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Effects of different types of face coverings on speech acoustics and intelligibility
Abstract
This paper reports the results of two experiments investigating the effects on speech acoustics and intelligibility of a number of different types of forensically-relevant fabric mouth and face coverings, including the niqāb (full-face Muslim veil), balaclava, and surgical mask. For the perceptual (intelligibility) experiment, subjects were presented with two types of speech stimuli, 'bimodal' and 'unimodal', and asked to write down what they heard. Four facial guises were used (niqāb, balaclava, surgical mask, no covering). In the bimodal condition (video + audio), subjects saw and heard video recordings of actors reading target words embedded in a standardised carrier sentence. In the unimodal (audio only) condition, subjects heard just the soundtrack of the same video recordings, i.e., no visual image was present. It was found in the perceptual test that the subjects could in all four guise conditions correctly identify target words with a high degree of reliability, and that a small number of confusion types accounted for the majority of the errors. For the second (acoustic) experiment, the objective was to assess the sound transmission loss characteristics of the fabrics from which these and other face coverings are composed. This experiment showed that transmission loss was negligible for all but one of the fabrics, suggesting that speech intelligibility problems created when mouth and face coverings are worn by speakers must derive principally from the reduction in visual information available to listeners and/or from the auditory consequences of interference with speech articulation caused by the face coverings, rather than from transmission loss of the fabrics themselves.
... A subset of studies compared the effect of including or excluding visual information on auditory perception of talkers wearing masks. Overall, the outcomes of these studies support the additional influence of visual cues on auditory-perception of speech when masks are worn [24, 31, [33][34][35]. Of these, one study included audio recorded without a mask, but included audio-visual scenes in which the talker did or did not wear a mask [33]. ...
... The remaining studies comparing audio only and audio-visual conditions included audio recorded when the talkers actually were or were not wearing masks, and presented this audio to listeners with and without accompanying video [24,31,34]. These combined results studied audio-only and audio-visual consonant recognition for talkers donning eight distinct types of face concealment. ...
... The authors found that, overall, consonant identification accuracy in audio-visual conditions exceeded the audio-only condition, especially in the presence of background noise, and that this effect was stronger for some types of coverings over others. [34] found that while listener accuracy was lower in the audio-visual condition for three types of face coverings (niqab, surgical mask, balaclava), the overall number of consonant misperceptions was very small (2%). These confusions were driven by relatively few error types. ...
During the COVID-19 pandemic, personal protective equipment such as facial masks and coverings were mandated all over the globe to protect against the virus. Although the primary aim of wearing face masks is to protect against viral transmission, they pose a potential burden on communication. The purpose of this scoping review was to identify the state of the evidence of the effect of facial coverings on acoustic and perceptual speech outcomes. The scoping review followed the framework created by Arksey & O’Malley (2005) and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews guidelines (PRISMA-ScR; Tricco et al., 2018). The search was completed in May 2021 across the following databases: PubMed, EMBASE, PsycINFO, Web of Science, and Google Scholar. A total of 3,846 records were retrieved from the database search. Following the removal of duplicates, 3,479 remained for the title/abstract screen and 149 were selected for the full-text review. Of these, 52 were included in the final review and relevant data were extracted. The 52 articles included in the final review consisted of; 11 studied perceptual outcomes only, 16 studied acoustic outcomes only, and 14 studied both perceptual and acoustic outcomes. 13 of these investigated acoustic features that could be used for mask classification. Although the findings varied from article to article, many trends stood out. Many articles revealed that face masks act as a low pass filter, dampening sounds at higher frequencies; however, the frequency range and the degree of attenuation varied based on face mask type. All but five articles that reported on perceptual outcomes showed a common trend that wearing a face mask was associated with poorer speech intelligibility. The findings of the scoping review provided evidence that facial coverings negatively impacted speech intelligibility, which is likely due to a combination of auditory and visual cue degradation. Due to the continued prevalence of mask use, how facial coverings affect a wider variety of speaker populations, such as those with communication impairments, and strategies for overcoming communication challenges should be explored.
... Other studies focused on the perceptual effects of face coverings [6] [8]. For example, the impact of of niqāb, balaclava and a surgical mask was examined with regards to the perception of voicing, manner and place of articulation of stops [6]. ...
... Other studies focused on the perceptual effects of face coverings [6] [8]. For example, the impact of of niqāb, balaclava and a surgical mask was examined with regards to the perception of voicing, manner and place of articulation of stops [6]. Some subtle misperceptions were observed in place of articulation of fricatives (especially /f/ vs. /T/) and nasals (esp. ...
... /n/ and /N/), though overall, a surprisingly small number of misperceptions was attested. In contrast to the study of the isolated sound perception [6], the experiment in [8] examined listeners' transcriptions of whole words and sentences produced by speakers wearing different types of face masks (N95, surgical, cloth). The impact on intelligibility was found to be rather negligible and also comparable across all face masks (3-5%). ...
The current study aims at quantifying the effects of wearing a face mask on speech perception, by investigating performance of native English listeners in a phoneme monitoring task with monosyllabic words containing voiceless fricatives. Previous experimental work on the topic has mainly focussed on the effects of acoustic filtering caused by the use of face coverings with mixed results and weak effects of mask wearing on speech perception. In this experiment, we explore the interplay of acoustic filtering with other potentially relevant factors such as the presence of visual cues, lexical frequency and listener-specific background. We provide evidence that suggests the impact of face coverings (esp. FFP-2 face mask) on speech perception is not directly moderated by the acoustic properties of masked speech. Rather, it is inked to an interplay of audiovisual integration, the absence of visual cues for (some) target fricatives, and the listener-specific sociolinguistic background.
... Medical masks and cloth face masks obstruct visual cues that contribute to speech intelligibility. [25] A medical mask that has been given United States Food and Drug Administration approval typically has three layers: An outside and inner layer blue, nonwoven polypropylene, and a filtering material created using the "spun bond melt blown spun bond" technique in the middle. [26] Facial and respiratory PPE covering the mouth and nose have been reported to diminish speech intelligibility and impair the wearer's verbal communication ability by attenuating sound transmission and reducing intelligibility because of muffled speech and impingement on the nasal alae. ...
... Studies showed that masks obstruct visual cues, which contribute to speech intelligibility. [8,25,33,34] Wearing masks makes communication harder because masks muffle the sound, which makes it difficult to understand speech and takes away the ability to read lips, which may be the reason for poorer speech intelligibility, speech naturalness, and speech comprehensibility rating with medical mask compared to the ratings without medical mask. [35] Similarly, facial PPE and respiratory PPE covering the mouth and nose have been reported to diminish speech intelligibility and impair the wearer's verbal communication ability by attenuating sound transmission and reducing intelligibility because of muffled speech and impingement on the nasal alae. ...
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.
... In contrast, research findings on listeners' understanding of speakers either wearing or presented as wearing face coverings are more straightforward (Badh and Knowles 2023). In conditions without background noise, L1 English listeners understand L1 English speakers physically wearing surgical masks or face coverings such as balaclavas to the same degree as they understand speakers wearing no masks (Llamas et al. 2008;Toscano and Toscano 2021). In the few studies where speakers who recorded audio samples via medical masks were paired with images of the masked speakers (including L2 speakers), listeners often understood the speakers significantly better than non-masked speakers, likely due to greater attention paid to masked speech (Pycha et al. 2022;Smiljanic et al. 2021). ...
Previous research has shown that speakers’ visual appearance influences listeners’ perception of second language (L2) speech. In Québec, Canada, the context of this study, pandemic mask mandates and a provincial secularism law elicited strong societal reactions. We therefore examined how images of speakers wearing religious and nonreligious coverings such as medical masks and headscarves influenced the comprehensibility (listeners’ ease of understanding) and intelligibility of L2 French speech. Four L2 French women from first language (L1) Arabic backgrounds wore surgical masks while recording 40 sentences from a standardized French-language speech perception test. A total of 104 L1 French listeners transcribed and rated the comprehensibility of the sentences, paired with images of women in four visual conditions: uncovered face, medical mask, hijab (headscarf), and niqab (religious face covering). Listeners also completed a questionnaire on attitudes toward immigrants, cultural values, and secularism. Although intelligibility was high, sentences in the medical mask condition were significantly more intelligible and more comprehensible than those in the niqab condition. Several attitudinal measures showed weak correlations with intelligibility or comprehensibility in several visual conditions. The results suggest that listeners’ understanding of L2 sentences was negatively affected by images showing speakers’ religious affiliation, but more extensive follow-up studies are recommended.
... One commonly suggested design improvement is the introduction of transparent panels, which provide listeners with increased visual access to a talker's mouth and face (Atcherson et al., 2017;Corey et al., 2020;Cox et al., 2022;Tavanai et al., 2021;Thibodeau et al., 2021;Yi et al., 2023). The benefit of access to visual cues on performance in speech understanding tasks is well established, including evidence to support the benefit of transparency in face masks (Atcherson et al., 2017;Erber, 1969;Giovanelli et al., 2021;Llamas et al., 2008;Macleod & Summerfield, 1987;Sönnichsen et al., 2022;Sumby & Pollack, 1954;Thibodeau et al., 2021;Yi et al., 2021Yi et al., , 2023. In a speech recognition task, Thibodeau et al. (2021) presented participants with videos of a speaker wearing a mask containing a transparent window, and videos of the speaker wearing the same mask but with a piece of fabric covering the transparent section (blocking visual access to the speaker's mouth). ...
The use of face coverings can make communication more difficult by removing access to visual cues as well as affecting the physical transmission of speech sounds. This study aimed to assess the independent and combined contributions of visual and auditory cues to impaired communication when using face coverings. In an online task, 150 participants rated videos of natural conversation along three dimensions: (1) how much they could follow, (2) how much effort was required, and (3) the clarity of the speech. Visual and audio variables were independently manipulated in each video, so that the same video could be presented with or without a superimposed surgical-style mask, accompanied by one of four audio conditions (either unfiltered audio, or audio-filtered to simulate the attenuation associated with a surgical mask, an FFP3 mask, or a visor). Hypotheses and analyses were pre-registered. Both the audio and visual variables had a statistically significant negative impact across all three dimensions. Whether or not talkers’ faces were visible made the largest contribution to participants’ ratings. The study identifies a degree of attenuation whose negative effects can be overcome by the restoration of visual cues. The significant effects observed in this nominally low-demand task (speech in quiet) highlight the importance of the visual and audio cues in everyday life and that their consideration should be included in future face mask designs.
... The main passive effect among studies was induced filtering regarding wearing face masks. Acoustic analysis of speech signal [24,25] or speech recognition threshold evaluation [6], following face mask usage, showed decreased sound pressure levels in the range from 3 to 27 dB SPL [13,16]. Therefore, face mask usage as an effective factor in understanding speech signals has been considered. ...
Introduction: Using personal protective equipment, especially face masks, in the COVID-19 pandemic era may make verbal communication difficult. Furthermore, acoustic changes in mask-wearing conditions may affect speech audiometry results. This study investigates the effect of wearing a face mask on the word recognition score and the role of speech frequency content in this effect. Materials and Methods: This study was planned and conducted in two phases. In the first phase, the validity and reliability of two speech material lists, high-pitch and low-pitch, were determined. In the second phase, the word recognition score was measured for “mask-wearing” and “covering mouth without a mask.” Results: The statistical analysis showed that the content validity ratio was 0.92, and the content validity index was 0.8. Therefore, both speech lists were valid. For these lists, the mixed analysis of variance analysis showed that the scores for “mask-wearing” were significantly lower than “covering mouth without a mask,” and there was more reduction in scores for the high-pitched list (F=8.7, df=1, P<0.005). Conclusion: In terms of the impact of a face mask on speech, explaining how speech audiometry is performed, especially in monitoring treatments, may help limit the probability of misinterpretation of speech test findings. Furthermore, understanding the impact of face masks on word recognition scores in adopting sufficient auditory rehabilitation procedures is necessary.
... Before the COVID-19 pandemic, research focused on examining the acoustic effects of various fabrics for judicial purposes. [2] However, with the global spread of COVID-19, the use of PPE has become widespread, leading to observed effects on communication. For example, a study has reported voice radiation distortion, [3] and recent reports highlight communication challenges between health-care workers and patients due to the use of PPE. ...
Objectives
The transmission of severe acute respiratory syndrome coronavirus-2 occurs primarily through droplets, which highlights the importance of protecting the oral, nasal, and conjunctival mucosas using personal protective equipment (PPE). The use of PPE can lead to communication difficulties between healthcare workers and patients. This study aimed to investigate changes in the acoustic parameters of speech sounds when different types of PPE are used.
Methods
A cross-sectional study was conducted, enrolling 18 healthy male and female participants. They were instructed to produce a sustained [ɑː] vowel for at least 3 s to estimate voice quality. In addition, all Turkish vowels were produced for a minimum of 200 ms. Finally, three Turkish fricative consonants ([f], [s], and [ʃ]) were produced in a consonant/vowel/consonant format with different vowel contexts within a carrier sentence. Recordings were repeated under the following conditions: no PPE, surgical mask, N99 mask, face shield, surgical mask + face shield, and N99 mask + face shield. All recordings were subjected to analysis.
Results
Frequency perturbation parameters did not show significant differences. However, in males, all vowels except [u] in the first formant (F1), except [ɔ] and [u] in the second formant (F2), except [ɛ] and [ɔ] in the third formant (F3), and only [i] in the fourth formant (F4) were significant. In females, all vowels except [i] in F1, except [u] in F2, all vowels in F3, and except [u] and [ɯ] in F4 were significant. Spectral moment values exhibited significance in both groups.
Conclusion
The use of different types of PPE resulted in variations in speech acoustic features. These findings may be attributed to the filtering effects of PPE on specific frequencies and the potential chamber effect in front of the face. Understanding the impact of PPE on speech acoustics contributes to addressing communication challenges in healthcare settings.
... Further data analysis and future iterations of this study could consider specifically the identification of keywords involving fricatives and plosives. These segments tend to be commonly misperceived when produced with a face mask even in quiet [18]. The study could also benefit from additional auditory and acoustic analyses of the target sentence stimuli in terms of speaking style. ...
This paper examines the perception of speech produced with face masks in everyday multi-talker environments. Three groups of participants listened to English target sentences produced with or without a face mask in the presence of English or Lithuanian competing speech. Participants were monolingual English listeners, and second language English listeners with either Lithuanian or Mandarin Chinese as first language (L1). Lithuanian listeners also completed the experiment with Lithuanian target sentences. Participants were generally more accurate perceiving sentences produced without a face mask, and when listening in L1. Competing speech in a language matching the target lowered perception accuracy. Exceptionally, only when Lithuanian participants (with both English and Lithuanian knowledge) listened for Lithuanian targets was there no added challenge from matching language of target and competing speech. We conclude that acoustic distortions from face masks present an across-the-board difficulty while linguistic knowledge can reduce distraction from competing speech.
Face masks are recommended to minimize the spread of COVID-19 and are required in many health care settings. Although masks have documented health advantages, they also negatively impact communication, an essential element of clinical neuropsychological assessment. Using a large clinical data set from a major academic medical center, we investigated the effect of mask wearing on neuropsychological test performance. Specifically, we examined performance on eight standard, widely used neuropsychological tests between a prepandemic (unmasked) and postpandemic (masked) group, composed of 754 and 837 adult patients, respectively. We compared performance on verbally mediated versus visually mediated tests, hypothesizing that the postpandemic group, compared to the prepandemic group, would perform significantly lower on the verbally mediated tests but not on the visually mediated tests. In partial support of the hypothesis, we found that the postpandemic group performed significantly worse on the Auditory Verbal Learning Test (AVLT; p = .001). Secondary analyses showed that age moderated the mask-related effect (p = .038), whereby patients 65 and older had significantly worse performance on Digit Span (p = .0027) and the AVLT (p = .0002) with masks on, while patients younger than 65 showed no significant differences. There were no significant differences on any visually mediated tests. These findings suggest that mask wearing during neuropsychological assessment compromises performance on verbally mediated tests in older patients. These findings are particularly relevant for neuropsychologists practicing in geriatric settings. Neuropsychologists performing assessments with masks should be aware that masks may artificially deflate patient scores for reasons unrelated to cognition or clinical condition.
This article describes a study that emerged as a result of the severe acute respiratory syndrome crisis that struck Hong Kong in 2003. One outcome of the severe acute respiratory syndrome crisis was that all personnel in all educational institutions in Hong Kong were compelled to wear face masks for the period April–August 2003. Consequently, the English language oral test for the Grade 11 public examination (with a candidature of approximately 100,000) taken in June 2003 was conducted with all test takers and oral examiners wearing face masks.
The influence of the flow resistance of fabrics on their absorption characteristics has been investigated by measuring the flow resistance and the absorption characteristics. To deal with this subject from the point of view of the design and density of fabrics, we wove 13 different kinds of cotton fabrics as samples. The results obtained are as follows:(1) The relation between flow resistance Rf of fabrics and flow speed V can be given as follows: Rf=Ai+BiV where Ai and Bi are constants fixed by the design and density of a fabric. In a range of small densities, the value of Bi is nearly zero, while Ai and Bi increase together in value as the density of a fabric increases.(2) There are two types of absorbing mechanisms, the viscosity resistance type and the resonance type depending on the kinds of fabrics. A fabric is of the viscosity resistance type if its flow resistance depends only on air viscosity in a small range of flow speeds, namely, Rf=Ai.(3) A fabric is of the viscosity resistance type if it has an air space behind it, provided the relation among frequency f0, which shows the maximum absorption coefficient, depth d of the air space, and Rf can be given as follows: f0=(c/4-aRf)d-1 where c is the speed of a sound wave and a is a constant fixed by the design of the fabric. This empirical formula means that a fabric has the maximum absorption coefficient when it is placed at a shorter distance than the place where the particle velocity is a maximum.(4) The relation between maximum absorption coefficient α∞ and of Rf fabrics woven with the same design is: α∞=a'+a“ Rf where a' and a” are constants fixed by the design of the fabrics.
A comprehensive analysis of transfer-function measurement based on maximum-length sequences (MLS) is presented. MLS methods employ efficient cross correlation between input and output to recover the periodic impulse response (PIR) of the system being measured. In the face of external noise and nonlinearities, the MLS approach is shown to be as robust as time-delay spectrometry (TDS). Like TDS, MLS methods are also capable of rejecting or selecting nonlinear (distortion) components when measuring weakly nonlinear systems. An MLS coherence function is defined that is not unlike the coherence function usually associated with dual-channel FFT analyzers. Finally, a new low-cost instrument based on the IBM-PC makes MLS measurements generally available and affordable.