Noise can be defined as unwanted sound. There are many cases and applications that reducing noise level is of great importance. Loss of hearing is only one of the effects of continuous exposure to excessive noise levels. Noise can interfere with sleep and speech, and cause discomfort and other non-auditory effects. High level noise and vibration lead to structural failures as well as reduction in life span. The importance of noise issue could be well understood by looking at regulations that have been passed by governments to restrict noise production in society. Industrial machinery, air/surface transportation and construction activities are main contributors in noise production or "noise pollution". Noise Pollution is not only an annoyance; it is an environmental health hazard. Noise can be found anywhere that life exists, in forests, in the workplace, in homes acrossAmericaand even under water. A lot of research has been done about noise pollution in the last 40 years, but yet there is still more to learn about how to control and lessen the affects that noise has on human and animal life. Noise control is a major factor in the planning, design, and construction of transportation corridors. Architects, acoustical engineers and transportation planners are searching for creative ways to eliminate or greatly reduce noise levels. The challenge lies in attaining desired sound levels while simultaneously maintaining or enhancing the visual environment. I will be setting up an experiment to determine what kinds of materials absorb sound waves of varying frequencies most effectively.

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The standard, EN12354-1 describes a simplified statistical energy analysis (SEA) model to predict the apparent sound reduction index between two rooms inclusive of the contributions of the flanking paths. There is interest worldwide in applying the EN12354 model to lightweight building elements. However, lightweight elements typically do not meet the requirements of an SEA subsystem and therefore applying the EN12354 model to these elements may result in inaccurate predictions. The purpose of this investigation was to systematically evaluate the application of the EN12354 model to lightweight building constructions. The evaluation included the determination of the probability density functions and the propagated uncertainty of the calculations. Knowledge of the probability density functions resulted in alternative calculations of the structure-borne sound transmitted through the constructions. The uncertainty analysis revealed that the uncertainty of the predictions is directly affected by the variance of the vibratory field measured on the elements. The vibratory fields of lightweight elements typically show large variances and therefore the propagated uncertainty of the EN12354 predictions for these elements can be significant. The investigation included measurements both in the laboratory and in the field. The results of the laboratory measurements were compared to both predictions using the EN12354 methods and ESEA models which included higher order flanking paths and non-resonant transmission paths. The field measurements included in this investigation were unique because the flanking intensity sound reduction indices of the elements in the source room were measured. The measurements allowed for the EN12354 predictions for each flanking element to be assessed instead of just the apparent sound reduction index between the rooms. The study resulted in proposed correction factors for when reciprocity does not hold and proposed changes to ISO10848 to improve the accuracy of the predictions when the EN12354 method was applied to lightweight building elements. However, neither the proposed correction factors nor the proposed changed to ISO10848-1 could correct for the potentially large differences between the predicted and the measured results. Based on the findings of this study, the use of the EN12354 model for the calculation of the apparent sound reduction index of lightweight elements is not endorsed. Lightweight constructions may not be categorized as ideal SEA subsystems due to the lack of diffuseness of the vibratory field. Furthermore, in order for EN12354 to be applied to lightweight constructions, a reliable method of calculating the resonant component of the sound reduction index of double-leaf elements is required. Therefore, statistical methods including the EN12354 method may be unsuitable for use for the prediction of flanking noise for lightweight building constructions.

The concept of a weak sound radiating cell is proposed to reduce the low frequency radiated noise from structures. The cell consists of two coupled surfaces such that, when placed on a vibrating structure, the responses of the two surfaces are nearly out-of-phase and of equal strength over a wide frequency range. This structure response leads the cell to behave as an acoustic dipole and thus as a poor sound radiating source. The control of low frequency structurally radiated noise is then achieved by covering the structure with an array of these weak radiating cells, i.e. surface treatment. Thus, the surface treatment essentially transforms the response of the structure to that of a distributed array of dipoles yielding a low sound radiating structure. Theoretical models are developed to predict the performance of the cell. Experimental verification is performed for a single cell applied to a piston-like structure to demonstrate the concept on a simple radiating structure. The results demonstrated an overall sound power level reduction of 5.2 dB between 400-1600 Hz with maximum reductions over 30 dB at discrete frequencies. Finally, an array of weak radiating cells is experimentally applied to a more complex structure, a rectangular plate. The results of the plate experiments reveal an overall sound power level reduction of 10.2 dB between 100-1600 Hz with maximum reductions of 25 dB at discrete frequencies. These results demonstrate the potential of the weak radiating cell concept to reduce low frequency structurally radiated noise. / Master of Science

The sound insulation demands for dwellings and public building has increased over the years as the number of sound sources has grown. From the outside our homes are exposed to noise from cars, trains, airplanes, etc. Noise intrudes from our neighbours and their television and stereo equipments. Also noise from spaces for mechanical services systems tends to become more important due to increasing energy saving demands. This thesis presents new analytical models for predicting the sound reduction index of single or double plate systems. In the single plate case, a theoretical and experimental analysis of the air-borne sound transmission through a single plate is presented. The plate is assumed to be excited by a diffuse sound field and the velocity distribution of the plate is derived from the Kirchoff plate equation in the frequency domain. The resulting Fourier transform is evaluated using residue calculus and the solution is verified numerically. The analytical model is valid for a wide frequency range, both below, above and at the critical frequency. Special interest is paid to the area dependency of the sound reduction index. This technique is further expanded for the double plate case by adding another plate and an intermediate layer which is modelled as a locally reacting spring. The model is valid and continuous through both the mass-spring-mass resonance and the coincidence region. The results from the analytical models show good agreement with measured results in both the single and double plate case. A simplified model is also presented for the sound reduction index of finite size floating floors. The model is valid for two elastic plates with a resilient layer in between where the bottom plate, the load-bearing slab, is assumed to be excited with a diffuse airborne sound field. The top plate and the resilient layer compose the floating floor. The problem is solved for frequencies below, between and above the critical frequencies of the plates. Above the critical frequency of the load-bearing plate, but below that of the floating slab, the main coupling between the plates will occur at the coincidence angle of the load-bearing plate. Above the critical frequency of both plates, the main transmission will occur at the angle of coincidence of each plate. As the plates will interact, the sound insulation improvement will to some extent depend on the properties of the load-bearing slab. It is shown how the sound reduction index depends on the physical parameters and the geometry of the plates. / QC 20101101

This degree project handles acoustic measurements of the heat pump EcoAir 107, made by Enertech CTC AB. The sound from the three sound sources of the heat pump, fan, compressor and four way valve, have been measured to find out how they affect the total sound level of the product. Measures to attenuate the sound level have been developed and tested. By comparing these with the sound of the heat pump, in its original state, we have found out the measures which have best effects. The best attenuating measures came to be: taped openings and holes around the compressor space, isolating the top and the bottom of the whole construction, support of the fan bottom part and shielding of the sound source with a screen at a distance of 110 mm These measures have been tested together and an average attenuation of the total sound level with 3,9 dB have been accomplished. In the front of the fan where the continuous sound is the strongest, the attenuation was 4,7 dB. This project is meant to be used as a guide by Enertech CTC AB:s during their future developing process. / Detta examensarbete behandlar akustiska undersökningar på luftvärmepumpen EcoAir 107 från Enertech CTC AB. Ljudbilden över värmepumpens tre ljudkällor, fläkt, kompressor och fyrvägsventil, har mätts upp för att se hur dessa påverkar produktens totala ljudnivå. Åtgärder för att försöka dämpa ljudnivån har sedan tagits fram och testats. Genom att jämföra dessa med ljudbilden på värmepumpen i standardutförande har vi kommit fram till de åtgärder som fungerar bäst. De bästa dämpningsåtgärderna visade sig vara: Tejpade lister och hål runt kompressorutrymmet, isolering i tak och botten av hela konstruktionen, stadgning av fläktutrymmets bottendel och avskärmning av ljudkällan med skärm på 110 mm avstånd. Dessa åtgärder har testats tillsammans och en genomsnittlig sänkning på totala ljudnivån med 3,9 dB har åstadkommits. Fläktljudet rakt framifrån, som är det starkaste ihållande ljudet från värmepumpen, sänktes med 4,7 dB. Detta arbete är tänkt att användas som hjälp vid Enertech CTC AB:s framtida utvecklingsarbete.

<p>This degree project handles acoustic measurements of the heat pump EcoAir 107, made by Enertech CTC AB. The sound from the three sound sources of the heat pump, fan, compressor and four way valve, have been measured to find out how they affect the total sound level of the product.</p><p>Measures to attenuate the sound level have been developed and tested. By comparing these with the sound of the heat pump, in its original state, we have found out the measures which have best effects.</p><p>The best attenuating measures came to be: taped openings and holes around the compressor space, isolating the top and the bottom of the whole construction, support of the fan bottom part and shielding of the sound source with a screen at a distance of 110 mm</p><p>These measures have been tested together and an average attenuation of the total sound level with 3,9 dB have been accomplished. In the front of the fan where the continuous sound is the strongest, the attenuation was 4,7 dB.</p><p>This project is meant to be used as a guide by Enertech CTC AB:s during their future developing process.</p> / <p>Detta examensarbete behandlar akustiska undersökningar på luftvärmepumpen EcoAir 107 från Enertech CTC AB. Ljudbilden över värmepumpens tre ljudkällor, fläkt, kompressor och fyrvägsventil, har mätts upp för att se hur dessa påverkar produktens totala ljudnivå. Åtgärder för att försöka dämpa ljudnivån har sedan tagits fram och testats. Genom att jämföra dessa med ljudbilden på värmepumpen i standardutförande har vi kommit fram till de åtgärder som fungerar bäst.</p><p>De bästa dämpningsåtgärderna visade sig vara: Tejpade lister och hål runt kompressorutrymmet, isolering i tak och botten av hela konstruktionen, stadgning av fläktutrymmets bottendel och avskärmning av ljudkällan med skärm på 110 mm avstånd.</p><p>Dessa åtgärder har testats tillsammans och en genomsnittlig sänkning på totala ljudnivån med 3,9 dB har åstadkommits. Fläktljudet rakt framifrån, som är det starkaste ihållande ljudet från värmepumpen, sänktes med 4,7 dB.</p><p>Detta arbete är tänkt att användas som hjälp vid Enertech CTC AB:s framtida utvecklingsarbete.</p>

Der Beitrag geht der Frage nach, inwieweit die Parallelstellenmethode, die Friedrich Cerha in seinem weithin akzeptierten Versuch der Ergänzung des 3. Akts von Lulu anwandte, von Bergs eigener Verfahrensweise abweicht. Eine Analyse des Materials aus den Akten 1 und 2, das nach der »Spiegelachse« des Werkes (dem Interludium zwischen der ersten und zweiten Szene des zweiten Aktes) wieder aufgenommenen wird, zeigt, dass Bergs Eingriffe in die Instrumentation weit gravierender waren, als es sich Cerha gestattete. Gegenstand der Analysen sind Bergs Technik und Ästhetik der Klangvariation, insbesondere die Art und Weise, wie sich die sinkende Verlaufskurve des Dramas (nach dem Tod Dr. Schöns) in der klanglichen Gestaltung von Rückbezügen auf frühere Szenen widerspiegelt. Zum Schluss werden andere Instrumentierungsversuche des dritten Aktes seit Ablauf der Schutzfrist im Jahr 2005 zur Diskussion gestellt: die Versionen von Eberhard Kloke, David Robert Coleman und Johannes Harneit. / Berg left his second opera Lulu unfinished: most parts of the third act only exist as a reduced score (particell) with very sparse hints at orchestration. When Friedrich Cerha ventured to develop the particell into a playable version, he based his work on numerous musical correspondences between the existing material of the third act and passages of the first two acts of the opera. Whenever there was a relationship, he used the orchestration of the parallel passage. On a closer view it becomes obvious, that Cerhas procedure differs substantially from Berg’s own: The composer himself at most instances changed the orchestration, when he used musical recurrences, especially in the second half of the opera (after the interlude of the second act). Here the variants of the timbre often illustrate the demise of Lulu and her »corona«, of which the article analyses some significant examples. Finally some recent attempts to create alternatives to Cerhas orchestration, the versions of Eberhard Kloke, David Robert Coleman and Johannes Harneit, are described and discussed.

<p>This report is written on commission by WSP Acoustics. The report studies the outdoor sound levels on school yards in Stockholm. The questions given by the company to be answered was what are the actual sound levels at diffrent school yards with low traffic noise and how can you construct a facade element that reduces the sound level from the outside and meet the indoor requirements. Mesurements for four hours was done at eight schools set north and south of the city centre. The measurement period included one school break and one lunch break. The results of the measurements were that the equivalent and maximum sound level had small variations between the schools with some exceptions.The equivalent sound level was Leq 58-62 dB(A) and this shows a small variation. The school with the highest equivalent sound level of 67 dB was Maria skolan. This high level can be explained by more children on the school yard together at the same time etc. The maximum sound level was 85-89 dB(A), this if the level for Sofia skolan 82 dB was ignored. The level 85-89 dB(A) also shows a small variation. Calculations of the sound reduction index (R'w) for facade elements were also carried out for all the schools. The resulting sound reduction index for the whole facade was 34-41 dB. After assuming a 200 mm thick concrete facade for Sjöstadsskolan another calculation of building elements gives that the window have to reduce R'w 32 dB to meet the indoor requirements. In the future WSP Acoustics will use this report to choose building elements such as windows when building or rebuilding schools. It can also be used if any of the eight schools in this report needs a window changed to improve the acoustics.</p>