J. L. Bento Coelho

Statistical classification of road pavements using near field vehicle rolling noise measurements

Low noise surfaces have been increasingly considered as a viable and cost-effective alternative to acoustical barriers. However, road planners and administrators frequently lack information on the correlation between the type of road surface and the resulting noise emission profile. To address this problem, a method to identify and classify different types of road pavements was developed, whereby near field road noise is analyzed using statistical learning methods. The vehicle rolling sound signal near the tires and close to the road surface was acquired by two microphones in a special arrangement which implements the Close-Proximity method. A set of features, characterizing the properties of the road pavement, was extracted from the corresponding sound profiles. A feature selection method was used to automatically select those that are most relevant in predicting the type of pavement, while reducing the computational cost. A set of different types of road pavement segments were tested and the performance of the classifier was evaluated. Results of pavement classification performed during a road journey are presented on a map, together with geographical data. This procedure leads to a considerable improvement in the quality of road pavement noise data, thereby increasing the accuracy of road traffic noise prediction models.

Lambertian Enclosures — A First Step towards Fast Room Acoustics Simulation

A statistical method for calculation of the acoustical parameters of lambertian enclosures (that is, enclosures with diffusely reflecting boundaries) is presented. The theory considers the distribution of sound particles over the boundaries of the enclosures. The method includes the familiar Kuttruff Integral Equation. A homogeneous Markov Chain of first order is obtained through the time discretisation of the equations. Applications of this method are demonstrated for the case of a long enclosure and for the case of a real-shaped room. Decay calculations as well as steady-state sound distributions are obtained. The results show that the method is reliable, flexible, and that computation times are low.

An assessment of the simulation and auralization quality of the Virtusound platform

The Virtusound platform was developed for real time room acoustics simulation and auralization through binaural technology. The calculation module uses an accelerated mirror image source method and a time-dependent radiosity method for the computation of the binaural room impulse responses. Informal tests have shown the system to be accurate and the rendered tri-dimensional sound to be quite realistic. However, a more comprehensive assessment was seen to be required in order to guarantee the quality of the platform. This paper presents therefore a first assessment on the capabilities of the Virtusound system in terms of the predicted objective parameters and in terms of the produced auralizations.

The Fortaleza noise mapping project: A tool for the definition of noise action plans for the airport, the light rail system, and the Ceara musical event.

The Fortaleza noise mapping project was set up for the spatial representation of environmental noise indicators to obtain an essential tool to analyze and define strategies for noise pollution control in Fortaleza, Brazil. This is the first large‐scale noise map drawn for a large city in Brazil. Noise emissions from the most important sources contributing to the sound environment of the city, namely, road traffic, railway noise, aircraft noise, industrial noise, and noise from entertainment areas, were included. The method followed a hybrid approach, essentially calculation complemented with experimental measurements for validation and calibration. The large‐scale noise assessment allowed detailed studies of the noise impact of the Fortaleza International Airport, located well within the urban city area, the impact of the passage of the underground access light rail tunnel on the local soundscape, and the impact of the Ceara musical event, which, though being part of the city cultural program, takes place...

Acoustic Modelling and Measurements of Engine Mufflers

Most buildings such as hospitals, hotels, governmental offices, data processing rooms, etc, are equipped with internal combustion engines, diesel motors and generators to supply energy in emergencies. These same IC engines are used for industrial applications, building services and transportation. Exhaust noise are the predominant noise source with most internal combustion engines and thus exhaust systems incorporating mufflers have been designed to reduce the noise. This paper describes the analysis of several configurations of mufflers and also presents comparisons between the results for the transmission loss obtained by numerical modelling (FEM), Transfer Matrix Method (TMM) and measurements.