Non-acoustic Factors Research Articles

Development of a conceptual framework for a new international standard on non-acoustic factors

The human response to a sound environment is influenced by factors that interlink the person, activity, and place. These factors are often referenced as discrete elements of the "context" in soundscapes, and as "non-acoustic factors" within the noise and health community. Despite their importance, researchers and practitioners tend to use different terminology and methods for investigating them, which complicates evidence synthesis and recommendations for designing healthier sound environments. Since 2022, Working Group 68 within ISO TC 43/SC 1 has been developing a new Technical Specification to standardise the definition and use of such non acoustic factors. Part 1, due for publication in 2025, will include a definition and a conceptual framework. As part of this work, we conducted a rapid scoping literature search to assist in the development of the conceptual framework. Fourteen articles were shortlisted, which were used to draft a framework that reflects the definition of non-acoustic factors, including its main categories (personal, psychosocial, tangible/environmental, and situational) and the moderating and mediating role of non-acoustic factors on the human perceptual and affective response (emotional and behavioural) and associated health outcomes.

The importance of considering both acoustic and non-acoustic factors in mitigating the effects of aircraft noise on residents' well-being

This study examines the effect of temporal changes in aircraft noise exposure in Vietnam, focusing on the influence of non-acoustic factors. Using data from surveys conducted around Tan Son Nhat Airport (TSN) and Noi Bai Airport (NB), the study explores changes in noise exposure levels, evaluates the applicability of existing regulations, and assesses the impact of non-acoustic factors. Surveys conducted around NB between 2014 and 2018 examined operational changes, while those around TSN investigated the impact of the COVID-19 pandemic between 2019 and 2023. Findings suggest that non-acoustic factors significantly shape community responses to noise. This study underscores the importance of implementing comprehensive noise regulation policies that consider both acoustic and non-acoustic factors in mitigating aircraft noise impacts on residents' well-being, particularly in emerging and developing countries.

Health effects related to wind turbine sound - a rapid evidence review covering 2020 - 2024

Wind energy plays an important role in the delivery of net zero and energy security commitments, and globally wind additions are forecast to more than double by 2028 compared with 2022. Permitting frameworks have been identified as a key barrier to growth of onshore wind, and the health effects of wind turbine sound emissions remain a primary concern to local communities. Evidence reviews published in 2017 and 2020-21 concluded that the health effects literature is increasing, but there are still gaps, especially for health endpoints other than annoyance, and how non-acoustic factors can moderate and/or mediate self-reported health outcomes. We carried out a rapid evidence review covering the period July 2020 to February 2024 to determine if newer evidence is addressing these gaps. Of the 22 studies about health effects, most focused on self reported health, annoyance, and sleep disturbance. Studies about other health effects remains limited. Studies on "social acceptance" (n=10) continue to show the importance of non-acoustic factors,such as attitudes and personal characteristics are in impacting outcomes. No intervention studies were identified. Due to variations in study design, exposure and outcome measures, and how non-acoustic factors are characterised, it remains challenging to make generalised recommendations to mitigate health impacts.

Directional perception and its influence on noise annoyance from unmanned aerial vehicles

The use of Unmanned Aerial Vehicles, commonly known as drones, has seen a rapid increase in recent years and is projected to continue growing. As a result, drones have become a new source of environmental noise pollution, and the potential for annoyance reactions among the population is likely to increase. The literature shows that the noise from drones is more annoying than noise from road traffic or aircraft due to its unique acoustic characteristics, such as pure tones and high-frequency broadband noise. However, it is possible that non-acoustic factors, such as the listener's inability to locate the source, play a role in the perceived annoyance. This study aims to test and conclude whether this is a contributing factor to why drone noise is perceived as more annoying than other environmental noise sources.

The effect of aircraft noise on noise annoyance in DEBATS and NORAH pooled analysis: Role of non-acoustic factors

We investigated the dose-response relationship between aircraft noise levels and noise annoyance in the French DEBATS study including 1244 participants in 2013 and a sub-study of the German NORAH study including 1039 participants in 2014. In both studies, annoyance due to aircraft noise was assessed using the ICBEN 5-points question. High annoyance was defined according to ISO/TS-15666 (HAV). Outdoor aircraft noise levels were modelled for the participants' home addresses. The moderation roles of noise sensitivity, gender and age were investigated. About 18% of the participants in the DEBATS study reported to be highly annoyed vs 54% in the NORAH study. The mean noise levels (Lden) were similar (54 dBA in DEBATS and 52 dBA in NORAH). In the pooled analysis, high noise annoyance was associated not only with aircraft noise levels, but also with non-acoustical factors such as noise sensitivity, age and trust in authorities. Noise sensitivity moderates the effect of aircraft noise levels on aircraft noise annoyance (p-value of interaction = 0.02), while age and gender do not.

Qualifying and quantifying the different ways in which people are annoyed by aircraft noise

Aircraft noise remains a major problem for many people living near airports, despite the efforts of the various air traffic operators and aircraft manufacturers to reduce the nuisance. Noise abatement usually relies on quantitative approaches based on noise measurements at source or in residential areas. However, field studies have shown that the level of annoyance experienced within a given noise exposure zone varies widely, demonstrating that noise levels alone do not explain the experience of local residents. The present work brought together a wide range of disciplines (aeronautics, acoustics, linguistics, psychoacoustics, social and environmental psychology) to define a common framework for reconciling field and laboratory studies on aircraft noise annoyance. A survey of 1250 people living near airports enabled us to precisely qualify the annoyance experienced, and to identify 6 highly differentiated annoyance profiles based on non-acoustic factors. Focus groups and laboratory experiments with people living near airports revealed an impact of annoyance profiles on both qualitative and quantitative evaluation of noise annoyance, which confirms the diversity of their experiences in the same listening situation.

The city at ear level - Qualifying the role of soft data in soundscape development and research

The ISO/TS 12913-series on Soundscape, has the potential to exert significant influence on urban life, impacting infrastructural development, sustainability practices, and overall quality of life. This paper underscores the imperative of exploring the city's soundscape at ear-level, emphasizing a perspective of sonic citizenship wherein the individual's lived experience takes precedence. Such a perspective focuses on an understanding of soundscapes as dynamic attuning relations, including how multisensory atmospheres shaped by non-acoustic factors influence our assessment of soundscapes. Citizens engage in negotiating, performing, and sharing responsibility for these soundscapes. We propose how urban interventions and experiments can help glean finer insights into people's lived experiences and capture such nuanced, often subconscious aspects when developing urban soundscapes. These initiatives aim to motivate and empower a diverse spectrum of citizens, to engage in co-creating the urban development process. We argue that fostering such participatory activities enhances awareness and underscores the urgency of high-quality soundscapes in collaboration with relevant authorities and urban stakeholders. Additionally, these interventions yield soft data elucidating cultural and social practices, enriching our understanding of the experiential dimensions of soundscapes and informing future urban development.

Predicting the impact of integrated audio-visual environments on perceived restorative benefits across different park types: A field study based on seven parks in Hangzhou, China

The human perception of environments is a complex mechanism, influenced not only by visual and auditory stimuli and their perceptual outcomes, but also by personal characteristics, site types, and other factors that affect people's restorative experiences. However, there is little research that treats it as a complete systemic phenomenon to reveal its integrated impact. We surveyed 1161 visitors in seven urban parks in Hangzhou, China, and collected information on audio-visual stimuli. Using structural equation modeling and multi-group analysis, we initially examined the comprehensive impact of acoustic factors, non-acoustic factors, and individual characteristic variables on perceived restorativeness. Subsequently, we studied the effects of different park types on the constructed multivariate comprehensive model. The results confirm that the presence of different types of sound sources within landscape features can impact the auditory affective quality dimension, which in turn affects visitors' perceived restorative experiences. In addition, the reported mediating pathways revealed that visual elements related to nature, by providing high-quality visual landscapes, enhance the pleasantness of soundscapes and yield greater restorative benefits in park environments. A new finding of the study was that, although the eventfulness of the soundscape negatively affects perceived restorativeness, the presence of high-quality visual landscapes in the environment can compensate for this deficiency. Further multi-group analysis results show that landscape features and visual perceptual quality indirectly influence perceived restorativeness through the auditory affective quality dimension, resulting in varied correlations across two types of park. Moreover, the pleasantness of soundscapes consistently has a significant effect on perceived restorativeness in both types of parks; however, in parks oriented towards activity, the eventfulness dimension of soundscapes does not significantly affect perceived restorativeness. Lastly, the influence of landscape features on perceived restorativeness, mediated by types of sound sources, is both direct and indirect, leading to diverse correlations across different park environments. These detailed findings and guidelines for audio-visual interaction design will aid in the planning and development of urban soundscapes.

Towards developing a model of adaptive acoustic comfort in the built environment: A thematic analysis from an expert focus group

The adaptive capacities of building occupants have so far been primarily investigated in relation to the thermal climate through the adaptive thermal comfort model. However, the concept of adaptation extends beyond thermal conditions and is relevant to other sensory modalities, such as acoustics. This is significant for both human health and well-being, as well as environmental considerations. The latter aspect is linked to potential variations in acoustic sensitivities between naturally ventilated and mechanically ventilated buildings, which, if identified and acknowledged, could lead to a greater applicability of passive ventilation strategies through tailored acoustic criteria. Drawing from thematic analysis of discussions held in a focus group comprising 8 experts in acoustics, soundscape, and adaptive thermal comfort, this study aims to 1) delineate the underlying assumptions of acoustic adaptation in built environments, and 2) establish a research agenda towards developing a framework for adaptive acoustic comfort. The identified themes include: the definition of adaptive acoustic comfort, potentially contributing acoustic and non-acoustic factors, differences and similarities with the adaptive thermal comfort model, and the methodology for collecting data. In terms of results, 1) adaptive acoustic comfort would be based on potential modifying effects of recent past acoustic exposure and other environmental factors (including multi-domain effects), contextual, and personal factors on people's acoustic expectations and preferences. 2) To test this concept, the very first step will have to be the construction of a comprehensive global acoustic comfort database.

Summary of National Standards on classroom acoustics: The data collection

Improving acoustic comfort in classrooms is paramount for enhancing intelligibility, fostering student concentration, and alleviating the vocal strain on teachers. The global discourse on acoustic quality in educational buildings has intensified in recent decades, with each country establishing its unique set of building codes, standards, guidelines, and voluntary point protocols to delineate acoustic quality parameters. Geometrical and architectural classroom variations, influenced by cultural and historical contexts, further contribute to the diversity of approaches. The present work provides a summary that investigates and compares local standards across various countries worldwide, aiming to offer a holistic understanding of the classroom acoustic landscape. The motivation for this summary lies in finding regulations that are not easily searchable on Scholar or Scopus. It involves human interpretation and consideration of building codes, often in local languages. More than 70 experts, distributed across continents, were queried about his local standards, their enforceability, room criteria, design rules; and non-acoustic factors like classroom geometry, average occupancy, and flexibility of learning spaces. By synthesizing insights from diverse regions, this study aspires to provide a global perspective on the state of acoustic quality in educational settings, shedding light on potential areas for improvement.

Methods for managing soundscape quality: Evidence from Denali National Park and Preserve

The purpose of the United States national park system is to preserve resources unimpaired for the enjoyment of future generations. At Denali National Park (DENA), high levels of air tour traffic and air transportation present challenges to preserving wilderness character. Accordingly, the park attached high priority to measuring visitor impressions of soundscape quality. Visitors in four distinct settings rated the acceptability of five randomly chosen recordings of aircraft noise. We used a cumulative link mixed model to fit visitor’s response to acoustic and nonacoustic factors. The negative effects of increased noise were moderated for visitors who were interested in taking an air tour. To be conservative, we examined visitors uninterested in an air tour and found the probability of rating aircraft noise as unacceptable at 54 dB LAeq, 30 s or higher was 26%. For context, noise above 55dB is incompatible with outdoor, rural activities. Visitor response predictions were joined to a spatial model of aircraft noise propagation to create a map depicting the acceptability of aircraft noise in DENA’s frontcountry area. The map can be used to forecast the range of soundscape conditions park visitors are exposed to, inform hiking recommendations for visitors, and evaluate park management zones.

The contributions of acoustic and non-acoustic factors to spatial release from masking

The ability to identify speech at worse signal-to-noise ratios when the maskers are spatially separated compared to when they are colocated is called spatial release from masking (SRM) and is thought to be a combination of monaural and binaural advantages arising from spatially separating the target from the maskers. Also, a host of other cognitive skills including attention, working memory, and executive function that support listeners’ ability to segregate, track and attend to a “target” signal while tuning out other unwanted signals contributes to understanding speech better in complex environments. Previous research with young normal hearing listeners from our lab indicated that SRM was predicted by an individual’s ability to use binaural cues (ITD thresholds), switch attention between two streams of information (trail making test) and ability to suppress irrelevant information (flanker task). Here, we present data from older listeners with varying hearing abilities on acoustic (envITD sensitivity) and non-acoustic tasks measuring attention (auditory and visual single and dual task), processing (trail making task), executive control (flanker task) and speech in noise tests (spatial release from masking using coordinate Response Measure sentences). The relationship between these acoustic and non-acoustic factors to speech understanding in complex listening environments will be discussed.

Development and Validation of the Aircraft Noise related Fairness Inventory (fAIR-In)

Annoyance caused by aircraft noise is largely influenced by non-acoustic factors, such as the attitude towards the noise source, perceived control over the noise and the predictability of noise occurrence. Underlying many of these non-acoustic factors is perceived fairness, e.g., regarding information provision by the noise source or opportunities for noise-affected residents to participate in noise-related decision-making. A validated instrument to assess a variety of fairness aspects in surveys has been lacking. Therefore, the Aircraft Noise related Fairness Inventory (fAIR-In) has been developed, a multifaceted psychometric instrument. With 32 items, the fAIR-In assesses aspects of distributive, procedural, informational and interpersonal fairness of airport management. The development of the fAIR-In as well its validation by means of data from 1,367 residents living around three German airports are presented. Results reveal a high degree of predictive validity with regards to annoyance, airport and air travel acceptance, as well as protest behavior. Our findings indicate that the fAIR-In is a useful tool for capturing existing community perceptions of the airport, as well as facilitating the design, monitoring and evaluation process of interventions aimed at improving the relationship between the airport and its residents.

Evaluation of risk perception related with environmental noise among residents living in different vicinities of wind turbines

ABSTRACT This cross-sectional study assessed residents' risk perceptions and associated factors in three rural areas by administering a face-to-face questionnaire to 282 subjects. The association between the perception of risk related to wind turbines and related factors such as noise and annoyance was analysed. Outdoor A-weighted sound pressure levels were measured for all. According to regression analysis, age (B: -0.008, 95% CI: -0.015/-0.002), education (B: 0.415, 95% CI: 0.148/-0.682), noise level day (B: -0.040, 95% CI: -0.068/-0. 013), noise annoyance indoors (B: 0.504, 95% CI: 0.227/0.781) and distance (B: 0.000, 95% CI: 0.000/0.000) had a significant effect on high risk perception (p < 0.05). This demonstrates that, in addition to noise, non-acoustic factors also influence risk perception. Ensuring community participation and considering distance before installation could prevent negative risk perceptions and annoyance.

Soundscape and subjective factors affecting residents' evaluation of aircraft noise in the communities under flight routes.

Aircraft noise is one of the most significant sources of environmental pollution in large cities. During the COVID-19 pandemic, strict lockdown in community might increase residents' discomfort with the noise, which could disrupt public activities and reduce subjective well-being. Most of the existing studies considered aircraft noise as a single sound source, which have ignored the influence of other sounds in the community. This paper applied field survey to identify the soundscape and non-acoustic factors related to aircraft noise evaluation. Paper questionnaires were delivered to select residents of three sample residential areas near Shenzhen Bao'an International Airport to investigate residents' general health, evaluation of aircraft noise, community activities, and attitudinal factors. The relationship between respondent's noise evaluations and subjective factors were investigated through statistical analyses controlling for measured aircraft noise levels and the existence of soundscape facilities. The results indicated that the negative effects of aircraft noise were enhanced during the lock down, especially for frequent space users and those residents in poor health status. Under conditions of similar levels of aircraft noise exposure, communities with more birdsong and fountain sounds had lower proportion of highly annoyed respondents and higher level of soundscape ratings. This paper further indicated that personal factors including fear of air travel, noise sensitivity, and the frequency of outdoor activity had increased the level of annoyance to aircraft noise, while higher degree of annoyance to aircraft noise was associated with poor health status. The findings implied the moderating effects of subjective factors and the restorative effects of natural sounds, which could inform aircraft noise control and community consultation strategies by protecting vulnerable populations and creating community soundscape facilities. Future research might conduct a pre- and post-experiment to estimate the potential causal impact of the soundscape intervention.

EEG alpha wave responses to sounds from neighbours in high-rise wood residential buildings

This study explored electroencephalogram (EEG) alpha waves (α-EEG) in response to neighbours’ sounds in wood residential buildings. Experiments were carried out in a laboratory to collect α-EEG data in distinct acoustics scenarios. A series of impact and airborne sounds were generated using loudspeakers and subwoofers, while the participants sat comfortably in a simulated living room wearing EEG headsets. Impact sounds were those of footsteps of adults walking on floors equipped with different timber floor configurations, whereas airborne sounds were of speech and music digitally filtered to resemble the good and poor sound insulation performances of lightweight vertical partitions. The sound sources were presented both individually and in combination (e.g. footsteps combined with music or speech). Noise sensitivity and attitudes towards neighbours were introduced as non-acoustic factors. The study highlighted significantly higher α-EEG in response to footsteps heard through floors characterised by low impact sound pressure levels (SPL) and to music heard through partition walls with low sound reduction indices. The effective duration of the autocorrelation function, τe, was computed to investigate subjective preference, and significant differences between sounds heard at various SPLs were identified for speech and music. Footsteps sounds in combination with an airborne source elicited higher α-EEG when compared to single footsteps sounds. Participants with self-reported low noise-sensitivity and positive attitude towards neighbours showed significantly larger α-EEG responses when exposed to sounds from neighbours than those who had high noise-sensitivity and negative attitude towards neighbours.

Being a Fair Neighbor-Towards a Psychometric Inventory to Assess Fairness-Related Perceptions of Airports by Residents-Development and Validation of the Aircraft Noise-Related Fairness Inventory (fAIR-In).

Aircraft noise causes a variety of negative health consequences, and annoyance is a central factor mediating stress-related health risks. Non-acoustic factors play an important role in the experience of annoyance where the aspect of fairness is assumed to be a vital component. This paper describes the development of the Aircraft Noise-related Fairness Inventory (fAIR-In) and examines its factorial validity, construct validity and predictive validity. The development of the questionnaire included expert consultations, statements from airport residents and a large-scale online survey around three German airports (N = 1367). Its items cover distributive, procedural, informational and interpersonal fairness. Via mailshot, almost 100,000 flyers were sent out in more (>55 dB(A) Lden)- and less (≤55 dB(A) Lden)-aircraft-noise-exposed areas around Cologne-Bonn, Dusseldorf and Dortmund Airport. Thirty-two items were carefully selected considering reliability, theoretical importance and factor loading calculated via exploratory factor analysis (EFA), with all facets achieving high internal consistency (α = 0.89 to 0.92). The factorial validity, analyzed via a confirmatory factor analysis (CFA), revealed that viewing distributive, procedural, informational and interpersonal fairness as distinct factors produced a better fit to the data than other categorizations with fewer factors. The fAIR-In shows adequate results in terms of construct validity and excellent results in terms of the predictive validity of annoyance by aircraft noise (r = -0.53 to r = -0.68), acceptance of airports and air traffic (r = 0.46 to r = 0.59) and willingness to protest (r = -0.28 to r = -0.46). The fAIR-In provides airport managers with a reliable, valid and easy-to-use tool to design, monitor and evaluate efforts to improve the neighborliness between an airport and its residents.

How much noise is too much? Methods for identifying thresholds for soundscape quality and ecosystem services

The United States National Park Service mandate is to conserve park resources and provide superlative visitor experience. In the context of acoustic resources, Denali National Park and Preserve provides an advantageous opportunity to understand the effect of aircraft noise on visitor experience because it possesses high levels of air tour traffic in a park renowned for its remote, wilderness character. Park visitors in four different settings were asked to rate the acceptability of recordings of aircraft noise, presented in randomized order relative to noise level. A cumulative link mixed model fitted visitor assessments to acoustic and nonacoustic factors. In addition to noise level, interest in an air tour was an important predictor of sound clip acceptability. For visitors uninterested in an air tour, the probability of rating aircraft noise as unacceptable at 54 dB LAeq,30 s or higher was 26%. For reference, this aligns with federal guidance that identified 55 dB as a threshold for interference with outdoor activities at rural residences and schools. Predictions of visitor response were joined to a spatial model of aircraft noise propagation to map visitor acceptability of aircraft noise in Denali’s entrance area (frontcountry). This map can be used to assess the condition of park management zones, to inform hiking recommendations for visitors, and to predict the range of soundscape conditions experienced by park visitors.

Effect of neighbours sounds in wooden residential buildings on restorative EEG rhythm (Alpha waves)

The present study aimed to explore the effect of neighbours sounds commonly heard in wooden residential buildings on restorative EEG rhythm represented by Alpha waves. Thirty participants took part in a listening test which was performed to collect EEG data in distinct acoustics scenarios. Noise sensitivity and attitude toward neighbours were introduced as non-acoustic moderators and assessed through questionnaires before the experiment. A series of impact and airborne sounds were presented through loudspeakers and subwoofer, while participants sat comfortably in the simulated living room wearing the EEG headset (B-alert X24(r) system). The impact sound sources were two types of footsteps, adult walking and child running, recorded in a laboratory on different floor configurations and thus, varying in sound pressure level and frequency characteristics. The airborne sound sources were a lively conversation and a piece of classical piano music, digitally filtered to represent good and poor sound insulation performances of vertical partitions. The effect of sound stimuli and non-acoustic factors on restorative EEG rhythm corresponding to Alpha waves (8-13 Hz) was then analysed. Differences in response to distinct acoustic scenario were observed. Additionally, Alpha band activity showed to be affected by noise sensitivity and attitude toward neighbours of participants.

Why listening matters

Sound is the only one of our senses that remains active while we sleep. Through hearing we test our safety at distance and in the dark. It can also condition the way we feel. Noise can affect our health and well-being negatively but sound may do so positively. Acousticians are used to measuring noise but the more positive effects of sound less well understood. The idea that sound can reduce stress and inhance our sense of wellbeing and even improve our health is a tantalising target for soundscape designs in the future but we need more fully to understand how to achieve it in a scientific way. We know that a tranquil place does not need to be quiet for instance, and that context and non-acoustic factors are important in the perception of tranquillity. We know that natural sounds: waves breaking, rain, leaves rustling, water babbling, birdsong; and some anthropogenic sounds: a familiar voice, the murmur of conversation, music; can contribute to a positive soundscape. Some examples and the current understanding of why this is, taking in cues from neuroscience, medicine and psychoacoustics are explored leading to quantification of these benefits for application in soundscape analysis and, ultimately, design.