Birgit Rasmussen

Speaker-Oriented Classroom Acoustics Design Guidelines in the Context of Current Regulations in European Countries

Summary Most European countries have regulatory requirements or guidelines for reverberation time in classrooms which have the goal of enhancing speech intelligibility and reducing noise levels in schools. At the same time, school teachers suffer frequently from voice problems due to high vocal load experienced at work. With the aim of improving working conditions for teachers, this article presents guidelines for classroom acoustics design that meet simultaneously criteria of vocal comfort and speech intelligibility ,w hich may be of use in future discussions for updating regulatory requirements in classroom acoustics. Tw or oom acoustic parameters are shown relevant for as peaker: the voice support, linked to vocal effort, and the decay time derive df rom an oral-binaural impulse response, linked to vocal comfort. Theoretical prediction models for room-averaged values of these parameters are combined with am odel of speech intelligibility based on the useful-to-detrimental ratio and empirical models of signal-to-noise ratio in classrooms in order to derive classroom acoustic guidelines, taking into account physical volume restrictions linked to the number of students present in ac lassroom. The recommended values of reverberation time in fully occupied classrooms for flexible teaching methods are between 0.45 sa nd 0.6 s( between 0.6 and 0.7 si na nu noccupied bu tf urnished condition )f or classrooms with less than 40 students and volumes belo w2 10 m 3 .W hen designing larger classrooms, ad edicated acoustic study taking into account considerations about geometry ,m aterial and speaker/audience placements should be made, which can help to increase the voice support and reduce the vocal effort.

Neighbour and traffic noise annoyance: a nationwide study of associated mental health and perceived stress

Background Noise exposure is a well-known risk factor for multiple adverse health effects. Annoyance is the most prevalent response to environmental noise and may result in negative emotional responses, including poor mental health and high levels of perceived stress. The aim of this study was to investigate the association between neighbour and traffic noise annoyance, and mental health and perceived stress. Methods Data were derived from the Danish Health and Morbidity surveys in 2010 and 2013. The study was based on a random sample of the adult population in Denmark living in multistorey housing (n = 7090). Information on neighbour and traffic noise annoyance during the past 2 weeks, and mental health and perceived stress, using Short Form-12 and Perceived Stress Scale instruments, respectively, was obtained by means of self-administered questionnaires. Multiple logistic regression models were used to examine the associations between noise annoyance and poor mental health, and high perceived stress levels, respectively. Results Those who reported being very annoyed by neighbour noise had 2.34 [95% confidence interval (CI): 1.83-2.99] times higher odds of having poor mental health and 2.78 (95% CI: 2.25-3.43) times higher odds to experience a high level of perceived stress than individuals not annoyed by noise from neighbours. Similar associations were observed with traffic noise annoyance. Conclusion The results from this study indicate that there is a strong relationship between noise annoyance and poor mental health and high levels of perceived stress among individuals living in multistorey housing in Denmark. Future studies are needed to determine the direction of causality.

A pilot study on acoustic regulations for office buildings—Comparison between selected countries in Europe

Acoustic regulations or guidelines for office buildings are found in several countries in Europe. The main reason is to ensure satisfactory acoustic working conditions for the various tasks and activities taking place in the many different kinds of rooms in such buildings. Examples of room types are offices, meeting rooms, open-plan offices, corridors, reception areas, dining areas, all with different acoustic needs. Some countries specify a few acoustic limit values only, while others define several different criteria, guidelines only, or a combination of requirements and guidelines. As a pilot study, comparison between requirements in selected countries in Europe has been carried out. The findings show a diversity of limit values for acoustic requirements. The paper includes examples of requirements for reverberation time, airborne and impact sound insulation, noise from traffic and from service equipment. Examples of guidelines will also be presented. The discrepancies between countries are being discu...

Meta-analysis of subjective-objective sound insulation data

A smaller meta-analysis using field data for subjective sound insulation in dwellings is carried out, using and analyzing data found in the literature. The investigated parameter is the correlation coefficient between the sound insulation metrics and the subjective annoyance (or similar). Both airborne and impact sound insulation is considered. One of the objectives are to see if low frequency adaptation terms according to ISO 717 will yield an increased correlation or not. Other investigated aspects is the influence of lightweight versus heavyweight building elements and the question regarding the importance of vertical versus horizontal transmission.

Acoustic regulations for housing and schools in Europe and South America – A pilot study in 2016

Acoustic regulations for housing and schools exist in most countries in Europe, the main reasons being protection of health of citizens in their homes and optimizing learning and work conditions in schools. Comparative studies in Europe have shown a high diversity of descriptors and limit values for acoustic requirements. Considering globalization and noise as a health issue, it is important to extend attention to other parts of the world and establish dialogue and cooperation. As a pilot study, acoustic regulations in three countries in South America, namely Argentina, Brazil and Chile, have been considered. The findings indicate weaker requirements than typical in Europe, although at both continents there is a joint challenge to review regulatory requirements in those countries needing improvement of acoustic conditions in housing and schools. It is concluded that one of the first steps is to create awareness among authorities and building industry and to exchange experience about construction solutions...

Some consequences of including low frequencies in the evaluation of floor impact sound

A method for including frequencies down to 50 Hz in the evaluation of floor impact sound has become available with the new version of ISO 717‐2. In addition to the single number quantity for rating the impact sound insulation, a new spectrum adaptation term has been defined. The method has been studied by the Acoustics Group of NKB (Nordic Committee on Building Regulations). The new method has been applied to a large number of recent measuring results from the Nordic countries. It was found that the spectrum adaptation term for the extended frequency range depends on the type of floor construction, and light floor constructions are evaluated less favorably than heavy constructions. Comparison with data from a 14‐year‐old Swedish survey suggests that the extended frequency range leads to a higher correlation with subjective evaluation of impact noise. The consequences of applying the extended frequency range in future building regulations or in a system for sound classification of dwellings have been consi...