Best Face Masks for Teachers
Comparison of the acoustic effects of face masks on speech
Face masks are an important tool for slowing the transmission of COVID 19, but they can make it more difficult to understand speech, especially for listeners with hearing loss. Face masks muffle high-frequency sounds that are critical for speech understanding and block visual cues that are especially important for people with hearing loss.
As schools resume in-person operation, it is important teachers consider which mask and face covering they are using in the classroom.
Earlier this year, an academic research study was done to compare the effects of different masks on speech signals. The results of the study show:
- Surgical masks and KN95 masks have the least impact on speech intelligibility. These masks do attenuate (block out) high frequency sounds however they had the least effect on acoustic attenuation.
- Transparent masks or face shields allow listeners to see lip movements and facial expressions however clear plastic attenuates (blocks) sound more strongly than material masks. The face shield caused especially strong distortion, even at low frequencies. Face shields attenuate sounds by as much as 13db. To put this into perspective we consider normal hearing levels for a child to be between 0 and 15dB. This means if a face shield attenuates sound up to 13dB, a child that was hearing within the normal range may not be able to hear their teacher adequately in class.
- The performance of cloth masks varies depending on the fabric used and the number of layers. Loosely woven fabrics, such as cotton and jersey, have the least effect on sound. Densely woven fabrics, such as denim and twill, block more sound.
So which face mask is best?
The choice of face mask depends on:
- acoustic performance
- visual transparency
- effectiveness against virus
The best choice overall is single-use surgical masks and KN95 respirators, which provide excellent acoustic performance and are designed to filter small particles. The next best solution would be a material mask comprised of three layers of t-shirt fabric. This is shown to provide as much protection as medical masks, and only 4 dB of high-frequency attenuation.
Where can I get more information?
If you’d like more information on this, or if you think you may be experiencing hearing loss, please contact us to book an appointment in Bedfordview or Benoni by calling our office on 011 615 3047 or email email@example.com
Information obtained from the Hearing Journal, January 2021