Summary

The idea behind the research programme ”Soundscape Support to Health” is to exploit variations in the acoustic soundscapes in order to create a significantly improved environment for the population even though the sound levels at the busy streets and roads will remain rather high. Much emphasis is put on the extra protection and development of quiet places and sides of buildings and to determine the health benefits of this in the population.

A conceptual differentiation is made between the acoustic soundscapes and the perceived soundscapes. Whereas the acoustic soundscapes are assessed by physical measuring instruments (acoustic properties), the perceived soundscapes are assessed by perceptual scaling methods utilizing persons (perceptual features). For several of the adverse effects of community noise, the perception of the sound environment works as an intervening variable between the acoustic impact and the health impact.

For assessing dose-response relationships between soundscapes and effects on health and well-being, a number of study sites with different sound levels from road traffic were chosen. Study sites type A are examples of building areas where some residents have access to at least one quiet side of their dwellings and other residents do not have access to any quiet side of their dwellings.

The quiet side should comply with the following definition:

Study sites type B are examples of building areas where the sound level of noise from traffic is reduced through erection of new buildings which will partly shelter one side of the residential buildings from direct noise exposure from road traffic. One such area was selected – in a central district in the city of Örebro.

Assessment of health effects
The overall scientific approach in this programme recognises that personal and social factors intervene between noise immission and annoyance (and various types of interference with activities) which may induce adverse effects on sleep and adverse effects on health and well-being in terms of stress-related psychological and physical symptoms. Noise at high sound levels also causes direct effects, e.g. masking of speech, awakenings and vegetative effects.

Three projects within the programme have been carried out to assess health effects of soundscapes:

(a) Cross-sectional studies, related to study sites type A

(b) Longitudinal studies, related to study site type B

(c) Experimental / quasi-experimental studies on sleep

The goal of the cross-sectional studies was to obtain knowledge on the relationship between individual noise exposures, including having access to a quiet side of the dwelling, and various adverse health effects, behaviour and self-estimated noise sensitivity. In total, data from 956 individuals has been collected in the cross-sectional studies.

The effects on human’s health and well-being were assessed by questionnaires. Individual data on various health effects were linked to data on individual acoustic soundscapes. Data from a sub sample of 106 residents was also linked to data on individual perceived soundscapes. Adverse effects on health and well-being were analysed in relation to acoustic and perceived soundscapes.

The effectiveness of shielding buildings in reducing adverse health effects was determined in the longitudinal study before and after shielding-building intervention in order to validate noise-induced health effects assessed in the empirical cross-sectional studies. The effects on health and well-being were assessed with questionnaires similar to those used in the cross-sectional studies. In addition, an in-depth study on sleep was carried out in a sub sample of residents by means of questionnaires on sleep and by means of wrist-actimetry.

Eighty residents took part in the before study. Of these 45 residents also took part in the after study. The sub sample in the sleep study was 24 and 10, respectively, before and after the shielding building was built.

Two series of experimental / quasi-experimental studies were carried out in a sleep laboratory and in the home environment. The purpose was to gain additional knowledge on the relation between acoustic soundscapes and adverse effects on sleep. The main goal was to assess the effects on sleep of noise from ventilation equipment, as compared with traffic noise alone and traffic noise in combination with ventilation noise. It was also investigated if there are differences in results for sleep studies performed in laboratory and in field settings.

Perceived soundscape research
The overall strategy in the soundscape research recognises that good environmental quality embraces good soundscapes. Soundscapes are composed of a variety of sounds, road traffic noise inclusive. Little is, however, known on what kinds of sound compositions and what criteria should be set for good-quality soundscapes in urban residential areas. The main goal of the perceived soundscape research was therefore:

(a) To deliver methods for measuring various features of perceived soundscapes and to use these for assessing perceived soundscapes in study sites type A and type B;

(b) To determine residents’ psychoacoustical relationships for soundscapes, including the role of personal factors such as noise sensitivity, in study sites type A;

(c) To evaluate the efficiency of abatement actions in improving the perceived soundscape (e.g., shielding buildings or sound insulation) in study sites type B.

Innovative methods for assessing perceived soundscapes were developed. They constitute the tools necessary for studying perceived soundscapes at the study sites. Data on perceived and acoustic soundscapes were collected in connection with the cross-sectional and longitudinal health studies utilizing sub-samples of participating residents classified as noise sensitives and noise non-sensitives. The psychoacoustical soundscape studies consisted of:

(a) Quasi-experimental studies consisting of structured listening walks with 149 residents and 894 places, outdoors and indoors, jointly with binaural and monaural recordings of two acoustical soundscapes at each place;

(b) Questionnaire studies on long-term detailed soundscape appraisals including sound source identification and source-specific annoyance;

(c) Experimental studies on residents’ perceived and acoustic soundscapes, including the effects of noise sensitivity.

The new developed methods of measurement included sound-source identification, master scaling of soundscape loudness, quality of soundscapes by perceptual-emotional attribute profiling, and perceived quality of soundscapes by multidimensional scaling of similarity.

In total 1788 30-s soundscapes were recorded during the listening walks. After quality control a soundscape database was created consisting of more than 1600 binaural acoustic and perceived soundscapes. In addition to conventional sound analyses, 125-ms evolutionary spectra (“waterfalls”) were computed in order to obtain detailed information on changes of spectra and levels with time. The selection of soundscapes to be analysed was motivated by the corresponding data set of perceptual-emotional attribute profiles collected from the residents. These profiles convey qualitative information on the perceived soundscapes whereas the “waterfalls” convey corresponding qualitative information on the acoustic soundscapes.

Prediction and measurement of acoustic soundscapes
The acoustic soundscapes are characterized by an extreme complexity due to a multitude of sources, fluctuation in time and space, meteorology, etc.

For the directly traffic noise exposed areas, conventional prediction methods are used. The situation is different for quiet/shielded areas. Prediction methods were needed, which take into account a multitude of sources, the influence of buildings both as barrier and as “scattering object”, meteorological parameters, if sources at longer distance are important, the geometric distribution of the traffic and the ground surface geometry. For this situation the existing prediction methods – such as those developed in the North 2000 project – fail even when extended to include multiple façade reflections. This is the reason why the courtyards in our study sites turned out to be less quiet than predicted from our initial calculations.

A so-called flat city model was developed. Although the method was shown to work reliable for shielded areas, it requires a substantial amount of measurements on the field site to get sufficient accuracy. Two different prediction schemes for prediction of soundscapes in quiet and shielded areas without the need for measurements in the field are developed. The first model focuses on the propagation of sound inside single so-called street canyons and on the interaction between adjacent canyons (e.g. street and backyard). Preliminary calculations using the model show reasonable agreement with measurements – if a sufficient number of roads are included – not only in A-weighted values, but also over frequency.

The second model focuses on the propagation of sound over a long range inside residential areas with their varying building structure. A statistical approach is used which is based on the treatment of noise as wave-packets that are reflected and scattered through the city landscape.

Measurements for determination of long time exposure were mainly made in positions at façades (in front of a window) exposed to a traffic flow typical for the test site. Also short time measurements were carried out, being less expensive and able to be carried out under controlled conditions over the whole measurement period. In parallel to the measurement of noise, traffic was counted on the road closest to the measurement position. The sound exposure for all dwellings included in the field study was calculated.

Our results show a strong relationship between annoyance and sound levels and that access to a quiet side of the dwelling reduces the annoyance by 10 - 20 % in our examples, depending on the sound level from road traffic at the most exposed side.

Health and well-being is supported, and annoyance is reduced, by a soundscape in the dwelling (incl. balcony and outdoor places) that provides opportunities for

- Rest and restoration during daytime

- Good sleep even with windows slightly open

- Relaxed conversation and listening to radio/TV

- Natural behaviour, e.g. opening windows and use places in- and outside the dwelling as planned

- Nearby green, restorative areas

Disturbances of rest and restoration are experienced by about 10 % of the population if there is access to a quiet side and the sound level at the most exposed side is around LAeq,24h 55 dB. For dwellings with access to a quiet side these disturbances increase with about 10 % as the sound levels increase with 5 dB (i.e. 30 % at 65 dB). For dwellings without access to a quiet side the increase in disturbances of rest and restoration is almost 15 % when the sound levels increase with 5 dB (i.e. 20 % at 55 dB and 45 % at 65 dB).

Our studies show that disturbances of activities involving speech communication indoors are not very frequent (less than 10 % disturbed) if windows are closed and the outdoor sound levels don’t exceed LAeq,24h 53-57 dB (correspond to ca. 23-27 dB indoors). The prevalence of disturbance of communication outdoors is ca. 10 % if sound levels don’t exceed LAeq,24h 46-50 dB.

A large majority of the population prefer to sleep with windows slightly open. If the sound levels from road traffic outside bedroom windows don’t exceed LAeq,22-06 40-44 dB 2 m from the façade, bedroom windows can be kept slightly open without causing extensive (approximately 10 % disturbed) sleep disturbances. Noise-induced sleep disturbances increase strongly with higher sound levels outside bedroom windows.

Our studies confirm the results obtained in previous longitudinal studies that traffic noise causes stress-related psychosocial symptoms. In areas with high sound levels (LAeq,24h 63-68 dB) without access to a quiet side the prevalence of daily or weekly symptoms: very tired, feeling stressed, unsociable and irritated were significantly more frequent than in the most quiet area (LAeq,24h ca 45 dB at both sides of the dwelling). The relationship between traffic noise and stress-related symptoms found in our study is strengthened by the results from international studies, which suggest a higher prevalence of heart disease in areas exposed to road traffic noise of 65-70 dB.

Based on our results it is possible to propose the following criteria for sound levels from road traffic not to be exceeded outdoors to ensure 90 % of the general population a healthy sound environment free from adverse effects of noise from road traffic:

Health effects, main results from the longitudinal study
The experience from the longitudinal study is that it is of utmost importance that expertise from the fields of acoustics, environmental psychology and medicine take part and influence the renewal of buildings at an early stage of planning. In the present intervention example this was not the case and the shielding building gave very little reduction in sound levels, in most cases only 1 dB.

Though the standardised annoyance questions (scale 1-5 and 0-10) did not display any change in annoyance before and after intervention, the comparative questions were more sensitive and revealed a significant change in how often the respondent noticed noise from traffic and a larger significant change in to what degree various activities were affected by road traffic noise.

Main results from the experimental/quasi-experimental studies on sleep
It was found that results obtained from laboratory experiments do not exaggerate the effects of road traffic noise on sleep and if sleep is assessed with the same methods and if a homelike environment is created in the laboratory these results are reliable and allow for comparisons and generalisations to be made to the home environment.

Effects on sleep obtained by questionnaires and by actigraphy were contradictory and the results obtained by questionnaires seem more reliable.

Road traffic noise of LAeq,22-06 39 dB and LAmax 55 dB causes a reduction in sleep quality with about 20 % and this noise is more disturbing for sleep than ventilation noise at similar sound levels.

The total sound level from ventilation equipment and traffic should be kept low outside bedroom windows. To protect from adverse effects on sleep quality indoor sound levels should not exceed LAeq,22-06 30 B and LAmax 45 dB, also when windows are kept slightly open.

Main results from the perception research
The perception research has shown that the present strategy to abate noise sources one at a time, mainly by trying to reduce the sound level of for example road traffic noise, is not enough for creating good soundscapes. A more effective strategy would be to plan for good soundscapes in developments and renewals of urban and suburban areas. This strategy must rely on residents’ perception of the whole soundscape, not only of singular sound sources. For this purpose new methods have been developed in this programme, which enables residents to characterize their perceived soundscapes in field as well as laboratory situations. These methods are sound-source identification, master scaling of soundscape loudness, and scaling of perceptual-emotional attributes.

Perceptual efficiency of noise shielding structures
Road traffic noise exposed façades (>50 dB LAeq,24h) would need much more efficient sound insulation in order to obtain acceptable indoor soundscapes. A good sound insulation at the shielded side of buildings gives a very large positive perceptual outdoor-indoor difference. A comparatively small effect is obtained by the same sound insulation at the noise-exposed side. To rely merely on the size of sound insulation in acoustic terms would thus result in insufficient mitigation of road traffic noise for obtaining good indoor soundscapes.

Specific findings from residents’ walks, listening to 30-s soundscapes were as follows. Outdoor-indoor sound level differences with windows closed were normal (LAeq,30s 30-35 dB) at road-traffic noise exposed sides. At the traffic-noise shielded sides the corresponding difference was slightly less (LAeq,30s 20-25 dB). Importantly, the size of these outdoor-indoor differences were reverse for residents’ perceived loudness of the soundscapes that is, less perceptual difference at the exposed side than at the shielded side (10-25 vs. 25-35 dB expressed as pink noise equivalent sound level during 30 s; PNE dB).

Moreover, differences in perceived loudness due to shielding buildings were found not to be well associated with corresponding differences in sound level. The exposed-shielded side differences in sound level were approximately 5 dB indoors with closed window, 10 dB with open window and 15 dB outdoors, all referring to LAeq,30s. Importantly, the size of the exposed-shielded differences in perceived loudness was similar but in completely reverse order, that is 15-20 dB indoors with closed window, 10-20 dB indoors with open window and 5-10 dB outdoors (expressed as pink noise equivalent sound level during 30 s; PNE dB).

Green labelling of soundscapes
Good soundscapes in urban areas are now possible to characterize with the aid of perceptual-emotional descriptors such as pleasant, soothing, eventful, stressful and monotonous. This new method makes it possible to diagnose and certify soundscapes in urban and suburban residential areas. The results show that shielding buildings give access to perceived soundscapes that are less adverse and dull (i.e., less annoying, loud, intrusive, etc.) and more soothing and pleasant than corresponding soundscapes at traffic-noise exposed sides of buildings. This is true indoors with closed windows, indoors with open windows and outdoors at the shielded side. Good outdoor soundscapes were, however, only found in residential areas with low road-traffic noise exposures (LAeq,24h <50 dB). In areas with significant road-traffic noise exposures (LAeq,24h >50 dB), good soundscapes could only be found indoors with closed windows at the shielded side of the building; nota bene not outdoors or indoors with open window at the shielded side.

A tentative “diagnostic” system for soundscape qualities was determined which differentiated soundscapes from exposed and shielded sides of buildings. It is based on results from similarity assessment of selected pairs of outdoor soundscapes. Multivariate analyses of perceived-soundscape similarities showed that three dimensions were sufficient for differentiating meaningfully the soundscapes: softness-loudness, eventfulness-monotonousness, and foreground-background. Visual inspection of color plots of the evolutionary spectra (“waterfalls”) of the acoustic soundscapes indicates an association among spectra in agreement with the similarity results. Thus, this multidimensional space may tentatively be utilized for diagnosing soundscapes.

Promising work has begun on a neural network model for “green” labeling of acoustic soundscapes grounded in a training set of perceived soundscapes. This model may give guidance in how optimise the acoustic soundscape with the aid of building locations, design of façades and use of materials for insulation and reflection. Such a model may be implemented as software and be made available for professionals involved in city planning, architecture, real estate agents, material production, etc. The neural network’s predicted perceived soundscapes may be “green” labeled in a diagnostic system of the kind described above. This research will continue in Phase 2 of this MISTRA programme.

Potential for modifying soundscapes
An active way to increase the access to quietness is to erect shielding buildings that fill existing gaps through which traffic noise penetrates and spoils the shielding effects.
The fact that the acoustic soundscape consists of two parts – the direct acoustic soundscape and the diffuse acoustic soundscape – has important consequences when attempting to change the acoustic soundscapes.

The main characteristic of diffuse acoustic soundscapes is the presence of a multitude of contributing noise sources, distributed over a wide area. It is difficult to control/modify a diffuse acoustic soundscape by traditional means of noise control. Screening will only lead to a redistribution of the sound; however consequences of such redistribution will not be recognised in a diffuse sound field. Redistribution of traffic flow can have a major effect on the directly exposed side, but only a minor effect in shielded areas.

Reducing sound pressure levels in shielded areas such as inner-yards can be achieved by adding acoustically absorbing areas along the transfer path between source and receiver, but especially inside the inner-yard.

Road coverings with (comparatively) low noise properties can be further developed. This is a special challenge in the Nordic countries due to the use of spiked tyres that destroy present types of drain asphalt. Technical progress in this area would enable a substantial increase of the fraction land area with reasonable quietness.

The soundscaping that is needed to achieve a major improvement of the environment demands actions on several levels.

The road network and the traffic planning on the regional level must be made with due consideration of the traffic noise. The importance of wide meshes in the main road network can not be over stressed. It has not only favourable effects from a soundscaping point of view.
It also promotes traffic safety.

The acoustic source strength of the traffic on high speed routes is so high that it severely limits the possibilities to achieve decent noise levels in the neighbourhood. Therefore, it is urgent to take quieter road surfaces into general use.

Also in the local road network, quiet road surfaces and wide meshes are essential. Wide meshes are positive for the noise situation and for traffic safety. However, it comes in conflict with desires of short distances between dwellings and parking. Further issues to consider are access for handicapped persons and security. New elements need to be considered in the solutions, such as different mesh size depending upon time on the day and enforcement of very low speed limits.

But also other means must be considered. The general speed limits must be set taking the problematic tyre/road-surface noise generation into account. Lower speeds give less noise and it is no technological problem to enforce lower speeds through external cruise control. The public resistance to such measures seems to be decreasing. Real obstacles when it comes to the possibilities to decrease tyre/road surface noise are the resistance from the tyre industry and the German attitude to speed limits.

Another method to reduce the acoustic source strength of the major roads is to use substantially higher and effectively sound absorbing barriers.

Through traffic inside potentially relatively quiet areas must be minimised and the remaining traffic calmed by methods that do not increase the noise. A running programme for development and regular use of best road surfaces each time road and street coverings are renewed should be a compulsory element in each local community’s action plan against noise. The traffic planning in its details is important.

Applying the research results in goal formulations for improving the acoustic environment
Guideline values for newbuilding of residential houses or significant rebuilding of traffic infrastructure, determined by the Swedish Parliament, [Swedish Government, Prop. 2000/01:130] are as follows:

- LAeq,24h, indoors with closed windows 30 dB

- LAmax, indoors at night with closed windows 45 dB

- LAeq,24h, outdoors, at façade 55 dB

- LAmax. outdoors, at “patios” 70 dB

The present goal formulation suffers from major deficiencies. Firstly, the goal does not correspond to a good environment. It might be referred to as an acceptable sound level in consideration of technical/economical difficulties. Secondly, the goal is not possible to reach at all dwellings within a foreseeable future, which creates a severe lack of political credibility. Thirdly, the goal is counter productive, because it can promote solutions that destroy quiet or relatively quiet areas. In order to reduce traffic noise levels in one street where the levels may be well over the guideline values, traffic may be moved to other streets without exceeding the guidelines there. In this way quietness may be destroyed and the number of annoyed people even increased.

Our results have demonstrated that the governing goals for plans at all levels and with different time horizons will be more cost/effective if expressed in terms of health and well-being instead of in terms of specific sound levels. Soundscaping opens new ways to achieve considerable improvements in health and well-being.

Quantified goals for 2010 as well as 2020 should, consequently, be formulated in health and well-being terms. Accurate methods to follow up such quantifiable goals must then be worked out. The results and experience from this Soundscape programme could be used for developing monitoring methods based upon measurement of annoyance. Such measurements would include the effects of actual sound levels, the influences of actual façade insulation and shields, the effects of actual access to quietness, the effects of more than one noise source, the effects of the actual road surfaces and real traffic speeds and distributions over time.

Prop. 2000/01:130 suggests that the outdoor-indoor sound level difference should be LAeq,24h 25 dB. Although this was potentially fulfilled in the building areas studied, residents’ perception of such differences was found to be much less at the exposed side, and of similar size only at the shielded side. More efficient noise protection would therefore be required at the exposed façade side in urban areas with LAeq,24h >50 dB.

Concluding statement
Our focus on the entire sound environment, not only one noise source at a time, has led us to believe that it is possible to introduce soundscaping as a strategic tool in city planning. The soundscape concept would then be utilised for creating positive and potentially restorative as well as quiet areas in the cities, including quiet sides of buildings. Such a future development would give soundscape support to health.