Texture and noise features for road pavement identification and classification

Road planners and road administrators frequently face the problem of insufficient knowledge of the correlation between the type of road surface and the resulting noise emission. The aim of this research is to establish the relationship between road surface characteristics, such as macrotexture, and tire/pavement noise emission, in order to identify and classify road surfaces by using statistical learning methods, which is a non-destructive approach. For this purpose, several road sections with different pavement types were selected and tested. The Close-Proximity (CPX) method was adopted, as it is commonly used to register the traffic noise in near field conditions. In its turn, macrotexture of each surface was provided by a high speed profilometer, which is one of the parameters required for the assessment of the performance and conformity of road pavements. The set of features extracted from the noise emission profile and from the surface texture was applied to a statistical classifier for evaluation. A correct identification of the road pavement leads to better data, thus enhancing the accuracy of road noise predictions. Results are presented and discussed.(undefined

Biological control of Prays Oleae (BERN.) By chrysopids in tras-os-Montes region (Northeastern Portugal)

A study was carried out in an olive grove in the Tras-os-Montes region, in the period 1993 to 1996 to establish the rate of predation of chrysopids on Prays oleae (Bern.) eggs. Data on a trial conducted in 1996 to evaluate the effectiveness of field releases of Chrysoperla carnea (Steph.) in controlling eggs of the carpophagous generation of the pest are also reported. Six species of Chrysopidae have been collected. The most abundant were C. carnea and Mallada flavifrons (Brauer) which together represented about 74% of total captures. The main period of adult catches occurred between July and October. The rate of predation by chrysopids on P. oleae eggs varied among different generations of the pest and in different years, reaching 34% for the carpophagous generation in 1996. The potential damage that might be expected from the studied population of P. oleae was almost halved by releasing 360 larvae of C. carnea per tree.PAMAF lED no 611

A hybrid MLS technique for room impulse response estimation

The measurement of room impulse response (RIR) when there are high background noise levels frequently means one must deal with very low signal-to-noise ratios (SNR). if such is the case, the measurement might yield unreliable results, even when synchronous averaging techniques are used. Furthermore, if there are non-linearities in the apparatus or system time variances, the final SNR can be severely degraded. The test signals used in RIR measurement are often disturbed by non-stationary ambient noise components. A novel approach based on the energy analysis of ambient noise - both in the time and in frequency - was considered. A modified maximum length sequence (MLS) measurement technique. referred to herein as the hybrid MLS technique, was developed for use in room acoustics. The technique consists of reducing the noise energy of the captured sequences before applying the averaging technique in order to improve the overall SNRs and frequency response accuracy. Experiments were conducted under real conditions with different types of underlying ambient noises. Results are shown and discussed. Advantages and disadvantages of the hybrid MLS technique over standard MLS technique are evaluated and discussed. Our findings show that the new technique leads to a significant increase in the overall SNR. (C) 2008 Elsevier Ltd. All rights reserved

Avaliação do ruído de tráfego rodoviário em pavimentos com camadas de desgaste delgadas

O ruído produzido pelo tráfego rodoviário, sendo uma componente importante de poluição ambiental que afecta significativamente as populações, foi incluído no conjunto de indicadores de desempenho dos pavimentos. No entanto, a informação existente quanto ao impacte ambiental dos diferentes tipos de camadas de desgaste utilizadas correntemente em Portugal é escassa, de modo a não ser possível fazerem-se considerações ao nível da gestão dos pavimentos, particularmente no que respeita às estratégias de reabilitação. Neste artigo faz-se a comparação do nível de ruído (Lmax) em diversos pavimentos com camadas de desgaste delgadas adoptadas actualmente na reabilitação funcional de pavimentos. O nível de ruído dos veículos ligeiros é obtido pelos métodos da passagem controlada (CPB) e da proximidade imediata (CPX). A metodologia utilizada foi a preconizada nas normas ISO 11819-1:1997 e ISO CD 11819-2. Em ambos os métodos, as camadas delgadas apresentam níveis de ruído reduzidos relativamente às camadas convencionais

Towards noise classification of road pavements

Noise classification of road surfaces has been addressed in many European countries. This paper presents the first approach towards noise classification of Portuguese road pavements. In this early stage, it aims at establishing guidelines for decision makers to support their noise reduction policies and the development of a classification system adapted to the European recommendations. A ranking to provide guidance on tire-road noise emission levels for immediate use by decision makers, road authorities, contracting parties and environmental officers will be established. This research was based on the results provided by three early studies covering more than ten different surfaces, among which, rubberized asphalt and experimental non conventional surfaces with optimized grading. On each road trial, the tire-road noise generated by light vehicles and heavy trucks at three speed levels were measured by means of the Controlled Pass-By method (CPB). Three of these runs were also tested by the Close ProXimity method (CPX). Additionally, tests to characterize texture and skid resistance were performed. The early noise classification studies of road pavements focused only on the CPB tests. Three groups with similar acoustical performance were identified. Noise level abatements of about 10 dB were achieved for the gap graded mixtures with a maximum aggregate size inferior to 10 mm

Avaliação do ruído de tráfego : metodologia para a caracterização de camadas de desgaste aplicadas em Portugal

Uma das consequências do desenvolvimento económico verificado nas últimas décadas é o aumento significativo do tráfego rodoviário. O ruído induzido pelo tráfego é um importante factor de poluição ambiental que afecta cada vez um maior número de pessoas. Nesta comunicação efectua-se a comparação do nível de ruído (Lmax) registado para os veículos ligeiros, e pesados, de acordo com o método estatístico de passagem (SPB), e para os veículos ligeiros sugundo o método de passagem controlada (CPB) e o método da proximidade imediata (CPX) em trechos piloto. Usam-se os métodos SPB e CPX como preconizado nas normas ISO 11819-1:1997 e ISO CD 11819-2. Quanto ao método CPB, foi usada uma adaptação do método SPB com veículos seleccionados. Neste caso foram realizadas 4 passagens × 4 velocidades (50, 80, 100 e 110 km/h) ×4 veículos (2 ligeiros, 1 4×4, 1 carrinha). Apresentam-se os resultados obtidos por cada um dos métodos, por forma a definir a metodologia mais adequada para a caracterização de camadas de desgaste de pavimentos em serviço em Portugal, tendo em conta o tipo de via de tráfego e as respectivas velocidades legais de circulação

Silent surfaces : an experience in Portugal

It is acknowledged that traffic noise affects human behaviour and health. Measures aiming at mitigating the impact of traffic noise are not always viable in urban areas. In Portugal, road designers have recently started to consider silent surfaces as alternative within their road pavement projects. In this paper the tire-surface noise of three surface layers integrated in a rehabilitation project carried out in an urban road that carries more than 40000 vehicles per day is assessed: i) one dense asphalt layer with limited maximum aggregate size, following the SILVIA recommendations for low noise surfaces; ii) two very-thin surfaces with different grading, which are an adaptation of the very-thin layers widely used in France to Portuguese conditions. The surface layers were constructed consecutively, involving segment lengths with more than 500 m. The surface texture was measured using a high speed profilometer. Skid resistance was also measured. The noise level was measured both by pass-by tests with selected traffic (trucks and light vehicles) at several speeds and by close proximity tests. The thin layers tested provided very good noise reduction values, especially at high speeds, and had a better performance than gap graded asphalt rubber surfaces frequently used in Portugal

Técnica híbrida segmentada ponderada aplicada à estimação de parâmetros acústicos de salas (Hibrid Segmented Swept Sine)

A aplicação da técnica de Varrimento Sinusoidal Logarítmico - Swept Sine - aplicada à acústica de salas tornou-se usual devido à sua elevada SNR e robustez contra pequenos valores de não-linearidades e variância no tempo da sala em teste. No entanto, a presença de fontes de ruído não estacionário, por exemplo presença de pessoas na vizinhança, ruído de génese viária ou ainda ruído proveniente do decorrer das actividades de espectáculo pode implicar um valor de SNR baixo para uma correcta estimação dos parâmetros acústicos. Este tipo de ruído apresenta grandes flutuações de energia ao longo do tempo e da frequência. Este estudo explora esta característica no sentido de permitir um aumento da SNR no final do processamento. A técnica Hibrid Segmented Swept Sine consiste em enviar para a sala com um conjunto de M tramas Swept Sine. Cada trama é dividida em N segmentos e onde cada segmento é analisado por bandas de frequência através da aplicação de um banco de filtros, ou seja, é feita uma análise fina da energia nos domínios do tempo e da frequência. A partir das energias obtém-se uma função de ponderação no tempo e na frequência que é aplicada às tramas utilizando de seguida a técnica de médias temporais. Testes realizados para vários tipos de sinais de ruído revelaram incrementos significativos da SNR. A técnica Híbrida de Segmentação Ponderada mostrou que, para determinados tipos de sinal de ruído, existem incrementos de SNR superiores a 15 dB (ruído do tipo fala) em relação à técnica Swept Sine.info:eu-repo/semantics/publishedVersio