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Is This Data Point In your Training Set? Similarity-based Inference Attacks: Performance Evaluation of Range Membership Attacks to Audit Privacy Risks in Machine Learning Models

(2025) Nawrin Nova, Sifat; Shubham, Saha

Membership Inference Attacks (MIAs) pose a serious threat to the privacy of machine learning (ML) models by determining whether a specific data point was used during model training. A recent and powerful variant, the Range Membership Inference Attack (RaMIA), assesses privacy risks over a range of semantically similar data points. However, its practical application is limited by a high query overhead, as it requires querying the target model for every sample in the range. This thesis proposes and evaluates a novel approach designed to overcome this limitation by combining range queries with group testing principles to reduce the number of queries sent to the target model without losing the attack performance and making the attack more stealthy. Instead of testing every sample, this method first groups similar data points based on their extracted features and then queries only a small number of strategically chosen representatives. All the experiments are conducted on the CIFAR-10 dataset, comparing its performance against the standard RaMIA baseline. The results demonstrate that RaMIA with group testing successfully reduces the number of queries by 84% in a setting of 50 augmentations. This work reveals that even minor enhancements in query design and decoding strategy can lead to substantial gains in auditing. Moreover, we provide practical recommendations for tuning key hyperparameters and integrate our attack into the LeakPro framework for reproducibility and broader adoption in privacy auditing of ML models.

Field measurements of airborne sound insulation; Differences in results for methods prescribed in current standards at different degrees of furnishing and a possible new approach

(2025) von Schmalensee, Marcus

There is a widespread belief among acousticians that the airborne sound insulation measured between empty rooms systematically results in lower values than when furnished. No studies investigating the phenomenon were found and since inspection measurements are mostly performed in empty rooms, the difference, if it exists, would need to be quantified and addressed. Since regulations in Sweden, in many cases, require measurements down to lower frequencies than in other countries, and the theoretical framework on which existing methods are based is generally less valid at lower frequencies, there is reason to believe that the problem could be more common in Sweden. In addition, a variety of measurement methods are described in current standards, of which only a few are regularly used. No studies have been found where the methods are systematically tested and compared. Methods based on measurements and further processing of impulse responses, using deterministic signals, are very useful in certain situations but are, to the author’s knowledge, almost never used. This is probably mainly because methods based on manual scanning paths with a hand-held analyzer are more time-efficient in field measurements. The main objective of this study is to identify whether furnishing leads to systematic deviations in measured sound insulation. This is achieved by testing and comparing several of the methods described in the current standards. A possible explanation for the error could be that the sound pressure levels are measured with the loudspeaker positioned in the source room, while the reverberation times are measured with the loudspeaker in the receiving room. There is reason to believe that the differences in the sound fields for these two cases reduce the compatibility between these measurements, especially at low frequencies. Since methods based on impulse responses measured with swept-sine signals provide superior signal-to-noise ratios that far exceed the other methods, the reverberation time can possibly be measured without moving the loudspeaker from the source to the receiving room. If that would be possible, both the sound level differences between the rooms and the reverberation time, i.e. all measurements required to evaluate the sound insulation, could be measured from a single sine sweep. If a foldable measurement stand was developed, which quickly could spread out a number of microphone positions in a space, field measurement times could be drastically reduced. However, the method where the reverberation time is measured with the loudspeaker in the source room was shown to perform significantly worse than default methods. Nevertheless, the method can potentially be used for simpler survey measurements, without further development. Systematic differences, between furnished unfurnished rooms, were demonstrated for the weighted standardized level differences. However, contrary to what was expected, the differences do not arise as a result of deviations for the lower 1/3-octave bands. Rather, the differences arise as a result of deviations for the 1/3-octave bands 200 Hz, 250 Hz and for some higher frequency bands. Hence, the results do not support the suspicion that measurements according to the Swedish regulations, which includes frequency bands below 100 Hz, result in systematic deviations greater than what would be the case in other countries.

Acoustic Source Localization for an Indoor Pass-By Measurement System; A Beamforming Approach Using a One-Dimensional Sparse Microphone Array

(2025) Seger, Gustav; Sehic, Semir

Accurate source localization of acoustic sources is critical for vehicle noise analysis. This thesis examines the possibility of using sparse microphone arrays, which are part of an indoor pass-by measurement rig, as acoustic cameras in a near-field scenario. Four different techniques were implemented, validated and comparatively analysed. Three beamforming techniques, Delay and Sum (DS), Minimum Variance Distortionless Response (MVDR) and Functional Beamforming (FBF). The fourth technique is a post-processing algorithm, A Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS). Each technique was evaluated based on spatial resolution, robustness to noise, array element imperfections and performance on real measurement data. The DS beamformer demonstrated robustness to array element sensitivity variations and placement errors, but was limited under low Signal-to-Noise Ratio (SNR) conditions due to its broad mainlobe and elevated side-lobe levels. MVDR and FBF, both implemented using Cross Spectral Matrices (CSM), offered improved directional accuracy and noise suppression capabilities. FBF introduced a tunable order factor which enhances control of side-lobe suppression and mainlobe width, making it particularly useful as a pre-processing step for DAMAS. The DAMAS algorithm was implemented as a post-beamforming processing tool, offering improved spatial resolution, although its performance was based heavily on the quality of the beamformer input. Validation included both simulations and real measurements conducted inside a semi-anechoic pass-by test rig, using stationary vehicle signals. All techniques successfully localized tonal sources across a frequency range of 40 − 1600 Hz. However, the spatial resolution remained constrained by array aperture size and wavelength. Ground reflections introduced interference patterns that reduced accuracy at certain frequencies, mimicking the acoustic behaviour expected in a road-like environment. The thesis concludes that combining MVDR and FBF for initial localization and DAMAS for source separation provides a flexible approach for acoustic source localization. The importance of accurate propagation and time delay modelling, calibration and signal processing was highlighted as a key factor to achieving reliable beamforming results in vehicle acoustic pass-by measurements

Planering för rekreation i förtätningsprojekt; möjligheter och utmaningar för rekreationsytor utifrån kvalitet, kapacitet och tillgänglighet vid Masthuggskajen i Göteborg

(2025) Larsson, Sofie; Wallén, Sara

I takt med att städer växer och förtätas blir ytan för rekreation alltmer begränsad. Rekreationsytor såsom parker, grönområden och stråk fyller en central funktion för människors psykiska och fysiska hälsa samt för stadens klimatmässiga och sociala hållbarhet. I förtätningsprojekt blir dessa ytor allt svårare att planera in samtidigt som de behöver hålla en hög kvalitet och vara tillgängliga för många. Rekreation i stadsrum beskrivs som en viktig faktor för att skapa inkluderande, trygga och levande stadsmiljöer. Syftet med rapporten är att belysa möjligheter och utmaningar i planeringen av kvalitativa rekreationsytor i förtätningsprojekt, i en fallstudie av Masthuggskajen i Göteborg. Genom en kombination av litteraturstudie, GIS-analyser, intervjuer och fallstudie analyseras tre olika rekreationsytor i området utifrån kvalitativa och kvantitativa aspekter med särskild hänsyn till projektets hållbarhetsmål. Arbetet bygger på forskningsbaserade begrepp som upplevelsevärden och teorin om aktiv och passiv rekreation samt etablerade riktlinjer för grönstrukturens utformning i den täta staden. Resultatet visar att området präglas av god ambition att skapa inkluderande och mångfunktionella stadsrum där kvalitet och tillgänglighet till de rekreativa ytorna anses hög. Samtidigt finns det utmaningar kopplat till kapacitet och jämlik tillgång såväl som brist på återhämtande kvaliteter. Parkernas ytor riskerar att bli begränsade i relation till det antal människor som förväntas bo, arbeta och röra sig i området. Genom analysen framkommer även att det finns en medvetenhet om att integrera olika upplevelsevärden i planeringen vilket stärker områdets sociala funktioner och rekreationsmöjligheter. Studien visar på vikten av att arbeta platsmedvetet i planeringen av rekreationsytor där kvalitativa och kvantitativa aspekter i samspel med tillgänglighet, integreras tidigt i utformningen.

Renaturalization factory; participatory fabrication of nature

(2025) Johansson, Julia

As a result of rapid urbanization certain challenges have increased such as environmental pressure and social exclusion. This calls for sustainable ways of dealing with continuous city expansion. Evenemangsområdet is at the center of discussions about how Gothenburg should expand but the municipality’s proposal has been critiqued not least because of its exclusive process and its ignorance towards local ecological values. The objective of this thesis is to explore possible futures for a site within Evenemangsområdet by speculating about how that site could become renaturalized through citizen engagement. The site is currently underused, both from a human and nonhuman perspective, meaning that it provides little value to either group. The research is qualitative and partially speculative. Through a case study analysis, mapping of opportunities, and speculative design, the thesis focuses on social and ecological sustainability, and alternative tools for urban designers through the following themes: human and nonhuman actors, temporary activation, disruptive architecture, wilderness, renaturalization, speculation, scenario, prototyping, participation, and alternative mapping. The site analysis focuses on social, cultural and ecological aspects and makes out the foundation for the speculative design proposal that follows. It focuses on the two local assets that frame the site: Stora Katrinelund landeri and Mölndalsån. The thesis results in a speculative design proposal of a temporary activation project – the Renaturalization Factory. With a common mission to renaturalize the site, people could mobilize around the Garden Cart, a prototype that facilitates collective gardening. The goal of the factory is to convert asphalted areas into a renaturalized landscape. The activation would be the operation of the factory. As the Anthropocene makes itself heard through climate disasters around the world, it seems as if more people come to realize the urgency of the situation. Through the activistic and disruptive activity of breaking up asphalt to plant seeds of future ecological resistance, the Renaturalization Factory engages those who are scared, angry and hopeful. Those who see the site as a site of opportunities. This thesis is a statement to move more radically towards ecologically and socially sustainable urban practice.