School teachers appear to have a greater prevalence of voice problems than the general population, yet classrooms are not designed with the safe use of teachers' voices in mind. In an effort to better understand the influence of classroom acoustic design on teachers' voice parameters measurements of teachers' voices in different classroom types have been made. An Ambulatory Phonation Monitor (APM) has been used to measure voice parameters (including the average voice sound pressure level, fundamental frequency and phonation time) directly from the skin vibrations in the neck, thus eliminating the effects of other noise sources in the environment. The rooms involved were acoustically benchmarked individually to enable relationships between the voice data and acoustic parameters, such as unoccupied ambient noise levels and reverberation times, to be investigated. The study data shows a positive correlation between unoccupied ambient noise levels and the average voice levels of the teachers, as well as between voice level and phonation time. There was no significant correlation in the study data between classroom reverberation times and voice levels or between voice level and fundamental frequency.

Sound diffusion refers to the ability of a surface to evenly scatter sound energy in both time and space. However, omni-directional radiation of sound, or perfect diffusion, can be impractical or difficult to reach under traditional means. This is due to the considerable size required, and the lack of tunability, of typical quarter-wavelength scattering strategies necessary for producing the required complexity of the surface acoustic impedance. As such, it can be a challenge to design sound diffusing structures that can display near perfect diffusion performance within slim dimensions. In this work, we propose a method for obtaining quasi-perfect and broadband sound diffusion coefficients using deep-subwavelength acoustic diffusers, i.e., metadiffusers. The relation among the geometry of the metasurface, the bandwidth, and the diffusion performance is analytically and numerically studied. For moderate bandwidths, around 1/3 of an octave, the method results in nearly perfect sound diffusion, while for a bandwidth of 2.5 octaves, a normalized diffusion coefficient of 0.8 was obtained using panels 1/30th thinner than traditional phase-grating designs. The ratio between the wavelength and the size of the unit cell was identified as a limitation of the performance. This work demonstrates the versatility and effectiveness of metadiffusers to generate diffuse reflections outperforming those of classical sound diffusers.

Music is complex. There are risks to hearing health associated with playing due to excessive sound exposure. Face the Music is an on-going cross-sectional project to assess the risks to unamplified classical musicians. Key findings over the first fifteen years are presented based on the research undertaken with a leading conservatoire on more than 5000 classical music students. The work covers hearing health surveillance, education and awareness, sound exposure, and new technology. The future of the research programme is discussed along with opportunities in objective hearing health assessment and new acoustic solutions. A lot has changed in fifteen years, but the research was driven by a change in United Kingdom legislation. It is hoped that the research results can inform future regulation.

This paper investigates the interrelation of room acoustics parameters as measured in lecture theatres/classrooms using four sound source configurations. Ten typical rooms were selected as representative of university premises and measured to ISO 3382 standards. The study focuses initially on the type of sound source used, to establish the suitability of multi source based measurements in assessing the acoustics of classrooms. Acoustic performance is then discussed in the context of the relationship between room acoustics parameters with and without significant background noise, with a particular focus on speech intelligibility. To facilitate a more efficient discernment of results, EDT, T ₃₀ , Clarity indices and MTI were considered, as they are commonly included in general room acoustics assessments. Either of the source configurations was found to be suitable for performing general purpose measurements in (small) rooms. Clarity and EDT were found to be linearly related to the modulation transfer index in noiseless conditions, in line with earlier findings, thus an excellent predictor of STI. Background noise could be ascertained as of primary importance in the case of a non linear relation.

Introduction: The noise emissions from the operation of heliports situated in cities can have significant adverse impacts on a large number of local residents. Despite its significance, the effect of noise from rotary aircraft operation in an urban setting has not been extensively studied. Objective: This paper presents for the first time an objective and subjective investigation into the noise emissions from the London Heliport and the associated impact on local residents. Method: Long-term noise monitoring measurements were taken at four locations and a social survey was implemented involving over 1500 respondents. A new objective measurement methodology was designed and developed that allowed individual air movements from the Heliport to be acoustically identified. Subjective results were contrasted with relevant social surveys and to the objective results. Objective results were also compared to planning guidance, local operation conditions and national and international based noise assessment criteria. Results: Excessive sound levels were found, both internally and externally, which can be attributed directly to the operation of the Heliport. The high participation rate obtained in the social survey confirmed that noise emissions from the heliport operation cause important/substantial adverse impact on quality or life and well-being of the majority of respondents. Conclusions: The level of annoyance reported by respondents appeared higher than the level of annoyance attributed to the noise measurements at monitoring sites. As a study first of its kind, it is expected that the findings will inform and influence future regulatory policy and consequently improve the well-being of many residents.

Many studies have suggested that teachers have a significantly higher rate of voice problems than the general population. In order to better understand the possible influences of room acoustics on different voice parameters, a study has been carried out by London South Bank University which involved measurements of voice parameters for teachers working in classrooms with varying acoustic conditions. Data relating to the voice, including the average speech sound level, fundamental frequency, and phonation percentage, were captured using an Ambulatory Phonation Monitor (APM) which measured directly from skin vibrations in the neck, thereby excluding the effects of other noise sources in the environment. The measured voice parameters were compared with the room acoustic data for the classrooms involved, which were surveyed separately from the voice measurements. In addition to the field measurements, an online questionnaire was undertaken with the support of two UK teacher trade unions. This was designed to gain further information on teachers’ experiences of voice problems and school acoustics in general and indicated that over 66% of the surveyed teachers had experienced voice problems during their career. This paper will present the results of the field measurements and questionnaire survey.