Acoustic comfort evaluation in urban open public spaces

This paper presents the results of an intensive questionnaire survey and objective measurements on soundscape, aiming at the evaluation of acoustic comfort in urban open public spaces. From summer 2001 to spring 2002, 9200 interviews were made for four seasons in 14 urban open public spaces across Europe. The results suggest that the subjective evaluation of the sound level generally relates well with the mean L_eq, especially when the sound level is below a certain level, which is 73 dBA on the basis of this study. However, considerable differences have been found between the subjective evaluation of the sound level and the acoustic comfort evaluation: people tend to show more tolerance in terms of acoustic comfort evaluation. The background sound level has been found to be an important index in evaluating soundscape in urban open public spaces - a lower background level tends to make people feel quieter. Analyses of individual sound elements show that the acoustic comfort evaluation is greatly affected by the sound source type - introducing a pleasant sound can considerably improve the acoustic comfort, even when its sound level is rather high. No significant difference was found among different age groups in terms of subjective evaluation of a sound level, whereas in terms of acoustic comfort, there were significant differences.     

Non-auditory factors affecting urban soundscape evaluation

The aim of this study is to characterize urban spaces, which combine landscape, acoustics, and lighting, and to investigate people's perceptions of urban soundscapes through quantitative and qualitative analyses. A general questionnaire survey and soundwalk were performed to investigate soundscape perception in urban spaces. Non-auditory factors (visual image, day lighting, and olfactory perceptions), as well as acoustic comfort, were selected as the main contexts that affect soundscape perception, and context preferences and overall impressions were evaluated using an 11-point numerical scale. For qualitative analysis, a semantic differential test was performed in the form of a social survey, and subjects were also asked to describe their impressions during a soundwalk. The results showed that urban soundscapes can be characterized by soundmarks, and soundscape perceptions are dominated by acoustic comfort, visual images, and day lighting, whereas reverberance in urban spaces does not yield consistent preference judgments. It is posited that the subjective evaluation of reverberance can be replaced by physical measurements. The categories extracted from the qualitative analysis revealed that spatial impressions such as openness and density emerged as some of the contexts of soundscape perception.     

使用者的社会因素对地下商业街主观响度和声舒适度影响的调查研究

前人研究表明主观响度和声舒适度由实际环境中的众多因素决定,而不是仅受声压级的影响。本文在对地下商业街声场和声源特性进行调查与分析的基础上,针对使用者的社会因素对主观响度和声舒适度的影响,在哈尔滨的几个典型地下商业街进行了大量问卷调查,并运用相关统计方法对结果进行了分析。研究表明,收入和职业与主观响度存在相关性,相关系数在0.1～0.4之间,学历、收入和职业与主观声舒适度亦存在相关性,相关系数在0.1～0.6之间。虽然性别对主观响度和主观声舒适度无显著性影响,但是女性对这两者的主观感觉评分范围比男性宽。年龄段与主观响度和声舒适度的相关性不显著,但是不同地下商业街有的年龄段对主观响度和声舒适度的感受有区别。职业对于主观声舒适度的影响的本质是源于收入和学历对于主观声舒适度的作用,并且收入对于主观声舒适度的影响要大于学历的影响。这些结果可以增加对地下商业街声景的了解,并且为建立地下商业街声景预测模型提供了基础。     

Soundscape quality analysis by fuzzy logic: A field study in Cordoba,Argentina

This research studies urban soundscapes through the comparative analysis of twelve public open spaces in the city of Córdoba (Argentina), taken as case studies. The work aims to examine selection of indicators and assessment tools intended to characterize soundscape quality. The field study was carried out through surveys and acoustic and psychoacoustic indicators, that are used together to objectively describe the sound quality of urban spaces.     

Perceptual study of soundscapes in train stations

This paper presents a study on the perception of soundscapes in train stations. The two issues addressed by this study are (1) to show that people’s knowledge about the space typology that makes up a train station is also based on sound information, and (2) to show that this information is involved in the recognition of the type of space. This study is composed of two stages. In the first stage, two auditory experiments are performed on 66 soundscape samples recorded under natural conditions: (1) free categorization with verbalization and (2) forced-choice recognition. The statistical and lexical analysis of the first experiment reveals three main types of acoustical information: sound sources, human activities, and room effects. The results of the second experiment show that people were able to recognize the type of space (platform, hall, etc.) just by listening to its soundscape. Comparison between Experiments 1 and 2 reveals the auditory similarities of the soundscapes that were recognized as belonging to the same category. In the second step, an in situ questionnaire survey was carried out and confirms the laboratory results. Indeed, when travelers are asked to describe the soundscape of the space in which they are situated, they use the same kind of auditory similarities as those found in the experiments.     

Development of a 3D finite element acoustic model to predict the sound reduction index of stud based double-leaf walls

Building standards incorporating quantitative acoustical criteria to ensure adequate sound insulation are now being implemented. Engineers are making great efforts to design acoustically efficient double-wall structures. Accordingly, efficient simulation models to predict the acoustic insulation of double-leaf wall structures are needed. This paper presents the development of a numerical tool that can predict the frequency dependent sound reduction index R of stud based double-leaf walls at one-third-octave band frequency range. A fully vibro-acoustic 3D model consisting of two rooms partitioned using a double-leaf wall, considering the structure and acoustic fluid coupling incorporating the existing fluid and structural solvers are presented. The validity of the finite element (FE) model is assessed by comparison with experimental test results carried out in a certified laboratory. Accurate representation of the structural damping matrix to effectively predict the R values are studied. The possibilities of minimising the simulation time using a frequency dependent mesh model was also investigated. The FEA model presented in this work is capable of predicting the weighted sound reduction index R_w along with A-weighted pink noise C and A-weighted urban noise C_tr within an error of 1 dB. The model developed can also be used to analyse the acoustically induced frequency dependent geometrical behaviour of the double-leaf wall components to optimise them for best acoustic performance. The FE modelling procedure reported in this paper can be extended to other building components undergoing fluid–structure interaction (FSI) to evaluate their acoustic insulation.     

The relationship between traffic noise and insomnia among adult Japanese women

To clarify the relationship between traffic noise and insomnia, the authors conducted a survey and measured the actual sound level of noise in an urban area. Questionnaires were distributed to adult women who lived within 150 m from two major roads and were completed by 648 of the 1286 subjects (50.4%). The area was divided into three zones according to distance from the road (more than 50, 20-50 and 0-19.9 m). Fifty-seven subjects (8.8%) were classified as having insomnia. Average values of sound level at distances of 20, 50, and 100 m from the major road were L_eq 64.7, 57.1, and 51.8 dBA, respectively. Overall, there were no significant differences among the three zones in the prevalence of insomnia and no association between distance from the road and insomnia. However, the result from a sub-data set of the subjects who lived in the areas that showed decreasing noise level as the distance from the main road increased showed that distance from the road was associated with insomnia. This study suggests that researchers should consider the actual traffic situation and its sound level in epidemiological studies about the effects of traffic noise on insomnia.     

Wooden windows: Sound insulation evaluation by means of artificial neural networks

Windows are the weakest part of a façade in terms of acoustic performance: the weighted sound insulation index (R_w), measured according to ISO 140-3, is the fundamental parameter to evaluate the façade acoustic insulation.The paper aims at developing an artificial neural network (ANN) model to estimate the R_w value of wooden windows based on a limited number of windows parameters; this is a new approach because acoustic phenomena are non-linear and affected by a plurality of factors and, therefore, usually investigated through experimentation.Data set is taken from experimental campaigns carried out at the Laboratory of Acoustics, University of Perugia. A multilayer feed-forward approach was chosen and the model was implemented in MATLAB. On the basis of the results obtained by means of a preliminary training and test campaign of several ANN architectures, five main parameters were selected as network inputs: window typology, frame and shutters thickness, number of gaskets, R_w of glazing; R_w value of the window is the network output. Different ANN configurations were trained and a root mean-square error less than 3% was obtained, comparable to measurement uncertainty.This approach allows to develop a model which, with input parameters varying within appropriate ranges, can easily estimate the acoustic performance of wooden windows without experimental campaign on prototypes, saving both money and time. If the training data set is large enough, the presented approach could be very useful for design and optimization of acoustic performance of new products.     

Towards standardization in soundscape preference assessment

The study of soundscapes involves diverse fields of practice, diverse approaches and diverse disciplinary interests. The field overlaps with the much larger and established field of environmental noise management, and also intersects, to various degrees, with other areas of acoustics such as sound quality, human acoustic comfort in buildings, and music—and also with non-acoustic fields such as wilderness and recreation management, urban and housing design, and landscape planning and management. Working Group 54 of ISO/TC 43/SC 1 has been formed with a remit of standardization for perceptual assessment of human sound preference (in outdoor space) using questionnaires. The working group began its work in 2009, with considerable and wide-ranging discussion amongst its members. This paper makes a range of observations, and sometimes suggestions, on matters pertinent to eventual definition of the soundscape; on outcomes of interest arising from experience of a soundscape; on the role of context in assessment; on sound sources in different places; and on relevant lessons for soundscape assessment from experience of questionnaire measurement of noise annoyance. It represents a personal view, though informed by a range of opinions from the Working Group meeting and from literature.     

Evaluation and analysis of the environmental noise of Messina, Italy

In this paper, the results of a study on the environmental noise pollution of the city of Messina (Italy) are presented. The investigation has included a preliminary classification of the territory in six acoustically homogeneous areas according to Italian noise regulations. On the basis of the resultant acoustic zoning 35 sites were selected for an experimental survey. This last has been carried out by extensive measurements of the main indexes for noise pollution (L_eq, L₁, L₁₀, L₅₀, L₉₀, L₉₉) and of the traffic flow and composition. Results indicate that: (a) main roads of Messina are overloaded by traffic flow during day-time period and that in all the examined sites daily average sound levels due to road traffic exceed environmental standards by about 10 dBA; (b) environmental noise exhibits a certain degree of spatial variance resulting primarily from the peculiar geo-morphological structure of the town and from the transport infrastructure and (c) more than 25% of residents should be highly disturbed by road traffic noise.     

Predominant environmental noise classification over sound mixing based on source-specific dictionary

This paper presents a methodology to classify predominant urban acoustic sources in real mixed signals. This is based on a source-specific dictionary with atoms in the time–frequency domain using the Orthogonal Matching Pursuit (OMP) algorithm and identifying the class through a proposed selection criterion with a dynamic number of iterations involving a lower algorithm complexity. Several time–frequency atoms were evaluated considering retained energy and relative error to build a source-specific dictionary in the relevant classes. The source-specific dictionary has better results up to 7% in retained energy than to use an individual dictionary such as based on wavelet or Gabor functions, improving classification of predominant sources over sound mixing up to 9% compared to using standard dictionaries. Experimental results on classification are applied to mixture inter-class signals of two or more sources recorded by a real permanent monitoring system in an urban soundscape. The classification performance has successfully achieved identifying a predominant source in real inter-class mixtures of urban soundscapes.     

Comments on “variational equations for thin elastic shells”

A further study consisting of acoustic and subjective measurements of 552 Chinese firemen at 12 fire stations in Hong Kong has been carried out. Annoyance with aircraft and traffic noise conditions, as expressed by the firemen, was found to correlate well with the acoustic measurements. For aircraft noise the correlation of annoyance with the Number and Noise Index (NNI) was slightly better than with the dB(A) peak value. For traffic noise the similar correlation with the mean sound pressure levels which exceeds 10 % of the sampling period (L₁₀) was slightly better than with the Noise Pollution Level and the Traffic Noise Index. The correlation of the arousal due to the aircraft and traffic noise was similarly found to depend on the NNI and L₁₀ values. However, traffic noise was responsible for more disturbance than aircraft noise. The study demonstrated the desirability of adopting indoor acoustic measurements instead of outdoor measurements for any survey of this kind.     

Estimation of the long term average sound level from hourly average sound levels

It is shown how to estimate the long-term average sound level, L_AeqLT (for free flowing road traffic) from measurements of the hourly A-weighted equivalent sound level, L_Aeq1h. To estimate the parameters of the model which describe noise emission and attenuation, concurrent measurements of L_Aeq1h at two distances from the considered road are needed. A semi-empirical formula is derived for L_AeqLT approximation. Also the uncertainty of this approximation is given as a function the distance from the road and receiver height.     

Temperature-dependent Brillouin scattering studies of surface acoustic modes in Nd0.5Sr0.5MnO3

Brillouin scattering experiments are carried out to study the surface acoustic waves in Nd_0.5Sr_0.5MnO₃ as a function of temperature in the range of 40-300 K covering the metal-insulator and charge-ordering phase transitions. The surface modes include surface Rayleigh wave, pseudo-surface acoustic wave (PSAW) and high velocity PSAW. The observed softening of the sound velocities for the surface modes below paramagnetic to ferromagnetic transition, T_c is related to the softening of the C₄₄ elastic constant. The subsequent hardening of the sound velocity below the charge ordering transition temperature T_co is attributed to the coupling of the acoustic phonon to the charge ordered state via long range ordering of the strong Jahn-Teller (JT) distortion.     

EXPERIMENTAL STUDY OF NOISE PRODUCED BY STEADY FLOW THROUGH A SIMULATED VASCULAR STENOSIS

An in vitro experiment is carried out in order to study the acoustic effects of a vascular constriction (stenosis) in people and provide correlations between these effects and parameters relevant to the hydrodynamic and acoustic processes. For this purpose, we measure the sound produced when water flows through an elastic tube which is either unobstructed or contains a rigid axisymmetric constriction. The sound is measured at the outside of a large annular container filled with water and bounded at the inside by the coaxial elastic tube. The analysis of the acoustic fields shows that a stenosis has two basic acoustic effects. These are a general increase in the sound level and the production of a number of additional distinct peaks (new frequency components) in the acoustic power spectrum. The frequencies of these peaks are close to the characteristic frequencies of vortex formation in the disturbed flow region behind a stenosis and the resonance frequencies of vibration of the post-stenotic segment of the tube. Another important result is that the stenosis generated acoustic power is approximately proportional to the fourth power of the stenosis severity and the same power of the flow Reynolds number.     

A study of the accuracy of mobile technology for measuring urban noise pollution in large scale participatory sensing campaigns

The study reports on the relevancy and accuracy of using mobile phones in participatory noise pollution monitoring studies in an urban context. During one year, 60 participants used the same smartphone model to measure environmental noise at 28 different locations in Paris. All measurements were performed with the same calibrated application. The sound pressure level was recorded from the microphone every second during a 10-min period. The participants frequently measured the evolution of the sound level near two standard monitoring sound stations (in a square and near a boulevard), which enables the assessment of the accuracy and relevancy of collected acoustic measurements. The instantaneous A-weighting sound level, energy indicators such as L_A,eq, L_A10, L_A50 or L_A90 and event indicators such as the number of noise events exceeding a certain threshold L_α (NNEL ? L_α) were measured and compared with reference measurements. The results show that instantaneous sound levels measured with mobile phones correlate very well (r > 0.9, p < 0.05) with sound levels measured with a class 1 reference sound level meter with a root mean square error smaller than 3 dB(A). About 10% of the measurements for the boulevard location (respectively 20% for the square) were inaccurate (r < 0.3, p < 0.05). Nevertheless, mobile phone measurements are in agreement for the L_A50 and the L_A90 acoustic indicators with the fixed station (4-m high) measurements, with a median deviation smaller than 1.5 dB(A) for the boulevard (respectively 3 dB(A) for the square).     

Relationship between sound insulation performance of walls and word intelligibility scores

Conversations must be shielded from people in an adjacent room if they include confidential information. Word intelligibility tests were performed in a total of 185 sound fields to examine the relationship between sound insulation performance and the degree of conversation leakage. The parameters of the test sound fields were background noise level in the adjacent room and the level difference between the two rooms. The background noise level was varied from 30 to 50 dB (A-weighted). The level difference was parametrically varied in terms of eight frequency characteristics and 10 absolute values. The results showed that word intelligibility scores were strongly correlated with the A-weighted speech-to-noise ratio and SNR_uni32. Equal-intelligibility contours, which can easily show the weighted level difference and A-weighted background noise level required to achieve a certain level of word intelligibility scores, were obtained from a multiple logistic regression analysis.     

Urban ambient outdoor and indoor noise exposure at home: A population-based study on schoolchildren

To investigate residential exposure to environmental noise among children in an urban area, a noise measurement campaign was performed at the residences of 44 schoolchildren. Outdoor and indoor noise levels were simultaneously recorded during one week inside and outside each child’s bedroom and in the other room where each child spent most of his or her time, called “the main room”. Associations between equivalent noise levels and familial or environmental characteristics were explored.The recorded equivalent continuous sound levels (L_Aeq) were prone to large variability between dwellings regardless of the measurement location and time of day. Factors linked to outdoor noise level differed from those associated with indoor noise level. Indoor noise levels were associated with the number of children present and noise sources present in the dwelling, whereas outdoor L_Aeq depended significantly on the socio-economic status (SES) of the household. An association was found between the type of view from the window and outdoor L_Aeq, but no significant association was observed between view from the window and indoor L_Aeq. These results support a complex link between noise exposure and the characteristics of the dwelling and of the family, and highlight the contribution of the indoor noise sources to the ambient noise level.Considering the observed acoustic levels and their variability, the sensitivity of children to noise, and the length of time they spend at home, research efforts are needed to better quantify noise exposure at home if the actual burden of noise on child health is to be identified.