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Senast publicerade

1 D Aftertreatment Simulation and Model Calibration for Euro VII Engines
(2026) Dennis, Wang
Management of a ground-borne noise prediction methodology for railway traffic in tunnels
(2026) Höjdefors, Carl
The purpose of this thesis was to understand how a new prediction methodology for ground-borne noise should be maintained and continuously updated. The scope included ground-borne noise from trains in tunnels and focused on the predictions to fulfill the requirements for the post-construction phase. Research questions were formulated and they were as follows: What new data should be added to the methodology? What are the risks when managing the methodology? What strategy should be used to ensure a successful management? The method was composed of a literature review, case studies, interviews and a numerical analysis. In total, 22 respondents were interviewed. The results from the case studies demonstrated that under-ballast mats are common and that assumptions related to the foundation differ between projects. However, assumptions used when obtaining the ground-borne noise level in a room are similar. In Sweden, the same noise criteria have been utilized in practice. The results from the interview sessions demonstrated that more information regarding the coupling between the tunnel and the building is needed. Also, the contribution from railway components can be added to the implemented model. Measures should not be added to the implemented model since it could alter the creativity during development. However, a default value for an under-ballast mat can be added. Advantages with the methodology is that it contains a great deal of data, a detailed literature study, includes the uncertainties and that it is transparent. The source strength in the model was developed using data from two specific tunnels. One identified risk is that the model might not make sufficient predictions for cases with significantly different conditions. Another risk is that it stagnates when it is no longer maintained. To ensure a successful management, a reference group is needed that can discuss it. The process of using the methodology and the implementation of the model should be further explained in a step-by-step user guide. New measurements are required and results from other methods, such as specific transfer functions can be used. The numerical part demonstrated for a specific case that no measures on the track are needed for dwellings situated further than 100 m away from the tunnel when passenger trains are investigated. For freight trains, the same distance must exceed 200 m. A difference of 5 dBA exists between results from the implemented model and results from the EIA (Environmental Impact Assessment) in the Lärketorpet project. Important for fulfilling the criteria is that an upgraded rail structure is used. This will mitigate the ground-borne noise levels. Future studies could focus on comparing numerical results from other projects and investigate ground-borne noise in the construction phase.
Iterative Partial Tracking in Inharmonic Audio Signals; Expanding the YIN Algorithm for Real-Time Monitoring and Treatment of Drum Harmonics
(2026) Fährlin, Alva
Time-domain subtraction of partials allows for lossless amplitude scaling of an in put signal’s tonal components, without affecting the phase. A method for real-time partial tracking in inharmonic transient audio signals, such as drum recordings, was developed by adapting the YIN algorithm [1] and combining it with time-domain subtraction of synthesised sinusoids. The algorithm can be applied block-wise to any tonal audio signal with analysis blocks as short as two times the period of the fundamental frequency of the signal, and step sizes shorter than the typical looka head of a DAW. This allows for real-time application of the algorithm in a DAW, detecting fundamental frequencies down to at least 60 Hz. The study features an overview of three methods for partial- and fundamental fre quency estimation: lag domain methods, spectral methods, and transient modelling synthesis. Based on the overview, a new method called Iterative Partial Tracking (IPT) was formulated, in order to track partials via fundamental frequency detec tion alone. A YIN-based IPT implementation was adapted to the requirements set by DAW applicability, and tested on a set of floor tom recordings. The results were found to be promising: up to four partials were estimated in a typical floor tom with a gross pitch error (GPE) of 0%. The fundamental frequency of a floor tom was, in some recordings, estimated with errors that never exceeded one semitone. The accuracy of higher-order partial estimations could be improved by applying shorter, frequency based, analysis frame lengths, and the validation procedure of frequency estimations is subject to further improvements. But in its foundation, the lag-domain approach to tracking partials in inharmonic audio signals seems like a promising method, possible to implement in real-time applications where tonal atonal signal separation is required.
Perceptual Assessment of Loudspeaker Performance; A Comparison of In-Situ and Binaural Evaluation Methods
(2026) Li, Minghui; Xin, Su
In practical industrial scenarios, conducting in-situ listening evaluations is often difficult due to limitations in environment and experimental conditions. As a result, recorded audio is frequently used as an alternative for subjective loudspeaker evaluation, although its perceptual validity remains unclear. This study investigates whether simplified binaural recordings can preserve subjective loud speaker evaluation trends observed under direct listening conditions. Subjective listening experiments were conducted using three loudspeakers with different spectral characteristics and four representative audio signals under both in-situ listening and binaural playback conditions. Pairwise comparison and ranking analyses were used to evaluate perceptual consistency between the two listening conditions. The results show that binaural playback was generally able to preserve the subjective evaluation trends observed in direct listening experiments, particularly for bass and music signals. Additional experiments under background noise conditions further demonstrated that perceptual discriminability between loudspeakers decreased as noise level increased. Based on the validated binaural recordings, this study further proposed several spectral perceptual models linking spectral characteristics with subjective perception. Model-guided spectral modification experiments showed that the predicted perceptual tendencies were generally consistent with listeners’ evaluations. Overall, the results suggest that simplified binaural recordings can preserve perceptually relevant loudspeaker information to a considerable extent and may provide a practical alternative to large-scale in-situ listening tests during loudspeaker evaluation and design.
Modelling Underwater Sound Propagation Using the Finite-Difference Time-Domain Method
(2026) Cunningham, Callum
Marine life in coastal regions is under environmental pressure from anthropogenic activities such as commercial shipping, offshore wind farms and leisure boats. As part of an ongoing research project to create underwater noise maps for recreational boats, IVL Swedish Environmental Research Institute has measured propagation loss in Kosterhavet marine protected area. These measurements show a variety of acoustic effects that are not captured by simple analytical models. The goal of this project is to produce a numerical model that can provide a more detailed understanding of how noise propagates underwater to the surrounding environment. A three-dimensional finite-difference time-domain (FDTD) model was developed in MATLAB. The model was validated by comparison to known analytical solutions of increasing complexity. First, it was confirmed that the model reproduces propagation loss due to spherical spreading, agreeing closely with analytical predictions. A nearly perfectly matched layer (NPML) was implemented to avoid unwanted reflections from the boundaries of a truncated domain. The decay factor and layer width were optimised empirically, achieving reduction of reflected wave energy up to 45 dB relative to a rigid boundary condition. Then, several boundary conditions were tested including a rigid wall boundary, a pressure-release condition and a finite-impedance boundary, with the latter two conditions representing the water-air interface and the water-seabed interface respectively. Analytical solutions for each case were calculated and show strong agreement with model output in both frequency and time domains. Finally, an attempt was made to reproduce real world measurements of propagation loss provided by IVL using different configurations of sea floor properties. Initial results show promise however require further investigation and fine-tuning of the model to accurately reproduce measurements.