Luigi Maffei

The influence of visual characteristics of barriers on railway noise perception.

Noise annoyance is considered as the main effect of noise, it is a complex and multifaceted psychological concept dealing with immediate behavioral and evaluative aspects. In the last decades the research has intensely investigated the correlation between noise exposure and noise annoyance, nevertheless recent studies confirm that non-auditory factors influence the noise perception of individuals. In particular audio-video interaction can play a fundamental role. Today Immersive Virtual Reality (IVR) systems allow building laboratory test providing realistic experiences of the surrounding environment to detect more accurate information about the reactions of the local population. Regarding the interventions for environmental noise control the barriers represent the main solution; however some aspects related to their visual characteristic have to be further investigated. This paper presented a case study, where a sample of residents living close to a railway line assessed noise-related aspects for several barriers with different visual characteristics in an IVR laboratory test. In particular, three main factors were analyzed: the barrier type concerning the visibility of the noise source through the screen, the visual aspect of the barrier concerning some aesthetic issues and the noise level at the receiver concerning the acoustic performance of the barrier and the magnitude of the sound source. The main results of the ANOVA analysis showed that for transparent barriers Perceived Loudness and Noise Annoyance were judged lower than for opaque barriers; this difference increased as noise level increased.

The Effects of Vision-Related Aspects on Noise Perception of Wind Turbines in Quiet Areas

Preserving the soundscape and geographic extension of quiet areas is a great challenge against the wide-spreading of environmental noise. The E.U. Environmental Noise Directive underlines the need to preserve quiet areas as a new aim for the management of noise in European countries. At the same time, due to their low population density, rural areas characterized by suitable wind are considered appropriate locations for installing wind farms. However, despite the fact that wind farms are represented as environmentally friendly projects, these plants are often viewed as visual and audible intruders, that spoil the landscape and generate noise. Even though the correlations are still unclear, it is obvious that visual impacts of wind farms could increase due to their size and coherence with respect to the rural/quiet environment. In this paper, by using the Immersive Virtual Reality technique, some visual and acoustical aspects of the impact of a wind farm on a sample of subjects were assessed and analyzed. The subjects were immersed in a virtual scenario that represented a situation of a typical rural outdoor scenario that they experienced at different distances from the wind turbines. The influence of the number and the colour of wind turbines on global, visual and auditory judgment were investigated. The main results showed that, regarding the number of wind turbines, the visual component has a weak effect on individual reactions, while the colour influences both visual and auditory individual reactions, although in a different way.

Perspective of the soundscape approach as a tool for urban space design

In the last decade many improvements and large applications of noise control techniques have been observed, as well as enforcement and implementation of noise legislation at national and international levels. Notwithstanding, noise in urban areas has not decreased as expected and reductions in noise levels do not necessarily lead to a better acoustic comfort in urban areas. This has increased the concern of stakeholders (population, politicians, decision makers, �) and their awareness of the harmful effects of noise. The soundscape approach, concentrating on the way that people consciously perceive their environment (namely the interactions between people and sounds), might open novel perspectives and provide further insights towards fighting noise. In this approach, complementary to the noise control engineering techniques, the participation of people is fundamental along with their involvement that complies with the requirements issued by the European directive on the assessment and management of environmental noise. This paper provides an overview of some experimental studies carried out in the field and laboratory, dealing with urban areas of Naples and Rome with particular features (historical sites, outdoor markets, pedestrian areas, tourist attractions). Noise measurements and interviews of people by questionnaires have been used to investigate the sonic environment and its influence on the recognition and quality of a urban site by the users. A laboratory procedure based on virtual scenarios accompanied by visual and audio stimuli is presented and its potential as urban design tool is discussed

Steady-state air-flow and acoustic measurement of the resistivity of loose granular materials

In the course of a study for characterizing the acoustic properties of some loose granulates made of limestone chips, the authors have measured their resistivity in a very simple way by a steady-state air-flow technique. The results of these tests are compared with the corresponding values obtained by an acoustic technique. The latter relies on the assumption that at very low frequencies the real part of the normal-incidence flow impedance of a thin porous layer is very close to its steady-state air-flow resistance. The measurements results confirmed the above mentioned assumption to a certain degree. To the knowledge of the authors, no previous comparison of steady-state air-flow versus oscillating air-flow measurement of the resistivity of the considered granulates has been published yet.

The effect of vision on the perception of the noise produced by a chiller in a common living environment

Over the years, different noise sources related to community noise and their potential for eliciting noise annoyance have been investigated. Despite being a very common source within the urban realm, there is a current lack of literature on the perception of noise produced by small-medium sized sources like chillers and air conditioning devices. There are relatively few studies on the influence of audiovisual factors on noise perception for such sources. The main aim of this paper was to investigate the influence of the visibility of a chiller on perceived loudness and self-reported annoyance in a common indoor environment. Furthermore, this research aimed to investigate whether the abovementioned effects persisted in the presence of a cognitive task. To this purpose, two laboratory experiments were performed by means of an immersive virtual reality (IVR) system. Results show that the distance of the chiller influenced the noise perception, while the visibility of the chiller itself does not, assuming that a visual reference context is provided. Regarding the cognitive task, it was found to reduce the mean individual ratings of both the perceived loudness and noise annoyance related to the chiller, signifying that for the investigated sound source characterized by small spectral and temporal variation, it might have inhibited the attentional listening. These findings suggest that there is room for the implementation of recommendations for the design and management of such sources in the increasingly dense built environment.

Noise exposure in school gymnasia and swimming pools

School gymnasia and swimming pools are generally environments affected by poor acoustic conditions due to absence of sound absorbing materials, noisy sport activities, presence of many students at the same time and intensive use of blowing whistles to enforce the communication. The consequence is that physical education teachers can not only show long term stress but they can also be exposed to noise risk to noise-induced hearing loss. Investigation has shown that the problem is quite large; as many as 20�25% of physical education teachers can be affected by a noise exposure higher than acceptable limits. It is then necessary to analyze in detail all factors that can influence the noise in these special school environments in order to develop simple acoustical guidelines useful for school officials for stress management and hearing conservation programs.

Assessment of Large-Scale Action Plans to Reduce External Background Noise in School Buildings

In this paper the authors report on a simplified procedure, developed in a Geographical Information System (GIS) environment, for the localization of school buildings characterized by high indoor background noise levels due to the outside noise sources. The noise sources include road, rail, and air traffic and other human activities (playgrounds, commercial activities, etc). Starting with the knowledge of noise pollution levels in the urban areas where the educational premises are sited, indoor background noise levels are obtained by adding two corrective terms; the first term takes into account for road configuration sound attenuation and the second one for façade sound insulation. For each educational building, a priority index is assigned on the basis of fixed objective parameters. The developed procedure has been applied to case studies of school buildings in Naples. The procedure promises a practical, low cost tool for municipal administrations to assess critical educational buildings and to plan noise reduction measures.

Auditory recognition of familiar and unfamiliar subjects with wind turbine noise.

Considering the wide growth of the wind turbine market over the last decade as well as their increasing power size, more and more potential conflicts have arisen in society due to the noise radiated by these plants. Our goal was to determine whether the annoyance caused by wind farms is related to aspects other than noise. To accomplish this, an auditory experiment on the recognition of wind turbine noise was conducted to people with long experience of wind turbine noise exposure and to people with no previous experience to this type of noise source. Our findings demonstrated that the trend of the auditory recognition is the same for the two examined groups, as far as the increase of the distance and the decrease of the values of sound equivalent levels and loudness are concerned. Significant differences between the two groups were observed as the distance increases. People with wind turbine noise experience showed a higher tendency to report false alarms than people without experience.

Preliminary studies on the relation between the audio-visual cues' perception and the approaching speed of electric vehicles

For decades, quiet and zero emission vehicles have been considered the challenge for researchers and for the industry. Today, despite the great results obtained in the fields of air and noise pollution, the electric vehicles (EV) and hybrid electric vehicles (HEV) have raise an important question regarding the pedestrian safety. At the speeds permitted in urban areas (<50 km/h) these vehicles are considerably quieter than the traditional ones powered by gasoline or diesel. Nevertheless the amount of auditory cues associated to the approaching of these vehicles can be reduced. This can determine an increase of the risk of accidents for the pedestrians. Even though the recent studies on this problem are focused, mainly, on the minimum sound levels and on the spectral content of the approaching vehicles, further aspects of the semantic contents change of the event should be considered. In this paper a preliminary investigation on the relationship, and possible incoherence, among the approaching speed of the...

A lumped parameter model for the iterative analysis of cylinderlike antivibration mounts

It is known that wave effects in antivibration mounts result in differences between the force transmissibility, calculated for a one‐degree‐of‐freedom system having constant spring and dashpot parameters, and the experimentally measured one. An evaluation method which allows one to obtain the above mentioned parameters as functions of the frequency for simple rubber systems is presented. The method takes into account the high‐frequency interaction between the distributed mass and elasticity which is responsible for the wave effects in the mount. Some experimental evidence about the validity of the method is given.