This paper outlines an approach for obtaining microphone array geometry for use in traffic noise analysis. The designed array has a smaller number of microphones compared to existing solutions, thereby reducing the cost of system realization. The array geometry is irregular, consists of 24 microphones, and was obtained by an optimization procedure that minimizes beampatterns sidelobes. Microphone position optimization was performed in the frequency band from 300 Hz to 2000 Hz, defined by traffic noise characteristics. The designed array is used in ongoing research dedicated to the analysis of angular distribution of incident traffic noise sound energy impeding a facade in urban environment.

This study presents the analysis of statistical parameters of the output quantisation noise amplitude distribution in the analogue-to-digital converter (ADC) with oversampling and decimation. Hypothesis was tested that quantisation noise amplitudes on the output of the system have a Gaussian distribution. To test this hypothesis, Chi-squared statistical test was performed with parameter estimation based on grouped data. Simulation models were made for two types of ADCs: classical bbit and sigma-delta. Various realisations of decimation filters were used as well as various values of the decimation factor. Based on the number of cases in which the hypothesis was rejected, the significance of the test was determined, i.e. the deviation from the ideal Gaussian distribution was quantified. Results of this research can prove to be useful in system design process, where accurate knowledge of the quantisation noise statistical model parameters is required. This study presents general procedure for analysing the amplitude distribution of the quantisation noise, which can easily be implemented on other modified models of the ADC with oversampling.

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This paper presents preliminary results of a research dedicated to noise analysis at the building envelope using microphone arrays. Motif for such a research is a dependence of façade elements insulation characteristics on incident angles of noise impeding a façade. The goal is to determine the influence of different building and street configurations on the discrepancies between laboratory and in-situ values of façade elements sound insulation, and develop a model for predicting in-situ façade performances depending on building surroundings. Microphone array mounted on a façade can provide an insight into impeding noise energy distribution over angles of arrival. This distribution is examined for a number of different scenarios, including buildings in canyon and non-canyon streets, different mounting heights of the array, different widths of streets etc. Planar array consisting of 24 microphones with a diameter of 2.2 m is used for measurements. Results for given scenarios are presented and compared with a discussion on building surroundings influence on the performances of their façade elements.

Decimation is a frequently used technique in audio signal processing. This paper investigates the influence of the values of stopband attenuation of decimation filters on the subjective perception of resulting audio signals. In practice, the demands for stopband attenuation of these filters are quite rigorous. The paper examines how justified these demands are from the psychoacoustic point of view. Basic procedure within such a research is a subjective test. Aside from objective parameters, the subjective evaluation is a method that can give insight into the characteristics of audio signal processing under testing. Results of subjective testing of the influence of different values of stopband attenuation on the perceptibility of interfering signal are presented for various audio signals. Two types of interfering signals were used in the subjective test. To increase the validity of psychoacoustic test, the probability of false detection of differences is measured by presenting subjects with equivalent signals. The results of subjective testing can prove to be useful in the design process of decimation filters for audio system applications.