Acoustic quality assessment in a classroom through simulations and measurements

The acoustic quality in a classroom directly impacts the educational relationship between the student and the teacher, reducing speech intelligibility. In addition, inadequate acoustic comfort burdens the vocal health of teachers. This study evaluated a classroom at the Federal University of Paraná, Campus Centro Politécnico, to verify its acoustic quality. The measurements of the acoustics descriptors: Reverberation Time (RT), Definition (D50), Central Time (Ts), Early Decay Time (EDT) were performed according to the ISO 3382-2 standard, concerning Noise Curves (NC) and Background Noise (BGN) these were evaluated by the NBR 10152 and S12.2 standards. The Speech Transmission Index (STI) was measured according to IEC 60268-16 and evaluated according to ISO 9921. The useful-detrimental ratio (U50) and the other descriptors were simulated in the ODEON software version 11. Thus, the results showed that the evaluated room did not meet the minimum requirements in terms of acoustic quality, for the descriptors RT, STI, Ts, D50, RF, and NC. Simultaneously, the RT and STI were also outside the limits established by the German and Finnish standards. Therefore, it is concluded that the evaluated classroom did not reach the minimum acoustic quality requirements.

Development and Evaluation of a Novel Mechatronic Percussion System

<p>While numerous attempts at creating mechatronic percussion systems exist, many have been limited to only playing a single membranophone or idiophone. These systems inherently lack the ability to reproduce the expressive nature of strikes which human players are capable of and often require manual reconfiguration in order to vary the striking location, type of beater or striking angle. The few which are able to pan across multiple instruments often lack the ability to perform expressively. We designed a mechatronic percussion system that provides expressivity through controllable variability of the acoustic properties inherent to percussion instruments. Our system can play across the range of an entire traditional drum kit, whether it is set up in a completely horizontal formation, vertically staggered or includes other percussion instruments. When continuously operating at maximum speed, the system is capable of playing for five hours before one subsystem is at risk of failing. Our system possesses two "wrists", each capable of gripping a variety of beaters. A single wrist can reliably perform single drum strokes at a frequency of 21 Hz, surpassing that of the world's fastest drummer. Operating both wrists results in a striking frequency of 51.9 Hz. The level of force behind each stroke and resultant acoustic quality can be controlled to produce an expressive performance. A unique feature of this system is the use of a compliant grip, applying variable pressure to the beater held and allows for a variety of beater diameters to be incorporated.</p>

Acoustic Method of Quality Control of Two-Component Composite Materials

The features of using the acoustic method for accurately determining the concentration of components in two-component composite materials by measuring the speed of sound of long waves are described in this paper. Furthermore, explicit expressions for the volume concentrations of the matrix material and reinforcing particles or fibers of composite materials obtained by acoustic measurements are found. In addition, the advantages, features, and limits of the application of acoustic quality control of composite materials of various compositions and purposes are described. It is established that the methods for determining the concentration of components are valid for all types of composite materials, which are conveniently considered as phonon crystals. These results make it possible to more accurately determine or select a measuring cell for the experimental determination of the speed of sound. The mathematical problem to be solved is a purely exact inverse problem.

Development and Evaluation of a Novel Mechatronic Percussion System

<p>While numerous attempts at creating mechatronic percussion systems exist, many have been limited to only playing a single membranophone or idiophone. These systems inherently lack the ability to reproduce the expressive nature of strikes which human players are capable of and often require manual reconfiguration in order to vary the striking location, type of beater or striking angle. The few which are able to pan across multiple instruments often lack the ability to perform expressively. We designed a mechatronic percussion system that provides expressivity through controllable variability of the acoustic properties inherent to percussion instruments. Our system can play across the range of an entire traditional drum kit, whether it is set up in a completely horizontal formation, vertically staggered or includes other percussion instruments. When continuously operating at maximum speed, the system is capable of playing for five hours before one subsystem is at risk of failing. Our system possesses two "wrists", each capable of gripping a variety of beaters. A single wrist can reliably perform single drum strokes at a frequency of 21 Hz, surpassing that of the world's fastest drummer. Operating both wrists results in a striking frequency of 51.9 Hz. The level of force behind each stroke and resultant acoustic quality can be controlled to produce an expressive performance. A unique feature of this system is the use of a compliant grip, applying variable pressure to the beater held and allows for a variety of beater diameters to be incorporated.</p>

Improving Building Acoustics

One of the most significant aspects which need to be analysed in the case of a building consists in finding that the sound level perceived by listeners is a proper one (Daniela-Roxana Tămaş-Gavrea et all., 2012). Their inconsistent spreading can develop problems in audition which can be solved only by putting in work a number of measures of acoustic rehabilitation. The evaluation of the acoustic quality of a building is a delicate issue, because of the complex system of the sound field contained in closed spaces and the sound features of the outlining surfaces. This paper presents a research on improving the acoustic conditions of a building which initially had a technical-administrative destination and was then converted into an office building (Stanca S.E., 2021). The measures of acoustic protection were recommended with a view to mitigate the noise level under admissible limits in the functional unit under consideration.

The influence of perceived environmental quality on thermal comfort in an outdoor urban environment during hot summer

Thermal comfort in outdoor spaces is essential for human health and human wellbeing. A comfortable outdoor space enhances urban livability and sustainability. Previous studies on outdoor human thermal comfort highlighted that apart from the microclimate conditions, the psychological and physiological factors play an important role in human thermal comfort. The influence of environmental quality on human thermal comfort is being examined in this paper. A survey with a total of 1842 thermal comfort responses was conducted during a hot summer in Hong Kong. Perceived aesthetic and acoustic quality votes are strongly associated with Thermal Sensation Votes (TSV). Thermal Comfort Votes (TCV) in the satisfied aesthetic group and the satisfied acoustic group are significantly higher than that in the not satisfied group. A sensation of comfort was confirmed by 39.8% and 38.4% of participants in the satisfied aesthetic group and the satisfied acoustic group, while only 22.2% and 23.9% of the members of the not satisfied group felt comfortable. The study suggested that the perceived environmental qualities are highly associated with thermal sensation and thermal comfort, and a beautiful and quiet environment can improve the thermal comfort and thermal tolerance.

Environmental Acoustic Comfort in the Built Environment

The acoustic quality of classrooms has a strong influence on the teaching and learning process. This interference assessed using the impulsive technique to measure the rate of speech transmission (STI), reverberation time (RT) and sound definition (D50). These are the most relevant acoustic descriptors in the assessment of classrooms, where verbal exposure is the means of communication between teachers and students. The evaluation took place in two buildings of the Federal University of Paraná (UFPR), built in the 1960s and another in 2016. The measured values ​​of STI, provided in the classrooms' actual acoustic conditions, were used as an adjustment parameter for simulations made with the software ODEON. After carrying out the measurements and simulations, the dimensioning of improvements was possible. The acoustic simulations presented suggestions to qualify the quality of the classrooms' acoustic comfort, ensuring that teaching and learning to do not suffer losses due to the physical structure of the classrooms. The measured values ​​of STI, RT and D50 show that, in the old building, except for a single classroom that preserves the original ceiling that had a high sound absorption coefficient, it has reasonable values, below the ideal for classrooms, according to the IEC 60268-16 (2011) standard. The investigation showed that the rooms with a roof replaced by a PVC covering had a sharp drop in acoustic quality. The newest building has classrooms with proper acoustic comfort conditions.

Optimizing the use of acoustic materials in office buildings

Office space designers encounter a challenge in identifying the optimal set of noise control materials to improve the acoustic quality while keeping the cost of selected acoustic materials to a minimum. To address this challenge, this paper presents a novel optimization model that provides the capability of minimizing the cost of acoustic materials while satisfying all designer-specified acoustic quality requirements. The model is developed in five main stages that focus on (1) identifying the correlated designer decisions that influence the model objective function; (2) formulating an optimization objective function; (3) identifying the model constraints that are organized into acoustic quality and materials selection constraints; (4) implementing the model using genetic algorithms (GA); and (5) evaluating the performance of the model using an office space design that is under construction to assess and improve the model feasibility and performance. The outcome of the performance evaluation stage illustrates the novel capabilities of the developed model in identifying the optimal selections for the type and area of acoustic material for each surface in the office space that achieve the desired acoustic quality while keeping the cost of selected acoustic materials to a minimum.