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Theory and measurement of low-frequency structure-borne sound in concrete buildings
(2024) Cheng, Jiali
Low-frequency structure-borne sound is a critical issue because this type of noise travels long distances with little attenuation. This has become a growing concern with the advancement of audio technology and loudspeakers. It is especially problematic in spaces like home theatres and concert halls, where it can cause discomfort and long-term health effects for residents, even those located at a distance. Therefore, predicting effective sound insulation in the early building design process is essential. This thesis investigates the behaviour of low-frequency vibrations in a concrete floor within an office building, focusing on the relationship between the propagation speed of bending waves, the loss factor, and the attenuation of vibrations over distance. It is built on the work of Østvik1, who described the correlation between structural reverberation and distance-dependent damping of vibrations of a concrete slab within a building. A theoretical model of vibration decay, based on the propagation speed and the loss factor of the structure, was proposed and validated through vibration measurements. These measurements were conducted at multiple excitation points on both the floor and the wall, with results confirming that the propagation speed of bending waves follows the expected square-root dependence on frequency. A lower propagation speed was observed when the floor was excited on the wall, compared to direct excitations on the floor. The level decay predicted by the model generally followed a logarithmic pattern, with geometric spreading being dominant. More significant decay was observed at higher frequencies than at lower ones. Furthermore, the structural reverberation time was found to decrease with increasing frequency, indicating that the vibrations last longer at low frequencies. The total loss factor also decreased with increasing frequency, suggesting that energy loss per oscillation is greater at low frequencies. These findings provide valuable insights into lowfrequency vibration propagation. Further research with additional excitation and measurement positions is needed to validate the proposed relationship and better understand the variations observed in this study.
Flanking sound transmission over CLT-joints
(2024) Andersson, Eric
Cross-laminated timber (CLT) is a sustainable and efficient building material that has gained popularity due to its high stiffness, low density, and reduced environmental impact. However, predicting low-frequency sound and vibration transmission across CLT joints remains a significant challenge. This thesis focuses on improving the modeling of flanking sound transmission over different CLT joint configurations, using finite element modeling (FEM) validated through experimental measurements. The study involves measurements of vibration reduction index (Kij) for undamped and isolated joint setups. The FEM simulations closely matched experimental trends for non isolated setups, though some discrepancies arose due to possible differences in coupling conditions and measurement resolution. In isolated setups, FEM predictions highlighted limitations in accurately simulating the effect of vibration-isolation brackets, particularly in representing their behavior when fastened to the CLT panels. The results emphasize the need for refined FEM approaches to better model the dynamic behavior of joints and connections in CLT structures. Future work should focus on enhancing joint coupling simulations, modeling of vibration-isolation brackets and optimizing experimental setups to achieve free boundary conditions. Thereby advancing the acoustic performance prediction for CLT constructions.
Gradient descent based adaptive IIR filtering with direct and lattice form filter structures; applied to estimation of a headphone compensation filter and binaural head related transfer functions
(2025) Lendon, Alexander
In acoustic Digital Signal Processing (DSP), Finite Impulse Response (FIR) filters are commonly used due to their stability and ease of design. However, Infinite Impulse Response (IIR) filters offer better frequency resolution at lower filter orders, making them ideal for hardware-constrained applications like portable AR/VR headsets. With advances in computational methods, optimising IIR filters has become straightforward, making it important to compare their performance against traditional FIR filters. This thesis investigates adaptive IIR filtering algorithms using Gradient Descent (GD) methods, applied to both direct form and lattice form filter structures. Lattice form filter structures provide the benefit of an in-built stability test which can guarantee that the produced IIR filter remains stable at each step. This is essential for reliable IIR filter design and allows for further modifications to the optimisation routine. For the studies, the Modified GD direct form and the Simplified Partial Gradient Descent (SPGD) lattice form algorithms were used to model a headphone compensation filter and binaural Head-Related Transfer Function (HRTF), comparing the resulting IIR filters to equivalent FIR filters. Parameter studies on step-size coefficient and filter order were conducted to assess accuracy in both frequency and time domain. The study found that both IIR filter forms reduced order length to 20% of the HRTF filter order and 40% of the compensation filter order, both within a 1 dB accuracy threshold in the magnitude response. This results in reduction in numerical operations of 60% for the HRTF filter and 20% for the headphone compensation filter. This work demonstrates the that significant order reduction is possible using lattice form, gradient decent based adaptive filters. The exact reduction depends on the target filter and requires similar simulations and analysis to those used here.
Enhancing project management and inspection efficiency through advanced data integration in construction projects
(2024) Ali, Isaac; Shahul Hameed, Ashiq Ahmed
The construction industry is increasingly adopting advanced digital tools to enhance project management practices, improve data accuracy, and streamline communication. This master’s thesis investigates the integration of StreamBIM, a Building Information Modeling (BIM) software, with Power BI, a powerful data visualization and analytics tool, to enhance project management within the construction industry. The study focuses on a real-world project exploring the benefits and challenges associated with this technological integration. Through a detailed case study approach, including semistructured interviews and thorough document analysis, the research identifies significant improvements in data management, inspection protocols, and overall project efficiency. The integration allows for advanced data filtering, customized visual representations, and the creation of interactive dashboards, which enhance the ability to monitor progress, identify issues, and make informed decisions. Key findings demonstrate that this integration not only improves the accuracy and timeliness of data but also facilitates better communication and collaboration among project stakeholders. The results highlight the transformative impact of integrating StreamBIM with Power BI, showing marked enhancements in the preparation and planning stages of inspections, standardization and automation of reporting processes, and overall quality control. The study concludes with recommendations for further improving digital tools in construction management, emphasizing the need for comprehensive training programs and the adoption of a model-based construction approach to fully leverage the capabilities of BIM and data visualization technologies. This research contributes to the body of knowledge on BIM integration, offering practical insights and solutions for industry professionals aiming to achieve more efficient and effective project management outcomes.
Total BIM in Swedish installation contracting; a comparative study of model-based and traditional ventilation contracting
(2024) Ahmadi, Reza
Time waste and budget overruns are common issues in most construction projects. Digital tools like Building Information Modeling (BIM) have been developed to address these problems. While BIM has improved the design process, its adoption on construction sites remains limited, where paper drawings are still dominant. Total BIM is a new concept that is becoming popular in Scandinavia and aims to use BIM models even in the production phase. This approach eliminates the need for paper drawings and has the potential to improve both project efficiency and accuracy. Therefore, this study aims to compare model-based versus traditional working methods in the production phase of a real-world installation project and analyze workers' reactions to the new concept. To conduct this comparison, the traditional workflows of an installation company were studied, and one of their ongoing ventilation projects, Blå Stjärnan, was selected as the reference project. A 3D model of the project was compiled using StreamBIM, and the company’s installers formed the study group. The comparison focused on three key areas: time spent on quantity takeoff, differences in cost estimation, and the workers’ experience with the installation process. The study also identifies several lessons and challenges related to the implementation of Total BIM. The results showed that model-based quantity takeoff improved efficiency by 40 times compared to traditional drawing-based methods. Additionally, traditional methods tended to underestimate project costs by 8% due to human errors. Workers on-site reported significant improvements in planning, efficiency, and accuracy when using the 3D model, and noted that communication through the model would have been beneficial if requirements were set. However, despite its potential, the industry remains hesitant to fully adopt Total BIM due to established workflows and the legal binding nature of paper drawings. Increased knowledge within the construction industry and successful real-world implementations could encourage clients to oblige the use of BIM models in production.