4:00pm - 4:15pm
On the Low Frequency Impact Noise Measurement in Residential Buildings
1Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Materials Engineering and Physics, Radlinského 11, 810 05 Bratislava, Slovakia; 2A&Z Acoustics s.r.o., Víťazná12, 831 06 Bratislava, Slovakia
The propagation of low-frequency (LF) noise in buildings is a common topic in building acoustics nowadays. In practice, we commonly encounter cases that, despite the fact that buildings meet normative requirements, people are disturbed by unwanted noise generated by walking and other sources of impact noise. However, these complaints from building users can be avoided by the correct design of construction solutions. It is not unusual that in practice the designer often moves on the edge of the required criteria in order to reduce the cost of constructions and its parts. In this article, we selected 4 cases of flats where complaints from residents about high levels of impact noise were recorded although the construction meets the requirements set out in the standard. Based on the obtained documentation, BEM (Boundary Element Model) and FEM (Final Element Model) models were created, where we simulated the distribution of acoustic pressure in an enclosed space and compared different methods of spatial averaging of the resulting acoustic pressure. The article also discusses the currently set requirements for the evaluation of floor structures in selected countries.
4:15pm - 4:30pm
Acoustic design and optimization of an organic architecture, a cross disciplinary design of an open-space airport case study.
1Department of Civil, Environmental, Land, Building Engineering and Chemistry, Polytechnic University of Bari, 70125 Bari, Italy; 2Deerns Italia S.P.A., 20149 Milan, Italy
Architectural innovation, both at morphological and technological scale, have increased the importance of new methodologies and tools for the building performance analysis. New organic shapes have decreased the reliability of traditional specialistic knowledge, highlighting the importance of new methodologies to manage complex models and analyse the indoor comfort. The aim of this paper is to present a case study of the acoustic design of an organic open-space airport, realized integrating architectural and acoustic concepts in the design workflow since the early stages of the design process. The building, characterized by a curvilinear plan, a wavy suspended ceiling, and a tilted façade, behave as a single tall large volume containing different small low-height closed service boxes (shops, toilets, …). This architectural approach leads to a mixture of functions in the same large volume with a resulting complex problem of acoustic optimization. To evaluate the acoustical behaviour, different studies have been conducted from the protection from external noise, to the optimization of the reverberation time, to the design of the speakers to optimize the Speech Transmission Index (STI), and to the evaluation of the non-closed partitions insulation through architectural acoustic. Considering the geometric complexity of the airport, different tools and a particular methodology have been used to properly model the building and to optimize the use and the placement of acoustic absorbing materials. The organic initial model, realized in Rhinoceros v.5, has been firstly discretized through a proper transformation of Non Uniform Rational Basis-Splines (NURBS) surfaces in meshes keeping the right shape; hence, sources and receivers, placed inside the model, have been translated in coordinates thanks to a Grasshopper algorithm. Then, exporting this model properly simplified, all materials have been assigned in SkecthUp and finally – through the SU2CATT plugin – the model has been imported in CATT-Acoustic to run the analyses.
4:30pm - 4:45pm
Airborne sound insulation of single-leaf partitions under hygric load
Fraunhofer IBP Stuttgart, Germany
In buildings of all types the use of single-leaf partitions are recommended, not least for reasons of cost efficiency and possible resource optimisation. In addition to the familiar building physics topics they play also a particularly important role in noise protection.
Numerous factors influence the acoustic properties of single-leaf, plate-shaped and dry partitions. These include the mass, the bending stiffness, the position of the critical frequency and the total loss factor of the partition as well as the stimulating frequency of the airborne sound, the sound incidence angle or the characteristic impedance of the air. Each mineral wall-building material has its own product-specific pore structure. In the usual calculation of the airborne sound insulation of single-leaf, airtight and dry partitions, this has so far not been taken into account. It is precisely in these building material pores that a hygrothermal, continuous adjustment of the moisture content takes place in addition to the production-related water quantities.
This changes the mass of the building component and thus the airborne sound insulation of the wall. In addition to this well-known mass effect, a further mechanism, which has not yet been considered, increases airborne sound insulation: the smaller the pore sizes in the building material, the greater the mechanical forces caused by stored pore water. The existing equations for airborne sound insulation do not take these effective forces into account and must therefore be extended. The wall building material is considered as a porous medium with solid and fluid components. The new calculation approach allows the calculation of the airborne sound reduction index for single-leaf partitions under hygric load for saturated and partially saturated moisture conditions with high accuracy. The calculation results provide valuable information for the planning and product development of new building materials.
4:45pm - 5:00pm
Effect of competitive acoustic environments on speech intelligibility
1Politecnico di Torino, Italy; 2Carl von Ossietzky Universität and Cluster of Excellence Hearing4All, Oldenburg, Germany
Excessive noise and long reverberation times degrade the ability of a listener to discriminate target voices in everyday life environments. This is particularly true for school settings where learning is delivered and students develop their cognitive abilities. Most classrooms in Italy are settled in historical buildings with big volumes and vaulted ceilings that generate competitive acoustic environments. Furthermore, listeners are nowadays immersed in classrooms that include students with different mother tongues, backgrounds and cognitive deficit too, thus it is necessary to develop strategies for the enhancement of speech intelligibility that account for different premises at the same time. So far, literature lacks in the data on the effect of real acoustics on speech intelligibility and on the spatial release from masking, as research has primarily focused on such effects under laboratory conditions and not ecologically. Also, the effect of noise on speech intelligibility was widely investigated considering its energetic rather than its informative content.
Therefore, a first study involving normal hearing adults was carried out presenting them listening tests via headphone and considering the competitive real acoustics of two primary-school classrooms with reverberation time of 0.4 s and 3.1 s, respectively. The main objective was the investigation of the extent to which the spatial release from masking is affected by reverberation and noise under real classroom acoustics, in order to help the design of learning environments. Binaural room impulse responses were acquired at increasing speaker-to-listener distances, with noise sources at different azimuths from the listener’s head. The spatial release from masking was significantly and negatively affected by noise type and reverberation. Longer reverberation times brought to worst speech intelligibility, in terms of speech reception thresholds, higher by 6 dB on average. The presence of noise with and informative content was detrimental by 7 dB with respect to an energetic noise.
5:00pm - 5:15pm
The influence of suspended ceilings on the impact sound insulation of wooden-beamed ceilings in a Wilhelminian style house
1Technische Universität Wien, Austria; 2Gassner & Partner Baumanagement GmbH, Austria
The refurbishment of Wilhelminian style houses, driven by the densification of the living space, is increasingly leading to problems in the field of sound insulation. The high-quality refurbishment of the outer shell of the existing buildings significantly reduces the basic noise level in living rooms. As a result, users are perceived as more sensitive to in-house sound emissions and in particular the impact sound from foreign usage units as annoying.
The focus of the project and the work shown is to improve the impact sound insulation of wooden beamed ceilings in Wilhelminian style houses without adding floor height. This ceiling systems show significant differences in its basic constructions compared to the modern wood-beamed ceilings (beam dimensions, spans width, etc.). For this reason, a transfer of the findings from existing research is only possible to a limited extent. At present, there is no reliable catalogue of measures for those type of ceilings.
The work shown examines different suspended ceilings constructions on a wood-beamed ceiling in a Wilhelminian style house. The conclusions are based on the measurement of the impact sound level in different construction phases according to ÖNORM EN ISO 16283-2:2018. The investigated suspended ceilings vary in planking material, cavity damping material and suspension system. The constructions examined show differences of up to 15dB in the considered one third octave bands of the improvement of the impact sound level.
An unknown influence are openings, in large numbers, in the suspended ceiling. These are often caused by the installation of lighting or by ventilation systems. Different opening cross-sections regarding their influence of impact sound insulation by the suspended ceiling are investigated. The results show that depending on the resulting cross-sectional area of the holes, a reduction in the impact sound insulation is recognizable and should be considered in the planning process.