The accurate estimation of the acoustical parameters of a space to be used by people, such as theaters, concert halls, conference rooms, sport stadiums, and other public areas, implies that the measurements should be evaluated in the presence of an audience. However, for reasons of annoyance, people are usually avoided and a correction factor related to the effective absorption of the audience area is applied to the results only. This procedure does not take into account the variability of some parameters such as the relative humidity during the event, which influences considerably the magnitude frequency response. The swept sine technique is very attractive in acoustical measurements due to the high signal-to-noise ratios (SNR) and robustness against nonlinearity of the measurement chain and time variance. The use of some convenient music tracks in agreement with the perceptual masking effect minimizes the annoyance and increases the SNR simultaneously. The sinusoidal synthesis algorithm is applied to some parts of the music. After questioning a set of persons, some results based on an annoyance indicator are presented giving advantages and disadvantages of this method.
Studies of the impact of noise from Fortaleza International Airport, located well within the urban area, based on the noise mapping project that was created for the spatial representation of indicators of ambient noise in the city of Fortaleza, Brazil, which provided a tool essential to analyze and define strategies for the control of noise pollution in the city. This is the first noise map drawn to scale in a large city in Brazil. Noise emissions from major sources that contribute to the sound environment of the city, including road traffic, railway noise, aircraft noise, industrial noise, noise and entertainment areas were included. The method followed a hybrid approach, essentially calculating complemented with experimental measurements for validation and calibration. The study of airport noise allowed detailed results for equip lawsuit against the noise produced during operation of the airport.
The swept sine technique is very popular for the measurement of room impulse response due to its large signal-to-noise ratio (SNR) and immunity against subtle time-variance and nonlinearity of the room under test. However, the acoustical measurements in the presence of high background noise levels leads usually to unsatisfactory results. For situations of high level nonstationary noise, the mean square of the overall sequence must be minimized in order to increase the SNR. The new technique named segmented swept sine consists in exciting the room with a set of M swept sine signals with application of a dedicated weighting average method and a noise pattern recognition procedure. Each swept sine signal is segmented followed by the estimation of the mean square (MS) value of the respective segment. A weighting procedure is applied to each segment according to the MS value and the likelihood between them. The average technique is then applied. This procedure ensures that the resulting swept sine signal has the highest SNR value. Several examples are presented to compare the standard swept sine and the segmented swept sine techniques, giving advantages and disadvantages of each technique.
Com cerca de 1,4 milhão de habitantes, a cidade de Belém localiza-se no norte do Brasil, na região conhecida como Amazônia brasileira. Esta cidade tropical possui belos parques públicos urbanos construídos no início do século XX, que recebem um número grande de visitantes em busca de recreação e lazer. Estes parques, inicialmente circundados por residências térreas, hoje se encontram em meio a grandes centros comerciais, de serviço e arranha céus, onde uma parcela da população brasileira passou a residir, como impacto da urbanização no país. As paisagens sonoras de quatro parques públicos com diferentes tipologias, dois deles de acesso livre nas 24 horas e outros dois com visitação controlada, são aqui analisadas. As medições sonoras efetuadas indicam uma forte influência do tráfego rodoviário, de obras de construção civil e atividades recreativas em suas paisagens sonoras, enquanto os usuários identificam sons de pássaros, vento nas árvores, natureza e tranquilidade. Estes resultados aparentemente opostos, mas na verdade complementares, envolvendo variáveis físicas e psicológicas, são apresentados e discutidos neste artigo. Estes resultados representam uma contribuição brasileira aos estudos de paisagens sonoras urbanas e de “quiet areas”, que vêm se desenvolvendo com menor frequência em países como o Brasil. Trata-se, ainda, de importante ferramenta de apoio ao planejamento urbano das cidades brasileiras, em especial às intervenções em seus parques públicos visando valorizar as componentes sonoras de suas paisagens.
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