Bert De Coensel

Effects of natural sounds on the perception of road traffic noise

Recent studies show that introducing sound from water features in urban open spaces may reduce the loudness of road traffic noise, but it is not clear in which situations this measure also improves overall soundscape quality. This work describes a listening experiment on loudness, pleasantness, and eventfulness of stimuli that combine road traffic noise with fountain or bird sound at different sound levels. Adding fountain sound reduced the loudness of road traffic noise only if the latter had low temporal variability. Conversely, adding bird sound significantly enhanced soundscape pleasantness and eventfulness, more than what was achieved by adding fountain sound.

Speech recognition in noise with active and passive hearing protectors: A comparative study

The perceived negative influence of standard hearing protectors on communication is a common argument for not wearing them. Thus, augmented protectors have been developed to improve speech intelligibility. Nevertheless, their actual benefit remains a point of concern. In this paper, speech perception with active earplugs is compared to standard passive custom-made earplugs. The two types of active protectors included amplify the incoming sound with a fixed level or to a user selected fraction of the maximum safe level. For the latter type, minimal and maximal amplification are selected. To compare speech intelligibility, 20 different speech-in-noise fragments are presented to 60 normal-hearing subjects and speech recognition is scored. The background noise is selected from realistic industrial noise samples with different intensity, frequency, and temporal characteristics. Statistical analyses suggest that the protectors performance strongly depends on the noise condition. The active protectors with minimal amplification outclass the others for the most difficult and the easiest situations, but they also limit binaural listening. In other conditions, the passive protectors clearly surpass their active counterparts. Subsequently, test fragments are analyzed acoustically to clarify the results. This provides useful information for developing prototypes, but also indicates that tests with human subjects remain essential.

Modeling auditory attention focusing in multisource environments

In this paper, a mathematical submodel for auditory attention focusing is discussed in the framework of our ongoing research towards a unified model for soundscape perception. The submodel implements a balance between top‐down focusing, in which higher level cognition guides attention towards expected sources, and bottom‐up focusing, in which attention is triggered by the noticing of sound events. Attention elasticity ‐ the ability to switch attention between different environmental sounds ‐ depends on the current context (natural, urban...) as well as on the current activity of the modeled individual. The soundscape perception model is applied to case studies of simulated sound exposure in open area and in environments with a mixture of natural and man‐made sounds. A comparison of the simulation results with survey results shows that introducing a submodel for auditory attention focusing into our model for soundscape perception enhances its ability to predict the emergence of annoyance.

The rhythm of the urban soundscape

The influence of noise on the quality of the urban living environment has traditionally been studied focusing on negative effects on man, such as noise annoyance and sleep disturbance. Recently a more holistic approach, including positive and negative aspects as well as non-residential functions of the urban environment, has gained renewed interest. The label “urban soundscape” is often used to refer to this approach. Research towards selection and quantification of the acoustic descriptors of the urban soundscape is, however, still in an early stage. This paper draws on the analogy with music and self-organization to propose an indicator for studying the temporal structure of the urban soundscape. Applicability is illustrated by drawing a map of music-likeness of the soundscape in an urban area.

Characterizing the soundscape of tranquil urban spaces

Tranquil spaces provide restorative environments for urban residents and visitors and are therefore essential for health and quality of life. Tranquil spaces may be characterized through a combination of acoustical criteria, such as relatively low (percentile) sound levels and the relative absence of non-fitting sounds, and non-acoustical criteria, such as the presence of natural elements within the visual scene. Public urban parks and courtyards as well as private urban backyards are typically considered to be the most tranquil spots within a city. Current state-of-the-art in distributed measurement technology allows for long-term sound monitoring at these places. In this paper, the soundscape at a number of urban parks and backyards in the cities of Ghent and Antwerp is investigated through a detailed analysis of sound measurements performed over an extended period of time. An analysis of percentile sound levels, noise events and indicators for temporal and spectral structure is presented, and novel com...

1/f dynamics in the urban soundscape

Urban soundscapes are characterized by much more than loudness alone. Subjective description has been used by many researchers to grasp these additional dimensions, but very little objective criteria are found in literature. In this paper the dynamics of the soundscape is proposed as a potential indicator. By analyzing loudness and pitch fluctuations in longer sound fragments recorded in urban environment, 1/f spectral behavior at frequencies ranging from 0.01 to 10 Hz was discovered. Such behavior is typical for complex systems and was found to be very common in (classical) music, already in the seventies. Some hypotheses will be given on the origin of this frequency dependence of urban‐soundscape dynamics. The possibility of discriminating soundscapes on the basis of the frequency dependence of loudness and pitch fluctuation will be illustrated. For this purpose the urban soundscapes are compared to ‘‘extreme’’ soundscapes that have a very distinct character that is clear to every observer.

Acoustic summary as a tool for soundscape analysis and design.

The soundscape approach to designing sonic environments recognizes the importance of the sounds that can be heard by the attentive listener. These sounds not only contribute to the affective component of appraisal of the sonic environment but also carry the cultural identity of the neighborhood. For the purpose of discussion and communication in the soundscape design process, it is suggested to use a compilation of typical sounds amended with a sample of unusual sounds. To create such an acoustic summary automatically, a clustering system based on self‐organizing maps (also called Kohonen networks) using well‐chosen acoustical features is proposed. In addition, an oscillating neural network groups the sound into auditory streams with well defined duration. The proposed computational system continuously learns to identify the sounds that surround it and allows retrieving prototypical sounds for all identified clusters of sounds. Since the system is trained for a specific environment, the acoustic summary t...

Meaningless artificial sound and its application in urban soundscape research

Urban areas are increasingly being overwhelmed with uninteresting (traffic) noise. Designing a more matching soundscape for urban parks, quiet backyards, shopping areas, etc., clearly deserves more attention. Urban planners, being architects rather than musical composers, like to have a set of ‘‘objective’’ indicators of the urban soundscape at their disposal. In deriving such indicators, one can assume that the soundscape is appreciated as a conglomerate of sound events, recognized as originating from individual sources by people evaluating it. A more recent line of research assumes that the soundscape as a whole evokes particular emotions. In this research project we follow the latter, more holistic view. Given this choice, the challenge is to create a test setup where subjects are not tempted to react to a sound in a cognitive way, analyzing it to its individual components. Meaningless sound is therefore preferred. After selection of appealing sounds for a given context by subjects, objective indicator...