare officials around the world as a precautionary measure to prevent the spread of this virus [3], [4]. It has been observed that there are different varieties of masks being used, and they have significantly different effects on speech intelligibility [5]. Face masks cause speech distortion and have a detrimental impact on speech perception, lowering the quality and intelligibility of speech [6], [7]. A comprehensive review of the impact of wearing a mask on speech production is reported in [8]. Considerable attenuation of signal strength at high frequencies between 2 and 16 kHz for all the mask designs is observed, resulting in an increased vocal effort, discomfort, and complications. The influence of masks on sound transmission in a lecture hall has been investigated in [9]. Male vocals are more affected by the use of masks than female voices. The signal has been lowered by 8–16 dB in the frequency range of 1.6–6.3 kHz. The use of face masks has raised the prevalence of vocal issues among healthcare workers [10]. Another research reveals that using surgical masks and face shields has an adverse impact on people with moderate to severe hearing loss [11]. Face masks have been observed to cause frequency-dependent transmission loss. When compared with testing without a mask, the directivity index deviates by up to 7 dB for frequencies over 3 kHz [12].
