# Optimized Sensors Network and Dynamical Maps for Monitoring Traffic Noise in a Large Urban Zone
## 2 State of the Art
### Related Works Relevant to the Dynamap Project  
The classification of streets plays an important role for Dynamap. Different attempts are known, and we refer to a few of them. A street categorization has been developed for the city of Valladolid (Spain) [13], and an urban noise functional stratification has been studied for estimating average annual sound level [14]. Closely related to this issue is the problem of identifying the type of vehicle producing the noise, e.g., vehicle sound signature recognition by frequency vector principal component analysis [15], a dimensionality reduction approach for detection of moving vehicles [16], techniques of acoustic feature extraction for detection and classification of ground vehicles [17], noise source identification with Beamforming in the pass-by of a car [18], a scaling model for a speed-dependent vehicle noise spectrum [19], and a vehicle speed recognition from noise spectral patterns [20]. Health related issues due to traffic and environmental noise has attracted a great deal of attention over the years. Annoyance issues due to the transportation and their relationships with exposure metrics have been studied [21]. A study of some effects of aircraft noise on cognitive performance in schoolchildren has been reported [22], as well as the relation between ambient noise and cognitive processes among primary schoolchildren [23]. Noise and mental performance quantified by personality attributes and noise sensitivity have been considered [24], in addition to the important issue of traffic noise and risk of myocardial infarction [25]. Of prime importance is also the relation between environmental noise, sleep, and health, as discussed in [26]. Long-term road traffic noise exposure is also associated with an increase in morning tiredness [27]; in addition, transportation noise resulted in increased blood pressure in adults [28]. Further work includes the exposure modifiers of the relationships of transportation noise with high blood pressure and noise annoyance [29], the quantitative relationship between road traffic noise and hypertension from the point of view of meta-analysis [30]. A recent, updated study on health-related issues of noise has been published by the WHO [2]. From a larger geographical perspective, there is interest in the environmental burden of disease in Europe by assessing risk factors in some countries [31], also yielding an international scale implementation of the CNOSOS-EU road traffic noise prediction model for epidemiological studies [32]. This can be extended to a global noise score indicator for classroom evaluation of acoustic performances in the LIFE GIOCONDA project, allowing a comparison between different classrooms or schools, based on their acoustic performances, and a homogeneous evaluation of the priority for planning noise mitigation actions in Italian schools [33]. Research has been performed to suggest a selection of suitable alternatives to reduce the environmental impact of road traffic noise using a fuzzy multi-criteria decision model [34]. Annoyance evaluation has been performed due to overall railway noise and vibration in Pisa (Italy) urban areas, showing the limitations of traditional noise mapping for railway epidemiological studies based exclusively on ordinary transits, thus confirming the role of vibrations as enhancing factor for disturbance [35]. A laboratory study has been reported on noise annoyance assessment of various urban road vehicle pass-by noises in isolation and combined with industrial noise [36]. A survey on exposure-response relationships for road, rail, and aircraft noise annoyance, and the differences between continuous and intermittent noise have been considered [37]. The application of the intermittency ratio (IR) metric for the classification of urban sites based on road traffic noise events has been studied and proved to be a useful supplementary metric to the equivalent level, which measures only the energy content of the noise exposure [38].