Clustering outdoor soundscapes using fuzzy ants

A classification algorithm for environmental sound recordings or "soundscapes" is outlined. An ant clustering approach is proposed, in which the behavior of the ants is governed by fuzzy rules. These rules are optimized by a genetic algorithm specially designed in order to achieve the optimal set of homogeneous clusters. Soundscape similarity is expressed as fuzzy resemblance of the shape of the sound pressure level histogram, the frequency spectrum and the spectrum of temporal fluctuations. These represent the loudness, the spectral and the temporal content of the soundscapes. Compared to traditional clustering methods, the advantages of this approach are that no a priori information is needed, such as the desired number of clusters, and that a flexible set of soundscape measures can be used. The clustering algorithm was applied to a set of 1116 acoustic measurements in 16 urban parks of Stockholm. The resulting clusters were validated against visitor's perceptual measurements of soundscape quality

Presence of 1/f noise in the temporal structure of psychoacoustic parameters of natural and urban sounds.

1/f noise or pink noise, which has been shown to be universal in nature, has also been observed in the temporal envelope of music, speech, and environmental sound. Moreover, the slope of the spectral density of the temporal envelope of music has been shown to correlate well to its pleasing, dull, or chaotic character. In this paper, the temporal structure of a number of instantaneous psychoacoustic parameters of environmental sound is examined in order to investigate whether a 1/f temporal structure appears in various types of sound that are generally preferred by people in everyday life. The results show, to some extent, that different categories of environmental sounds have different temporal structure characteristics. Only a number of urban sounds considered and birdsong, generally, exhibit 1/f behavior on short to medium duration time scales, i.e., from 0.1 s to 10 s, in instantaneous loudness and sharpness, whereas a more chaotic variation is found in birdsong at longer time scales, i.e., of 10 s-200 s. The other sound categories considered exhibit random or monotonic variations in the different time scales. In general, this study shows that a 1/f temporal structure is not necessarily present in environmental sounds that are commonly perceived as pleasant

Experimental investigation of noise annoyance caused by high-speed trains

The observed difference in perceived annoyance caused by train and highway noise at the same averaged noise level, has led to the introduction of the ‘railway bonus’. This bonus has found its way to the noise legislation in many countries, leading to more relaxed restrictions on time averaged noise levels, LAeq. With the introduction of high-speed trains and train-like transportation systems based on magnetic levitation, the question has risen whether the railway bonus can still be applied. The design of the present experiment was different from previous efforts in many ways. Most importantly, it was conducted in a realistic setting, a holiday cottage, and participants were asked to engage in light daily activities during the tests. Traffic noise was reproduced in an ecologically valid way, using outdoor loudspeakers. A stepwise selection procedure was based on a screening questionnaire that was administered at the doorstep of 1500 people living around the test site, to be representative for the Dutch population. Finally, 100 representative participants were selected. The results from the annoyance experiment differed significantly from the results obtained using a much shorter listening test conducted afterwards. The LAeq-annoyance relationship obtained for the conventional high-speed train and for the magnetic levitation high-speed train did not differ significantly. The distance between the listening (recording) position and the track turned out to be the most important explanatory variable for the differences in exposure-response relationship observed, more so than vehicle speed or rise time.