My long-term career goal is to discover the acoustical conditions in classrooms that minimize teachers’ vocal effort preserving high speech intelligibility for pupils. In the United States, more than 18% of the three million school teachers miss at least one day of work per year due to voice disorders. The US societal costs of voice-related teacher absenteeism and treatment expenses alone have been estimated to be as high as 2.5 billion dollars annually. High noise levels and bad classroom acoustics are frequently mentioned causal factors. To achieve this career goal, I aim to conduct fundamental and innovative research in the following main areas within the next five years:
- Singers’ strategies to preserve vocal health and their application in speech. Professional singers have the highest demands in terms of vocal load and their voice quality needs to be perfect in every performance. During training, singers learn how to modify the resonances of the vocal tract in order to increase the projection of their voice and to become less reliant on external auditory feedback in order to maintain the quality of performance, independent from the room acoustics. Resonant voice is defined as a voicing pattern involving oral vibratory sensations, particularly on the alveolar ridge and adjacent facial plates, in the context of what subjects perceive as ”easy” phonation. Acoustically speaking, the resonant voice shows differences in spectral components from the normal voice. Resonant voice shows an increase in the spectral components where the human ear is more sensitive (1-4 kHz). In consequence, consuming the same amount of energy it is possible to increase the sound perceived. I believe that many other strategies are used by singers to minimize the impact of vocal demands on the vocal folds, and I aim to identify and describe them.
- Effect of room acoustics on vocal effort and fatigue in laboratory settings.In my current research, I am moving forward on the basis of my preliminary research on this topic. I have done some pilot experiments in a laboratory setting with promising results, confirming that it possible to reduce speakers’ vocal effort by modifying acoustic parameters that are independent from the reverberation time. The next step will be the use of virtual environments, in order to test a large range of conditions with a better control of all other variables. The main parameters that I would like to test are the reverberation time and the level of external auditory feedback. Minimization of the reverberation time is very important for the improvement of speech intelligibility, while the external auditory feedback seems to be useful for reducing the teachers’ vocal effort. These two parameters, even if related, can be manipulated independently of each other. My research program will initiate the development of a baseline for a revision of classroom design in order to create the optimal acoustic conditions for both teachers and students.
- Effect of room acoustics on vocal effort and fatigue in real classrooms. Once an overarching understanding of this effect has been acquired in the laboratory, it will be necessary to evaluate its validity in a real classroom. My hypothesis is that in a real setting the magnitude of this effect will be amplified compared to the laboratory setting, as has been proven for the Lombard Effect.
- Development of new devices to decrease noise generated by students and to minimize teachers’ vocal effort. Currently, the main strategy used to address high noise levels to minimize teachers’ vocal effort and to maintain an adequate signal to noise ratio (SNR) in the classroom involves the use of an amplification system by the teacher. This provides an SNR increase of approximately 13 dB, on average. However, the use of an amplification system also increases the overall sound level in the classroom, which (1) may lead to an increase in student babble noise due to the Lombard Effect, reducing intelligibility, and (2) could result in a higher risk of hearing loss for children and teachers. The key weaknesses of the use of an amplification system are that it addresses the noise source indirectly and, therefore, does not encourage vocally healthy behavior in the children or the teacher. This research topic will lead to the development of innovative devices that will act directly on the source of the noise (students), educating the listener in noise level self-regulation and on the source of the signal (teachers), using involuntary reflexes, such as the Lombard effect, to decrease the teachers’ vocal effort.
- Classroom acoustics for enhancing students’ understanding when a teacher suffers from voice problems. Good verbal signals and low background noise are key factors for all children in order to maximize understanding of what is being taught. Classroom shape, surroundings, and even 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, factor when considering the design of a classroom. Also rarely considered is that the teacher is often teaching with a poor voice quality (e.g. hoarse voice), with the prevalence of voice problems in teachers being the highest among people who rely on voice as a tool of the trade. Teachers’ vocal problems are likely detrimental to children’s education. The purpose of this research is to determine the best classroom acoustics for students when their teacher is experiencing voice problems. Using this information, pragmatic guidelines can be put into place to give children their best opportunity for academic success, even when their teachers suffer from voice problems.
- Developing a Work-related Communicative Profile of Classroom Teachers and Instructors. Communicative disorders, defined as impairment of auditory or speech systems, constitute important health problems with important socio-economic consequences; teachers remain an under-researched group in the workplace. Studies to date are primarily based on self-reporting and currently there are no studies comparing perceptive reports to measurable data. Teachers attest to a high incidence of communicative disorders and experience limitation in activities and restriction in participation. Moreover, communicative disorders reduce productivity at work and have been associated with work-related absenteeism, hampering students’ progress. We propose a unique approach to current research, which is to collect perceptive reports and compare them to objective measurements of the teaching environment and the changes in hearing functioning and voice quality associated with noise exposure and occupational voice use. The long-term goal of this research will be to create a Workplace Communicative Health Promotion program that advocates healthy behaviors on hearing and voice among the teaching community and informs the clinicians that treat these populations.