| 1. |
- Möllerström, Erik, 1984-, et al.
(författare)
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Noise Propagation from a Vertical Axis Wind Turbine
- 2014
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Ingår i: Proceedings of 43rd International Congress on Noise Control Engineering. - Brisbane, QLD : Australian Acoustical Society. - 9780909882020 - 9780909882037 - 9780909882044
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Konferensbidrag (refereegranskat)abstract
- Initial noise measurements were performed on a 200kW vertical axis wind turbine (VAWT) and results were compared to that of a Vestas V27, a similar size horizontal axis wind turbine (HAWT). Multiple recording units were placed in line downwind of the turbine to investigate noise propagation. The frequency distribution of the noise were analyzed indicating that the VAWT has lower relative levels for frequencies under 3000 Hz, especially within 600-1200 Hz. Furthermore, VAWT noise seems to occur more around the same frequencies as the natural background noise, increasing masking probability. Results from propagation measurements seemed to indicate that noise declines more rapidly with distance for the VAWT then for the reference HAWT, possibly explained by the lower levels at low frequencies. Further investigation is needed to establish these differences and the 200 kW VAWT creates an opportunity doing so utilizing arguably the largest operational VAWT existing today.
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| 2. |
- Bard, Delphine, et al.
(författare)
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Challenges for acoustic calculation models in "silent timber build", Part 1- FEM
- 2014
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Ingår i: INTERNOISE 2014 - 43rd International Congress on Noise Control Engineering : Improving the World Through Noise Control - Improving the World Through Noise Control. - 9781634398091 - 9780909882037 ; , s. 4424-4429
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Konferensbidrag (refereegranskat)abstract
- The project "Silent Timber Build" will develop new prediction tools for timber structures. There are several challenges that have to be overcome to provide a full prediction tool. The differences in weight, stiffness and density for wooden structures compared to traditional, heavy and more homogeneous structural material have repercussions on how the sound propagates throughout the structures, affecting the sound and vibration insulation performance and also theories to be used in prediction models. Finite element simulations have proved to be useful in the design phase in a certain low and very low frequency range. By further developing reliable finite element tools for low frequencies, the performance of future wooden constructions can be predicted in a full frequency range, saving both time and money as all calculations, and modifications can be done during the design phase. However the upper limit for using FEM has to be further investigated and then be merged with statistical methods. This article, following another article Part 2, will focus on medium and high frequency range calculations. For full-scale building, Virtual SEA method, as analytic and SEA approaches will be used in frequencies low enough in order to optimize the overlap to FEM.
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| 3. |
- Ejsmont, Jerzy, et al.
(författare)
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Tyre/road noise reduction by a poroelastic road surface
- 2014
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Ingår i: INTERNOISE 2014 - 43rd International Congress on Noise Control Engineering. - 9780909882037
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Konferensbidrag (refereegranskat)abstract
- Low noise road surfaces of existing types may in favourable cases and in new conditions provide up to 7 dB of noise reduction. For higher noise reductions, innovative solutions must be sought. Poroelastic road surfaces (PERS) may be such a solution, which currently is studied in the EU project PERSUADE. This paper presents results of trials with a PERS version prefabricated by one of the project partners. Tests were made in a laboratory at TUG, where different tyres were tested on drums covered with PERS, and later field tests were made on a local street in Sweden where VTI had constructed a 25 m long trial section. The field tests were made with a CPX trailer from TUG. Both laboratory and field results showed that tyre/road noise reductions of 9-11 dB were achieved compared to a dense asphalt concrete pavement with maximum aggregate size 11 mm. This is the best result so far in the project. At the same time, this PERS, despite being relatively soft, reduces rolling resistance of passenger car tyres to record-low values, which is important for reducing fuel consumption and CO2 emissions. It is concluded that this type of prefabricated poroelastic road surface offers a very efficient way of reducing tyre/road noise, provided current durability problems can be solved.
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| 4. |
- Hagberg, Klas, et al.
(författare)
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Low frequency sound transmission in multifamily wooden houses
- 2014
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Ingår i: INTERNOISE 2014 - 43rd International Congress on Noise Control Engineering : Improving the World Through Noise Control - Improving the World Through Noise Control. - 9780909882037 - 9781634398091 ; , s. 4455-4461
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Konferensbidrag (refereegranskat)abstract
- In the recently finished research projects, AkuLite and AcuWood, it is clearly stated that low frequencies should be considered far more, prior to design new wooden structural building system. Lower than 50 Hz is preferable, and the most annoying frequencies appear between 20 and 50 Hz. However, it is still a long way to go in order to convince acousticians, the entire global industry and authorities that these frequencies have to be considered in order to build wooden structures which are experienced by the habitants as equally good as heavy structures. To "save" the industry, a lower limit of at least 50 Hz at least for impact sound should be mandatory in the near future globally, in spite of the fact that the new standard ISO 16717 will not be reality. This paper describes the main reasons why it is needed to include these low frequencies in residential buildings. It describes different constructions and their appearance due to low frequency impact sound transmission. The paper comprises some examples designed to fulfill the Swedish requirements, which equals Ln,Tw and Ln,Tw+CI,50-2500 ≤ 56 dB between dwellings. It comprises also a discussion regarding optimizing constructions for various uses, e.g. different types of housing.
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| 5. |
- Hynninen, A., et al.
(författare)
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Acoustic two-port simulation model for the particle oxidation catalyst (POC®)
- 2014
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Ingår i: INTERNOISE 2014 - 43rd International Congress on Noise Control Engineering. - 9780909882037
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Konferensbidrag (refereegranskat)abstract
- The reduction of the exhaust noise from internal combustion engine (IC-engine) is mainly managed by proper silencer design, while less attention is paid to the acoustic performance of the after treatment devices (ATD). It is known from the earlier studies, that the transmission loss of a typical ATD unit can be quite significant. An ATD unit for diesel engines is classically assembled from several specific parts such as selective catalytic reducers (SCR), diesel oxidation catalysts (DOC) and diesel particulate filters (DPF). One new alternative to the conventional DPF is the particle oxidation catalyst (POC®). The substrate used in the POC-X type filter consists of fine, corrugated metallic wire mesh screens piled askew and rolled into a cylindrical shape. In this paper an acoustic two-port simulation model for POC-X is sought starting from the classical Kirchhoff solution for prediction of the acoustic wave attenuation in narrow channels. According to experimental studies, correction factors to the narrow channel two-port model are proposed.
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| 6. |
- Kouyoumji, Jean Luc, et al.
(författare)
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Challenges for acoustic calculation models in "Silent Timber Build", Part 2
- 2014
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Ingår i: 43rd International Congress on Noise Control Engineering (INTERNOISE 2014) : Improving the World Through Noise Control - Improving the World Through Noise Control. - 9781634398091 - 9780909882037 ; , s. 3054-3061
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Konferensbidrag (refereegranskat)abstract
- The project "Silent Timber Build" will develop new prediction tools for timber structures. There are several challenges that have to be overcome to provide a full prediction tool. The differences in weight, stiffness and density for wooden structures compared to traditional, heavy and more homogeneous structural material have repercussions on how the sound propagates throughout the structures, affecting the sound and vibration insulation performance and also theories to be used in prediction models. The project will use Finite element simulations (FEM) and Statistical Energy Analysis (SEA) approaches to predict acoustical behavior of light weight timber constructions. This article, following another article Part 1, will focus on medium and high frequency range calculations. Statistical methods will be used in the medium and high frequency, where the acoustic performance of wooden building components (walls and floors) is generally limited by the presence of structural links and couplings. Statistical Energy Analysis (SEA) has proven to be an efficient approach, providing robust vibroacoustic models in this frequency region. The extension of statistical methods towards the low frequencies has to be evaluated, especially regarding time responses of impact noise on floor systems. For full-scale building, Virtual SEA method will be used as well as analytic SEA approach in frequencies low enough in order to optimize the overlap to FEM.
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| 7. |
- Larsson, Conny, 1952-, et al.
(författare)
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Wind turbine sound - metric and guidelines
- 2014
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Ingår i: Proceedings of 43rd International Congress on Noise Control Engineering. - Melbourne, Australia. - 9780909882037
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The meteorological conditions vary over the globe but also change over the day and the year and vary a lot depending on the terrain for a certain location. The meteorological parameters govern both the wind turbine emission sound levels and the sound propagation conditions and therefore gives rise to different sound immission levels. Long-time measurements of meteorological effects on sound propagation from wind turbines over forest areas have been performed at two sites in Sweden for more than two years. One site is located in the southern part with flat terrain and the other site is located in the northern part of Sweden with more hilly terrain. The aim of the project is to improve the knowledge of sound propagation from wind turbines and especially over varying terrain and weather conditions. Control measurements of wind turbine immission sound levels will be needed to see that they fulfill the noise regulations. It is therefore of most importance to be able to make representative measurements. Discussions about under what meteorological conditions the immission measurements have to be carried out, the sound metric and the impact of the guidelines are presented in this paper.
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| 8. |
- Leav, O. Y., et al.
(författare)
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A novel semi-active quasi-zero stiffness vibration isolation system using a constant-force magnetic spring and an electromagnetic linear motor
- 2014
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Ingår i: INTERNOISE 2014 - 43rd International Congress on Noise Control Engineering. - 9780909882037
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Konferensbidrag (refereegranskat)abstract
- The performance of conventional vibration isolation systems are limited by the stiffness of the mount required to support the weight of the payload. A potential method for addressing this limitation is to use the phenomenon of quasi-zero stiffness (QZS), which results in a high static stiffness to support the weight of payload and a low dynamic stiffness to achieve a wider vibration isolation range. Recently, QZS systems with various negative stiffness elements and mechanical configurations have been proposed and studied. This paper presents the design and analysis of a novel semi-active QZS vibration isolation system using a commercial constant-force magnetic spring and an electromagnetic linear motor. The proposed system combines the advantages of both passive QZS systems and active damping control, and therefore is cost-effective, energy-efficient, and has the potential of a large bandwidth of vibration isolation as well as a low resonance peak. The use of acommercial magnetic spring not only allows the system to support a large static pay load over a wide range of travel but also simplifies the design. In this paper, the design, identification and control aspects of the proposed vibration isolation system are discussed and the system performance is investigated theoretically and experimentally.
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| 9. |
- Negreira, Juan, et al.
(författare)
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Determination of vibration acceptability and annoyance design indicators for human response to wooden-floor vibrations
- 2014
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Ingår i: 3rd International Congress on Noise Control Engineering: Improving the World Through Noise Control, INTERNOISE 2014. - 9780909882037
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Konferensbidrag (refereegranskat)abstract
- The vibrational response of wooden floor systems is an issue that needs to be dealt with more adequately. Notably, studies addressing human response to vibrations are needed in order to better estimate what level of vibrations in dwellings can be seen as acceptable. In this investigation, measurements on five different floors were performed in a laboratory environment at two locations in Sweden. Acceleration measurements were carried out while a person either was walking on a particular floor or was seated in a chair placed there, as the test leader was walking on the floor. These participants filled out a questionnaire regarding their perception and experiencing of the vibrations. Independently of the subjective tests, acceleration measurements were also carried out, using a shaker as excitation source, with the aim of determining the dynamic characteristics of the floors. In addition, static load tests were performed using displacement gauges so as to measure the floor deflections. The ultimate aim was to develop indicators of human response to floor vibrations, specifically those regarding vibration acceptability and vibration annoyance, their being drawn based on relationships between the questionnaire responses obtained and the parameter values determined on the basis of the measurements carried out.
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| 10. |
- S.youssef, Rabab, et al.
(författare)
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Acoustical quality assessment of lecture halls at Lund University, Sweden
- 2014
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Ingår i: 43rd International Congress and Exposition on Noise Control Engineering (Internoise 2014) : Improving the World Through Noise Control - Improving the World Through Noise Control. - 9781634398091 - 9780909882037 ; , s. 1382-1391
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Konferensbidrag (refereegranskat)abstract
- Noise control in buildings should aim at reducing disturbances caused by speech noise (i.e., improve speech privacy, speech intelligibility). Room acoustics can be controlled with high room absorption, high screens and bookcases, and sufficient masking sound. This research concerns as important aspect of room acoustic metrology, the ability to quantify the most relevant room acoustic parameters for academic purposes. In this proposed study we will focus on the lecturing rooms of Lund University, of which some have designed quite recently while others were constructed many years ago. As the use of audio- visual equipment as well as the use of enabling techniques for disabled students is continuingly increasing. Lecture halls, which have not been explicitly designed for the use of such equipment, are being fitted with an assortment of audio-visual fixtures. This can lead to far less environment profoundly impacts the outcome of the learning process it is performance to assess the current state of the situation with respect to the acoustic performance of lecture halls at Lund University.
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