Silvia Murgia, PhD Student:

  1. Speech intelligibility in classrooms: which masks should we wear? : All children need good, clear instructional signals in low background noise for the best opportunity to understand the material being taught. A classroom’s shape, surroundings, and even its furnishings change how sound ‘sounds’ and speech is ‘heard’ in the classroom. The study of classroom acoustics is perhaps one of the most important, but often least considered, factors when considering the design of a classroom. The current pandemic situation will obligate teachers and students to wear protective masks. Together with poor classroom design, this will decrease the quality of the speech produced, consequently reducing speech intelligibility in classrooms. The purpose of this project is to determine which type of masks that teachers wear have the least impact on speech intelligibility to minimize the decrease in students’ speech intelligibility. Using this information, pragmatic guidelines can be put into place to give children the best opportunity for academic success, even in this complex pandemic situation.
  2. Intelligibility of dysphonic speech in auralized classrooms: Voice disorders reduces speech intelligibility. This study evaluated the effect of noise, voice disorders and room acoustics on vowel intelligibility. Twenty-nine college students listened to 11 vowels in /h/-V-/d/ format. The speech was recorded by three adult females with dysphonia and three adult females with normal voice quality. The recordings were convolved with two oral-binaural impulse responses with 0.4 s and 3.1 s of reverberation time. The intelligibility and the listening easiness were significantly higher in quiet condition, when the speakers had normal voice quality and in low reverberated environments, while the response time of the listener was longer in noise condition.

Tomás Sierra, PhD Student:

  1. Voice Intensity Changes in Artificial Acoustics: The regulation of speech level is primarily affected by the physiological features of the speaker such as vocal tract size and lung capacity; however, the auditory feedback plays a fundamental role in voice production. The current study examined the effects of room acoustics in an artificial setting on voice production in terms of sound pressure level and the relationship with the perceived vocal comfort and control. Three independent room acoustic parameters were considered: reverberation time, gain (alteration of the sidetone), and background noise. An increase in the sidetone led to a decrease in vocal intensity, thus increasing vocal comfort and vocal control. This effect was consistent in different reverberation times considered. Mid-range reverberation times (T30≈1.3 seconds) led to a decrease in the vocal intensity along with an increase on vocal comfort and vocal control. The presence of noise amplified the aforementioned effects for the variables analyzed.
  2. The Effect of Room Acoustics on Voice Parameters: A Systematic Review: The purpose of this study was to quantify the relationships between voice parameters and room acoustics. A comprehensive literature search was conducted using PubMed/MEDLINE, Science Direct, and Scopus. Several terms regarding self-reported vocal parameters (vocal fatigue, vocal effort, vocal load, and vocal comfort), as well as possible variants, were included in the search. Also, we included different terms related to room acoustic parameters, such as reverberation time, noise conditions, decay times, room sizes, among others. Finally, a focus group of four experts in the field (current authors) worked together to make conceptual connections and quantify the proposed relationship. In total, 26 publications met the criteria for inclusion. The occurrence and frequency of the most common parameters in the literature are presented, and a quantitative summary of their relationships are reported. The most common journals and proceedings that may be involved in this subject are also pointed out. Through a comprehensive literature search, the most relevant parameters reported are Sound Pressure Level and self-reported vocal assessments for voice parameters, and reverberation time and/or noise conditions for room acoustics. These relationships are quantified and reported while maintaining the concepts as stated in the original articles and outlining their similarities.