Perceived acoustic environments, or soundscapes, of intensive care units (ICUs) can be stressful for patients. We developed an approach to enhance ICU soundscapes with soundscape interventions. Compositions of Natural, Human, or Technological sounds were designed to establish three types of sonic ambiances: Comfortable, Pleasurable, or Stimulating. The objective was to investigate the approach's effectiveness in a real-world ICU environment. In a controlled experiment conducted in a single-patient, sound-proofed ICU room, 26 healthy participants were exposed to simulated ICU soundscapes, including patient monitor alarm sounds and mechanical ventilator sounds. Nine soundscape interventions were played via speakers. Perceived pleasantness and eventfulness of resulting soundscapes and experienced pleasure and arousal of listeners were evaluated with questionnaires. Physiological indicators of stress were measured using electrocardiograms (ECGs). Pleasurable and Stimulating interventions significantly increased perceived pleasantness and eventfulness when introduced to the simulated ICU soundscape. Comfortable interventions had no significant effect, suggesting that Pleasurable and Stimulating ambiances better aligned with participants’ needs relative to the simulated soundscape. It emphasized the need to tailor ICU interventions to the preexisting acoustic environment and sound-related needs of listeners, such as comfort, distraction or reassurance. Participants reported positive emotional states while listening to the soundscape interventions, indicative of positive listener experiences. Preliminary insights regarding changes in heartrate variability hinted that soundscape interventions could potentially contribute to reduced stress levels. The effectiveness of interventions depended on their featured sound categories, highlighting the importance of personalization. Overall, our approach was found effective, showing promise for creating listener-centric, restorative soundscapes during ICU stays.

We present a novel, to the best of our knowledge, interactive mechanism for inducing illusory rotations. Printed versions of Kitaoka’s rotating snakes illusion change effective color contrast depending on LED illumination color. This drives changes in the illusory rotations. In a psychophysical experiment, participants indicated by button press whether they perceived a given pattern to rotate as the color of illumination changed and in which direction this rotation occurred. Results could be predicted by an effective luminance contrast model, and we found high agreement between observers. This constitutes a novel manner of showing perceptual mechanisms, allowing for new applications and adding perceptual dynamics to static imagery.

This study examined how different lighting characteristics of conventional and eco-friendly lighting and environmental conditions, particularly snow cover, influenced the luminous environment and, in relation to that, pedestrian perception of faces on footpaths. The analysis was based on a dataset comprising both subjective evaluations and objective measurements. The spatial and directional light field above a footpath was measured for the two types of road lighting, of which the “eco-centric” luminaire had a lumen output of 4820 lm and reduced blue-light component (correlated color temperature (CCT) of 2200 K) compared to the conventional luminaire with 14,000 lm and 4000 K. The luminaires were analyzed under snowy and non-snowy conditions. Snow cover significantly increased light diffuseness and density (directionally averaged illuminance at a point), resulting in more uniform light and higher subjective ratings. Also, face visibility ratings were generally higher and more uniform, while non-snowy conditions led to more pronounced differences between positions and luminaire types. Regression analysis revealed that vertical illuminance at eye height was the strongest predictor of perceived facial friendliness and well-lighted-ness and contributed to more favorable ratings for the environment lighting too. The eco-centric luminaire was found to positively influence face lighting ratings but received lower ratings for environmental visibility. Increased horizontal illuminance did not consistently result in enhanced subjective evaluations, which points to limitations of traditional illuminance-based lighting standards, often considering horizontal illuminance at ground level as one of the main metrics. The “social light field” concept emphasizes a holistic approach to urban lighting design that integrates social perception and environmental sustainability by considering the distribution of the actual, resulting light throughout the urban space, especially vertical illuminance at the face and its effects on visual appearance, as well as contributing interactions with the environment and materials in it.

Terrestrial illumination undergoes continuous spectral, angular, spatial, and temporal changes throughout the day, influenced by diurnal cycles and atmospheric conditions such as haze. These variations in light exposure impact human physiology and behavior, particularly in providing "zeitgebers" (time givers) for biological rhythms. We analyzed spectral light-field data collected outdoors from dawn to dusk on four days: two in Delft (sunny and cloudy) and two overcast (uniformly cloud covered) days in Newcastle. By decomposing the light field into diffuse and directional components, we identified differences in spectral composition between these for all conditions, with overcast days showing reduced variability due to increased light scattering. Our study also explored the physiological implications for circadian regulation via melanopsin and other photoreceptors. We found that α-opic illumination vectors varied with weather, their order aligning with the sequence of photoreceptor spectral peak sensitivities—from S cones, to ipRGCs, rods, M cones, and L cones—especially under sunny and cloudy skies. Analysis of hazy versus clear images revealed that haze shifts chromaticity towards blue, potentially enhancing melanopic efficiency. Although these fluctuations are large, it is plausible that they do not impact biological rhythms to the same extent as illumination variations at dawn and dusk, ensuring that the latter remain the primary drivers of circadian rhythm regulation.

Human intervention is claimed to safeguard decision-subjects’ rights in algorithmic decision-making and contribute to their fairness perceptions. However, how decision-subjects perceive hybrid decision-maker configurations (i.e., combining humans and algorithms) is unclear. We address this gap through a mixed-methods study in an algorithmic policy enforcement context. Through qualitative interviews (Study 1; N1 = 21), we identify three characteristics (i.e., decision-maker’s profile, model type, input data provenance) that affect how decision-subjects perceive decision-makers’ ability, benevolence, and integrity (ABI). Through a quantitative study (Study 2; N2 = 223), we then systematically evaluate the individual and combined effects of these characteristics on decision-subjects’ perceptions towards decision-makers, and fairness perceptions. We found that only decision-maker’s profile contributes to perceived ability, benevolence, and integrity. Interestingly, the effect of decision-maker’s profile on fairness perceptions was mediated by perceived ability and integrity. Our findings have design implications for ensuring effective human intervention as a protection against harmful algorithmic decisions.

We studied how the characteristics of the light field, under varying real lighting conditions on footpaths at night, affect the appearance of a head-shaped light probe. A combination of physical light field measurements, image analysis, and a formal perception experiment using photographs was applied to understand how lighting characteristics affect the appearance of the face and environment. This empirical study was done in four different light configurations and for snowy and non-snowy conditions. We found that the resulting local light diffuseness, light vector, and vertical illumination correlated with the perception of friendliness, how well the faces were judged to be lit, and how comfortable the environment was rated. These local light qualities vary throughout the measured field, spatially and directionally, and showed a major effect of the presence of snow. This implies that managing and optimizing the actual light field characteristics or the spatially and directionally varying quality of the light in the three-dimensional space above the footpath is needed to fully capture its affordances such as walkability and its experiential values such as comfort in low light conditions. Extending architect Jan Gehl’s idea of the “Social field of vision”, to incorporate optical, visual, and perceptual aspects of human-centered lighting design, we propose the “The Social Light Field”.

Aims
The sound environment, or soundscape, of intensive care units (ICUs) can be stressful for patients. Soundscapes are defined as acoustic environments as perceived by people. Single-patient rooms mitigate noise, but may deprive patients of essential auditory cues. This might harm basic psychological needs, such as safety. Experiences, needs and emotions regarding soundscapes of single-patient ICU rooms remain unexplored. We aimed to understand how patients experienced these soundscapes.

Methods
This mixed-methods, single-center study involved semi-structured interviews and questionnaires five days after ICU discharge. Patients experienced the soundscapes during their ICU stay, shared experiences in interviews, and selected one to rate on need fulfilment (with a researcher-developed questionnaire), and emotions (with a validated questionnaire). Using thematic analysis, we analyzed interview transcripts by labelling sound-related experiences, sounds, and emotions.

Findings
We interviewed 26 patients. We labelled 259 sound-related experiences, 264 sounds, and 281 emotions, from which six themes emerged: Orientation through sound; Coping with disruptions; Human auditory presence; Monotony and variation; Associations and hallucinations; Communication behind closed doors. Eight patient-selected experiences involved positive emotions. Need fulfilment scores varied: scores were low for communication-related experiences, but relatively high for those involving human presence.

Conclusions
Our findings demonstrated that experiences with single-patient ICU room soundscapes can be positive or negative. For future implementation of such rooms, three insights merit consideration: positive sounds originating from corridors may be unnecessarily removed; alarms in single-patient rooms serve key supportive functions for patients; there is a lack of accessible and appropriate auditory stimulation. We recommend that these insights are taken into consideration to ensure more positive and restorative ICU stays.

Implications for Clinical Practice
In ICUs, balanced approaches that consider both positive and negative aspects of soundscapes may benefit patients in future interventions for noise mitigation. Diversifying the variety of sounds inside patient rooms could further support well-being.

We explored the underpinnings of providing positive listener experiences for intensive care unit (ICU) patients with compositions of added sounds. Our objective was to derive an approach to such interventions based on soundscape perception and need fulfillment. In one study, we gathered qualitative empirical data about imagined soundscapes where nine fundamental needs were fulfilled. Hierarchical clustering and thematic analysis showed that imagined soundscapes clustered into four types of sonic ambiances, i.e., affective connotations with soundscapes: Comfortable, Pleasurable, Motivating, or Stimulating ambiances. We derived four design parameters to achieve these ambiances with sound compositions: eventfulness, sonic ambiance qualities, narrative structure, and sound distribution. A sound artist was asked to use these parameters to create sound compositions. In a listening experiment, we examined their effects on the perceived pleasantness and eventfulness of soundscapes and on listeners' experienced pleasure and arousal. Soundscapes were perceived as pleasant with varying eventfulness in line with our structured approach. We found a strong correlation between pleasantness and with listener's pleasure and a moderate correlation between eventfulness and with listener's arousal. Finally, we suggested that in future research, three sonic ambiance types should be considered rather than four. Concluding, we showed that our need-driven approach could form a promising way to support ICU patients.

The spectral shape, irradiance, direction, and diffuseness of daylight vary regularly throughout the day. The variations in illumination and their effect on the light reflected from objects may in turn provide visual information as to the time of day. We suggest that artists' color choices for paintings of outdoor scenes might convey this information and that therefore the time of day might be decoded from the colors of paintings. Here we investigate whether human viewers' estimates of the depicted time of day in paintings correlate with their image statistics, specifically chromaticity and luminance variations. We tested time-of-day perception in 17th- to 20th-century Western European paintings via two online rating experiments. In Experiment 1, viewers' ratings from seven time choices varied significantly and largely consistently across paintings but with some ambiguity between morning and evening depictions. Analysis of the relationship between image statistics and ratings revealed correlations with the perceived time of day: higher "morningness" ratings associated with higher brightness, contrast, and saturation and darker yellow/brighter blue hues; "eveningness" with lower brightness, contrast, and saturation and darker blue/brighter yellow hues. Multiple linear regressions of extracted principal components yielded a predictive model that explained 76% of the variance in time-of-day perception. In Experiment 2, viewers rated paintings as morning or evening only; rating distributions differed significantly across paintings, and image statistics predicted people's perceptions. These results suggest that artists used different color palettes and patterns to depict different times of day, and the human visual system holds consistent assumptions about the variation of natural light depicted in paintings.

Visual perception of materials is crucial for our interactions with the world around us, and understanding the optical and perceptual mechanisms behind it has applications from spectral tuning to holistic appearance tuning. How real materials appear optically is determined by the real light they are in and described by ecological optics. With formal psychophysical experiments we test the perception of their color and texture, how matte/glossy, rough/smooth, hard/soft, glittery, velvety, etcetera we perceive them to be – and how those percepts are related to the ecological optics. I will present a series of studies into light-material-interactions and material perception of computer rendered, real, and painted materials. In addition, I will present research into effects of materials on light, and how materials can be used to make spatial and form-giving qualities of light visible in empty space, using "light probes."

We present a method to capture the 7-dimensional light field structure, and translate it into perceptually-relevant information. Our spectral cubic illumination method quantifies objective correlates of perceptually relevant diffuse and directed light components, including their variations over time, space, in color and direction, and the environment’s response to sky and sunlight. We applied it “in the wild”, capturing how light on a sunny day differs between light and shadow, and how light varies over sunny and cloudy days. We discuss the added value of our method for capturing nuanced lighting effects on scene and object appearance, such as chromatic gradients.

Research has shown that disentangling surface and illuminant colors was possible based on various scene statistics. This study investigates the statistical cues induced by the chromatic effects of interreflections. We present a numerical analysis of ambiguous spectral pairs, in which the spectral power distribution of the illuminant in one scene matched the surface reflectance function in the other scene and vice versa. If the scenes are flat or convex and perfectly matte (Lambertian), the reflected light spectra of both cases are identical. However, the incident light undergoes interreflections for concave scenes. The spectral power of interreflections will be absorbed spectrally in an exponential way, dependent on the number of interreflections. We found that this causes systematic shifts towards the spectral reflectance peaks, resulting in brightness, saturation and hue shifts. Those paired cases' color differences (CIEDE2000) are so large that humans would be able to observe them if viewed simultaneously. In addition, we find that the color shifts cause qualitatively different gradients for chromatic materials and achromatic light and vice versa. Further psychophysical testing is necessary to see whether the different color shifts for the two cases can be recognized in isolation due to material or light properties. Moreover, the light densities and light vectors are spectrally different for these cases, creating different appearances of 3D objects in non-empty rooms.

Psychological needs of users as a basis for design are at the core of design practice, yet the importance of fundamental human needs when designing soundscapes has not been studied specifically. This paper investigates the relationship between nine fundamental human needs and the affective qualities and categories of soundscapes. In a free-labeling survey study, we collected descriptions of imagined sound environments for the fulfilment of the needs, as well as ratings of the perceived affective quality of these environments. We found that needs were associated with pleasant soundscapes, while their eventfulness varied. ‘Human’ sounds were a common category for each of the nine needs considered in this study, but systematic variations of the categories were found dependent on the need. Results suggest that designing categorically different soundscapes dependent on the users’ needs will have beneficial effects.

Product lighting design is a laborious and time-consuming task. With product illustrations being increasingly rendered, the lighting challenge transferred to the virtual realm. Our approach targets lighting design in the context of a scene with fixed objects, materials, and camera parameters, illuminated by environmental lighting. Our solution offers control over the depiction of material characteristics and shape details by optimizing the illuminating environment-map. To that end, we introduce a metric that assesses the shape and material cues in terms of the designed appearance. We formalize the process and support steering the outcome using additional design constraints. We illustrate our solution with several challenging examples.

In everyday life our visual system is continuously exposedto a wide range of motionflow patterns. Our knowledgeof low-level motion processing is substantial, while higher-level processes such as future state prediction, motion con-stancy, and behavioural property estimation remain poorlyunderstood. Here, we concentrate on behavioural cues ofcollectiveflow. Collectiveflow exists of a body of individualagents that show both collective and individual behavioursfollowing a coordinated set of rules. In nature there aremany occurrences of collectiveflow on various scales, var-ious levels of complexity, across both animate and inani-mate systems (e.g., swarms of insects, cars on highways).Using a real-time browser-based simulator of a relativelysimple six-dimensional parametric model we displayed arange of collective behaviours. In a variety of experimentswith free naming, name selection, similarity judgements,and rating tasks we started exploring the parametricspace and its perceived behavioural dimensions. Wefindthat observers can name a wide range of behaviours despitethe abstraction of the simulations. Observers found thewords expressing the spacing between agents to be themost descriptive. However, in the rating experiment it wasfound to be a challenge to differentiate between more dis-tinct definitions of this spacing such as grouping or dispersal.Moreover, the six-dimensional parametric space containedmultiple instances of the same perceived behaviour, makingdirect mappings between the parametric space and percep-tual space even more complex. The challenge will be toclearly tease apart the perceived behaviours with their non-linear interactions across the explored parametric space.[This work was supported by a Marie-Skłodowska-CurieActions Individual Fellowship (H2020-MSCA-IF-2019-FLOW, Project ID: 896434) and a Marie-Skłodowska-CurieActions Innovative Training Network (MSCA-ITN-ETN,grant number 765121, 2017) DyViTo.]

Flavobacteria, which can be found in marine environments, are able to grow in highly organized colonies producing vivid iridescent colorations. While much is known about the biology of these organisms, their design potential as responsive media in user interfaces has not been explored. Our paper aims at bridging this gap by providing insights into the type, degree, and duration of change in Flavobacteria's expression, i.e., their living aesthetics. We present a tool to capture and characterize these changes concerning form, texture and iridescent color. To support the long-term study of their living aesthetics, we designed Flavorium. This bio-digital artifact provides the necessary habitat conditions for Flavobacteria to thrive for a month. Granting insights into the responsive behavior of this organism, this work presents a design space, vocabulary, and application concepts to inspire HCI and design scholars to investigate the complex temporal qualities of living media for future user interfaces.

Chromatic properties of the effective light in a space are hard to predict, measure and visualise. This is due to complex interactions between materials and illuminants. Here, we describe, measure and visualise the effects of inter-reflections on the structure of the physical light field for diffusely scattering scenes. The spectral properties of inter-reflections vary as a function of the number of bounces they went through. Via a computational model, these spectral variations were found to be systematic and correspond with brightness, saturation and hue shifts. We extended our light-field methods to measure and understand these spectral effects on the first-order properties of light fields, the light density and light vector. We tested the model via a set of computer renderings and cubic spectral illuminance measurements in mock-up rooms under different furnishing scenarios for two types of illuminants. The predicted spectral variations were confirmed and indeed varied systematically within the resulting light field, spatially and directionally. Inter-reflections predominantly affect the light density spectrum and have less impact on the light vector spectrum. It is important to consider these differential effects for their consequences on the colour rendering of 3-dimensional objects and people.

In everyday scenes, the effective light (the actual light in a space) can be defined as a complex light field, resulting from a mixture of emissive light sources and indirect mutual surface (inter-)reflections. Hence, the light field typically consists of diffuse and directional illumination and varies in spectral irradiance as a function of location and direction. The spatially varying differences between the diffuse and directional illumination spectra induce correlated colour temperature (CCT) and colour rendition variations over the light fields. Here, we aim to investigate the colourimetric properties of the actual light, termed the effective CCT and colour rendition, for spaces of one reflectance (uni-chromatic spaces). The spectra of the diffuse light-field component (light density) and the directional light-field component (light vector) were measured in both physical and simulated uni-chromatic spaces illuminated by ordinary white light sources. We empirically tested the effective CCT and colour rendition for the light density and the light vector, separately. There were significant differences between the lamp-specified CCT and colour rendition and the actual light-based effective CCT and effective colour rendition. Inter-reflections predominantly affected the CCT and colour rendition of the light density relative to the light vector. Treating the diffuse and directional light-field components in a linear model reveals the separate influences of the light source and scene. These effects show the importance of a 3D version of colour checkers for lighting designers, architects or in general computer graphics applications, for which we propose simple Lambertian spheres.

In natural scenes, the wavelength-dependent sunlight scattering in the atmosphere and the presence of occluders and mutual reflections cause variations in the local illumination's magnitude, direction, and spectral composition as a function of time and space. Yet, unlike the characterization of temporal changes of natural light, these spatial variations have received relatively limited attention. In this paper, we employed the light field concept to quantify those variations and empirically demonstrated that they are significant and how the different contributions of the diffuse and directed parts can be measured.