Indoor Soundscape Research Articles

Systematic review of indoor soundscape assessments: Activity-based psycho-acoustics analysis

This study examines 22 peer-reviewed papers to offer insights into the current utilization of psycho-acoustic sound quality metrics in research focused on indoor soundscapes. The selection of papers followed the PRISMA method for systematic review, followed by descriptive and bibliometric analyses. The review focuses on (i) identifying what psycho-acoustic indicators can be utilized to obtain an objective soundscape assessment, and (ii) determining if soundscape descriptors vary with the desired activities within the indoor space. The findings provide an overview of how psycho-acoustic sound quality metrics are used to predict perceived annoyance in indoor environments. The discussion delves into response variables related to occupants’ sound perception across various indoor settings. It highlights the lack of sufficient research on prediction models based on psycho-acoustic sound quality metrics within indoor soundscapes. Further research is required to develop tools enabling the optimal design of indoor soundscapes, which can vary according to the intended use of the room.

Office soundscape assessment: A model of acoustic environment perception in open-plan officesa).

The soundscape approach has been utilised in recent research for residential environments, but applications to indoor working environments remain limited. This study investigated the suitability of affective quality evaluations of open-plan office acoustics. Perceptual assessments were completed by occupants of eight open-plan office floorplates, using affective dimensions outlined in PD ISO/TS 12913-3:2019 and indoor soundscape studies. Participant demographic, contextual, work-related quality, and psychological well-being data were collected. Workstation noise levels were measured following BS ISO 22955:2021. Principal component analysis identified Pleasantness, Eventfulness, and Emptiness as the main perceptual dimensions, cumulatively explaining 56% of the total variance. Results indicate the suitability of the PD ISO/TS 12913-3:2019 two-dimensional model for open-plan offices. The perceived presence of human sounds negatively correlated with ISO Pleasantness yet positively correlated with ISO Eventfulness. Participant gender and aural diversity mediated ISO Pleasantness. Psychological well-being and work-related quality correlated positively with soundscape pleasantness. No correlations were found between level-based acoustical indicators-equivalent continuous sound level (LAeq), level exceeded 10% (LA10) and 90% (LA90) of the time, level variability (LA10-LA90) and Liveliness-and perceptual scores. A conceptual representation of open-plan office soundscape perception is presented, offering a framework for evaluating and designing workspaces to enhance well-being.

Psychoacoustic metrics and affective responses in indoor soundscapes: Implications for restorative soundscapes

This study investigates the links between psychoacoustic metrics and affective responses in indoor soundscapes, guided by the ISO/TS 12913 standard. Through the analysis of an indoor soundscapes dataset, we examine how various psychoacoustic metrics, namely sharpness (S), fluctuation strength (FS), and roughness (R), influence affective responses such as pleasant and eventful. Our research reveals that eventful and annoying soundscapes show higher values of (S), (FS), and (R). Conversely, pleasant soundscapes tend to show lower values in these metrics. The findings suggest that while these metrics can be effective in designing eventful soundscapes, they may be less useful for creating pleasant acoustic environments. This study contributes to the understanding of the applicability of current psychoacoustic metrics for the type of soundscape intervention and calls for the development of new psychoacoustic metrics to design restorative soundscapes that enhance well-being.

Assessing the indoor soundscape approach among university students' home study places

University students spend a considerable time at study places. The acoustical quality of these study places is one of the indoor environmental qualities (IEQ) that can have an impact on student's health, comfort, and performance. The indoor soundscape approach has been introduced to better understand occupants' sound perception and experience of sounds in relation to the environment. This study aims to explore the indoor soundscapes of home study places of these students by conducting semi-structured interviews with 23 university students with different profiles. For qualitative analysis, open coding was used. Sub-categories, based on the codes, and categories were created and assigned to the soundscape themes that are defined in ISO 12913-1. An affinity diagram consisting of the themes, categories, and sub-categories was initially developed. Then, it was validated through two workshops with participants. The results showed that the interpretation of the sound environment, responses, and outcomes differed among the students. In a previous study, 451 students were clustered in 5 clusters with similar acoustical preferences (profiles). Therefore, it is recommended to consider making the indoor soundscape approach applicable for different profiles of occupants.

Investigation of perceived annoyance in indoor workplaces using short and ultra-short sound samples

Typically, metrics crucial for assessing sound quality are derived from high-quality audio samples obtained in controlled environments. However, due to the sensitive nature of workplace settings, recording audio samples on-site becomes impractical. Privacy emerges as a significant concern for all when collecting audio samples. Consequently, best practice would require that all analyses must occur either locally on a device used to record audio or in the cloud, utilizing a purely mathematical approach. The paper aims to formulate methodologies for determining psycho-acoustic sound quality metrics without the need to analyze audio data directly. This can be achieved by collecting and analyzing data in small batches. The variation of these metrics over these smaller samples can serve as an indicator of sound quality. Initiating the determination of values for psycho-acoustic sound quality metrics such as loudness (N), sharpness (S), roughness (R) and fluctuation strength (FS) in short and ultra-short batches, followed by monitoring their variation over an extended period (e.g., 5 minutes), provides additional insight into the sound characteristics of the space. Using the obtained psycho-acoustic sound quality metrics, we will explore the perceived annoyance among occupants through indoor soundscape assessments.

Predicting real indoor soundscapes based on auditory and non-auditory factors across different loudness ranges with linear and nonlinear models

Studies on the indoor sound environment have mainly focused on the impact of traffic, neighbor, or ventilation noise on health, annoyance, or sound quality. When conducting such studies in the laboratory, acoustic stimuli are often tailored to the research question, which presumably do not reflect the variation in the acoustic environment at home. Thus, we re-analyzed soundscape data gathered by participants at their homes several times a day. Since the recorded soundscapes differed notably between participants (and their dwellings) in terms of loudness, we investigated if cross-validated linear regression and Random Forest models predicting the soundscape dimensions based on four loudness quartile subsets achieve higher prediction performance compared to models using the full volume range. Our results, which are based on the explanation of the variance in the targets, the correlation between the targets and acoustic and perceptual predictors, and the predictor importance, suggest the use of Random Forest models based on the entire loudness range. In our analysis of predictor importance, Pleasantness was understandably dominated by perceptual measures, whereas Eventfulness was driven through acoustic and psychoacoustic predictors. Interestingly, all models based on quiet soundscapes behaved differently, which provides scope for investigating the underlying causes in future.

Virtual reality application to explore indoor soundscape and physiological responses to audio-visual biophilic design interventions: An experimental study in an office environment

Among the major sources of disturbance in offices, noise and poor acoustics consistently rank at the top. Moreover, the positive impact which connecting with nature has on individuals is well-documented, yet still not investigated in-depth in terms of office soundscapes. In the present study, a methodology using Virtual Reality (VR) technology is employed to analyse the benefits of Biophilic Design interventions in office spaces. Notably, the study investigates the independent and interaction effects of audio-visual connection with nature on 1) office soundscape, and 2) physiological parameters, and 3) explores potential correlations between physiological and soundscape response. Three different visual scenarios (Indoor Green, Outdoor Green and Non-Biophilic) and three sound environments (Office − O, Office + Traffic − O + T and Office + Nature − O + N) for a virtual office environment were combined in a between-subjects design experiment. During their exposure to each acoustical scenario, 198 participants’ responses on perceived affective quality of soundscapes (ISO/TS 12913-2) and physiological reactions (Electro-Dermal Activity - EDA, Pulse Rate - PR, Skin Temperature -ST) were collected. The results show a major effect of the sound factor on soundscape assessment, with the O + N scenario resulting in increased pleasantness and eventfulness compared to the O scenario, i.e. a more vibrant office soundscape. Moreover, an interaction between sound and visual stimuli on pleasantness was detected, with IG being more effective in O + N, while OG being more beneficial in the O + T scenario. Significant positive physiological responses were more elicited in the presence of an acoustical connection with nature than a visual one: pleasant soundscapes of nature were associated with lowered EDA and PR with an additional improvement in EDA in the presence of indoor greenery. Moreover, a more pleasant sound (O + N) tended to decrease skin temperature in the presence of indoor greenery, while a more unpleasant and eventful acoustical scenario (O + T) gave the largest PR increase in the absence of nature-related elements indoors. This research provides first insights for the biophilic design of office spaces through nature-related audio-visual stimuli.

Reducing noise with augmented reality in indoor soundscapes

Noise pollution has a significant impact on quality of life. In indoor soundscapes like open offices, noise exposure creates stress that leads to reduced performance, provokes annoyance and changes in social behaviour. The ReNAR project aims at studying two augmented reality approaches, targeted towards additional sound sources which levels are below or equal to the noise sources ones The first approach tend to conceal the presence of unpleasant sources by adding some spectro-temporal cues which will seemingly convert it into a more pleasant one. Adversarial machine learning techniques will be considered to learn correspondences between noise and pleasing sounds and to train a deep audio synthesiser able to generate an effective concealing sound of moderate loudness. The second approach tend to tackle a common issue encountered in open offices, where the ability to concentrate on the task at hand is made harder when people are speaking nearby. We propose to reduce the intelligibility of nearby speech by the addition of sound sources whose spectro-temporal properties are specifically designed or synthesised with a generative model to conceal important aspects of the nearby speech. The formal position, general frame and expected outcomes of the project will be developed and discussed.

Indoor soundscape design of autonomous vehicles that comprehensively applies acoustic characteristics of architectural space type

According to the paradigm shift in the indoor space design of future autonomous vehicles, the indoor space of the vehicle was classified according to the purpose of use and the optimal soundscape design for each type was proposed. The vehicle selected for the measurement can be the basic type of future autonomous vehicles, a relatively wide van suitable for building space investigation, and the space target was selected as spaces for listening to music, working (meeting), and resting. Accordingly, for the soundscape design, an audible sound source was produced and used for evaluation by conducting a sound field survey and computer simulation inside the vehicle. The indoor soundscape of the vehicle was evaluated by providing binaural sound source in the auditory test environment. The evaluation indicators were selected based on the indoor soundscape parameters in the architectural spaces such as concert halls and office buildings.

Emotional response to natural and artificial sound and indoor sound scape in residential space

The demand for effective ways to alleviate stress caused by residential noise is growing. To better understand individual preferences and strategies for reducing noise-induced stress, a laboratory experiment was conducted to classify emotional responses to natural and artificial sounds according to individual characteristics. The survey consisted of two sessions conducted after collecting individual characteristics from participants. Session 1 evaluated preference for sound sources and emotional responses to sound presented from headphone and woofer by using the self-assessment manikin (SAM). Session 2 utilized to assess indoor soundscape. The results showed that both valence and arousal were highly correlated with sound preference, with higher valence and lower arousal tending to be more preferred. In the case of indoor soundscape assessment, water sounds showed significant differences between PC1 and PC2 on the comfortable-annoying axis and the intrusive-uncontrolled axis.

Effect of Added Natural and Artificial Sounds on Emotional Response and Indoor Soundscape to Residential Noises

This study investigated the effect of added natural and artificial sounds on emotional responses due to residential noises. The laboratory experiment conducted on three residential noise sources (child jumping and plumbing from upper unit and air conditioner outdoor unit) with different sound spectrum and temporal characteristics. In addition, combined sounds with residential, natural (one birdsong and three water sounds of waterfall, sea wave, and stream) and artificial sound (brown and white noise) were set. The experiment consisted of two sessions; self-assessment manikin and indoor soundscape assessment for each sound sources (single and combined residential noises) presented by headphone and woofer. As a result, most combined natural and artificial sounds resulted in more positive changes (higher valence and lower arousal score) than single residential noise. Among combined sounds, multiple natural sound (birdsong + stream) with residential noise showed significant difference from single residential noises such as air conditioner outdoor unit and plumbing noise. Meanwhile, eight affective attribute scale for indoor soundscape assessment showed two main perceptual dimensions and most added natural and artificial sounds had a role in increasing comfort.

Improving the quality of the acoustic environment in neonatal intensive care units: a review of scientific literature and technological solutions

There is an increased awareness of how the quality of the acoustic environment impacts the lives of human beings. Several studies have shown that sound pollution has adverse effects on many populations, from infants to adults, in different environments and workplaces. Hospitals are susceptible environments that require special attention since sound can aggravate patients' health issues and negatively impact the performance of healthcare professionals. This paper focuses on Neonatal Intensive Care Units (NICU) as an especially sensitive case representing a hostile acoustic environment in which healthcare professionals have little awareness of how unwanted sounds impact the perceived quality of the soundscape. We performed a semi-systematic review of scientific literature on sound assessment studies in NICU from 2001. A thematic analysis was performed to identify emerging themes that informed the analysis of 27 technological solutions for the assessment of sound quality in indoor and outdoor environments. Solutions were categorized by functions and evaluation methods and grouped according to the characteristics of the design components, i.e., acquisition, computation, and communication strategies. Results highlight a lack of solutions to assess the qualitative characteristics of indoor environments such as NICU and forecast the footprint that different sound sources have on the indoor soundscape. Such solutions are urgently needed to empower healthcare professionals, and especially nurses, to actively modify and prevent the negative impact of unwanted sounds on NICU and critical care soundscape.

Improving indoor soundscapes in primary school classrooms

A primary school soundscape is analyzed on a scale of pleasantness and arousal to determine the suitable sound environment for students.

Indoor soundscape in primary school classroomsa).

Soundscape research on indoor environments is emerging as a topic to be addressed for the design of supportive, healthier, and more comfortable spaces. Only a few studies so far addressed the context of educational buildings, mainly focusing on high schools and universities. This pilot study uses questionnaires based on pictorial scales to investigate the indoor soundscape of classrooms for primary school children (n = 130; 8-10 years old). Perceived loudness and the affective dimensions of pleasantness and arousal were explored. Besides the actual soundscape, the children's ideal soundscape was investigated as well. The results of the study indicate that the most frequent sounds in classrooms are generated by the students themselves (voices, movements) followed by the traffic. The urban context of the school modulates the children's perception when windows are open to ensure natural ventilation. Pleasantness is associated with students' age, perceived loudness, and frequency of children's voices in nearby classrooms. The frequency of hearing indoor sounds (children's voices) and sirens affects students' arousal. Our results indicate that children at school are mostly exposed to unpleasant sounds, whereas their preferred ones are music and nature-related ones. The findings have implications for the design of positive and inclusive learning environments.

Measuring, representing and analysing indoor soundscapes: A data collection campaign in residential buildings with natural and mechanical ventilation in England

A model for the assessment of perceived affective quality of indoor residential soundscapes is first applied in a field survey carried out in 61 dwellings in England. Objectives are i) to investigate measurement and indoor soundscape data representation, ii) to characterize soundscape appropriateness for home working and relaxation, iii) to test differences based on the ventilation strategy, and iv) to identify factors predicting indoor soundscapes. In dwellings with natural ventilation (N = 34) the survey was carried out with windows open, while in those with mechanical ventilation (N = 27) with windows closed and the system in operation. Parallel to the administration of the questionnaire, monaural and binaural measurements of the acoustic environments were performed. The study provides examples of data representation in the circumplex space defined by comfort and content dimensions. Soundscapes which are appropriate for work and relaxation are characterized by high comfort and low content, i.e., perceived as private and under control. Indoor soundscapes are strongly related to the perception of traffic noise, window opening, and sound pressure level, especially in the energy content of interference in speech perception through the Speech Interference Level parameter (SIL), factors that lead to reduced comfort and increased saturation of the environment. Moreover, aspects related to psychoacoustics (sharpness), contextual and building-related factors (ownership status and floor level) and cross-modal effects from other sensory modalities (perceived air quality and air temperature) have an impact. A threshold value of 32.7 dB for SIL was identified at which a neutral comfort is attained.

Day-to-day loudness assessments of indoor soundscapes: Exploring the impact of loudness indicators, person, and situation.

This study investigates loudness perception in real-world contexts using predictors related to the sound, situation, or person. In the study, 105 participants recorded 6594 sound environments in their homes, which were then evaluated based on the Experience Sampling Method. Hierarchical linear regressions using a loudness level based on ISO 532-1 allowed for obtaining the best model fits for predicting perceived loudness and explaining the highest variance. LAeq and LAF5 provided comparable results and may require less computational effort. However, the analysis shows that only one-third of the variance explained by fixed effects was attributable to the loudness level. Sixteen percent stemmed from perceived properties of the soundscape; 1% were attributable to relatively temporally stable, person-related predictors like participants' age; non-auditory situational predictors made no additional contribution. The results thus did not confirm previous findings on loudness perception under laboratory conditions, emphasizing the importance of the situational context. Along with the current paper, a comprehensive dataset, including the assessed person-related, situational, and sound-related measures as well as LAeq time-series and third-octave spectrograms, is provided to enable further research on sound perception, indoor soundscapes, and emotion.

Indoor soundscape model: Assessing contextual factors in open-plan offices on university campuses in Surabaya, Indonesia

Evaluation research in Western countries shows that soundscape perception and work behaviour in an open-plan office are negative due to uncontrolled sound levels and diminished visual and acoustic privacy. This condition resulted in a noteworthy diminution in employee performance and comfort. Most offices in large cities, including those in Indonesia, also follow the trend of adopting an open-plan system. For this reason, it is necessary to conduct further studies in the local environment. Contextual experience is a key aspect in indoor soundscape studies, of which subjective evaluation is an important part. This study further investigates the causal relationship between contextual factors related to space usage and personal and demographic aspects on psychological, expectation, soundscape perception, and work behaviour aspects. The questionnaire survey was conducted on full-time employees at six administrative offices on two university campuses in Surabaya. Partial least squares structural equation modelling (PLS-SEM) was used to analyse statistically the collected data and to test the formulated hypotheses. The results reveal a significant path from personal and demographical to psychological, which has the highest estimated t value of 9.438 and is supported by a significance level of p < .01 (t0.01>2.58). Social-cultural characteristic indicators, namely, societal values and lifestyle, have the highest loading and consequently have a large influence on soundscape perception and work behaviour in the local environment. This results in certain work behaviour reflected in the reactions, responses, soundscape preferences, and activities of employees working in the local environment, which differs from that of those residing in Western countries.

The interactive effects of traffic sound and window views on indoor soundscape perceptions in the residential area.

Environmental noise has long been considered one of the unwelcome aspects of urban life at home. An increasing number of scholars have studied improving indoor acoustic comfort by using the soundscape approach. However, much uncertainty still exists about the relationship between the audio-visual environment and indoor soundscape perception. The current study investigates the interaction effects of traffic sound and window views on indoor soundscape perceptions in residential contexts. Thirty-two participants were presented with 51 scenarios (a combination of 17 window views and three aural stimuli) and requested to assess their soundscape perceptions in a VR experiment. Results showed that traffic noise could moderate the impact of nature, road, and building views on pleasantness, while it can also moderate the effect of water sound and road view on eventfulness. In particular, natural window views were found not to lead to a more pleasant indoor soundscape necessarily; natural window views even decrease the pleasantness of indoor soundscape in the case of heavy traffic noise outside the window. Besides, overall visual indicators, including complexity and openness, have an interactive effect with traffic sound on pleasantness. Last, pleasantness is found to be associated with the appropriateness of indoor soundscape.

Sound environment of bedrooms in typical long-term care facilities in China

Evidence shows that older individuals would be more sensitive to noise, whereas sound environment of healthcare facilities for seniors in China is largely ignored. In this study, acoustic measurements were carried out over 24 hours in twelve bedrooms in five typical long-term care facilities, including two nursing homes and three adult homes in Kunming, China. Sound perception and preference of elder and nursing staff were also investigated through questionnaire surveys. The results showed that the noise levels of the measured bedrooms reached 47.4~59.3 dBA during the daytime and 39.1~49.3 dBA during the nighttime. The nursing homes were measured higher noise levels than the adult homes due to nursing care activities. Meanwhile, results showed a more significant gap between the bedrooms facing the streets and those not facing the streets. In terms of subjective evaluation, 'traffic noise' was the most common and unwanted noise source considered by both recipients and staff. Recipients from nursing homes indicated that noise has more significant impact on their 'sleep,' 'health' and 'relaxation' than those from adult homes. The indoor soundscape could be improved by introducing some natural sounds such as 'stream,' 'birds,' 'wind' and 'rain' which were considered as the wanted sounds by most participants.

Principle dimensions of perceptual attributes in indoor public spaces

This study aims to analyze the principal dimensions of perceptual attributes in indoor public spaces. Healthcare, working, cultural, educational, leisure, worship, and transportation spaces (e.g., bus, train, metro stations, and airports) were chosen as public spaces. Three members of the research team independently listened to all 70 binaural recordings, taken from indoor spaces, and for each recording identified whether human-generated sounds (e.g., conversation, laughter, footsteps, and coughing), technology-related sounds (e.g., mechanical and electronic sounds) and/or environmental sounds dominated. University students (n=120) performed a listening test to assess 70 binaural recordings of indoor soundscapes on users' attribute scale. Principal component analysis shows that there are two prominent groups: pleasantness and eventfulness. Perceived sound environments dominated by technology-related sounds were found to be unpleasant, while the acoustic environments dominated by human-generated sounds were eventful.