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Perspectives on wanted and unwanted sounds in outdoor environments: Studies of masking, stress recovery, and speech intelligibility
Stockholms universitet, Psykologiska institutionen.ORCID iD: 0000-0003-2059-0514
2013 (English)Doctoral thesis, comprehensive summary (Other academic)Text
Abstract [en]

An acoustic environment contains sounds from various sound sources, some generally perceived as wanted, others as unwanted. This thesis examines the effects of wanted and unwanted sounds in acoustic environments, with regard to masking, stress recovery, and speech intelligibility.

In urban settings, masking of unwanted sounds by sounds from water structures has been suggested as a way to improve the acoustic environment. However, Study I showed that the unwanted (road traffic) sound was better at masking the wanted (water) sound than vice versa, thus indicating that masking of unwanted sounds with sounds from water structures may prove difficult. Also, predictions by a partial loudness model of the auditory periphery overestimated the effect of masking, indicating that centrally located informational masking processes contribute to the effect. Some environments have also been shown to impair stress recovery; however studies using only auditory stimuli is lacking. Study II showed that a wanted (nature) sound improve stress recovery compared to unwanted (road traffic, ambient) sounds. This suggests that the acoustic environment influences stress recovery and that wanted sounds may facilitate stress recovery compared to unwanted sounds. An additional effect of unwanted sounds is impeded speech communication, commonly measured with speech intelligibility models. Study III showed that speech intelligibility starts to be negatively affected when the unwanted (aircraft sound) masker have equal or higher sound pressure level as the speech sound. Three models of speech intelligibility (speech intelligibility index, partial loudness and signal–to–noise ratio) predicted this effect well, with a slight disadvantage for the signal–to–noise ratio model. Together, Study I and III suggests that the partial loudness model is useful for determining effects of wanted and unwanted sounds in outdoor acoustic environments where variations in sound pressure level are large. But, in environments with large variations in other sound characteristics, models containing predictions of central processes would likely produce better results.

The thesis concludes that wanted and unwanted characteristics of sounds in acoustic environments affect masking, stress recovery, and speech intelligibility, and that auditory perception models can predict these effects.

Place, publisher, year, edition, pages
Stockholm: Department of Psychology, Stockholm University , 2013. , 55 p.
National Category
Psychology (excluding Applied Psychology)
Identifiers
URN: urn:nbn:se:sh:diva-29573ISBN: 978-91-7447-807-5OAI: oai:DiVA.org:sh-29573DiVA: diva2:905275
Public defence
2013-12-18, David Magnussonsalen (U31), Frescati Hagväg 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defence the following paper was unpublished and has a status as follows: Paper 3: Manuscript

Available from: 2016-02-26 Created: 2016-02-22 Last updated: 2016-09-19Bibliographically approved
List of papers
1. Auditory masking of wanted and unwanted sounds in a city park
Open this publication in new window or tab >>Auditory masking of wanted and unwanted sounds in a city park
2010 (English)In: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 58, no 5, 524-531 p.Article in journal (Refereed) Published
Abstract [en]

Auditory masking of unwanted sounds by wanted sounds has been suggested as a tool for outdoor acoustic design. Anecdotal evidence exists for successful applications, for instance the use of fountain sounds for masking road traffic noise in urban parks. However, basic research on auditory masking of environmental sounds is lacking. Therefore, we conducted two listening experiments, using binaural recordings from a city park in Stockholm exposed to traffic noise from a main road and sound from a large fountain located in the center of the park. In the first experiment, 17 listeners assessed the loudness of the road traffic noise and fountain sounds from recordings at various distances from the road, with or without the fountain turned on. In the second experiment, 16 listeners assessed the loudness of systematic combinations of a singular fountain sound and a singular road traffic noise. The results of the first experiment showed that the fountain sound reduced the loudness of road traffic noise close to the fountain, and that the fountain sound was equally loud or louder than the road traffic noise in a region 20-30 m around the fountain. This suggests that the fountain added to the quality of the city park soundscape by reducing the loudness of the (presumably unwanted) traffic noise. On the other hand, results from the second experiment showed that road traffic noise was harder to mask than fountain sound, and that the partial loudness of both sources was considerably less than expected from a model of energetic masking. This indicates that auditory processes, possibly related to target-masker confusion, may reduce the overall masking effect of environmental sounds.

National Category
Fluid Mechanics and Acoustics Psychology
Identifiers
urn:nbn:se:sh:diva-29576 (URN)10.3397/1.3484182 (DOI)000285049400007 ()
Note

 

Available from: 2011-01-14 Created: 2016-02-22 Last updated: 2016-09-19Bibliographically approved
2. Stress Recovery during Exposure to Nature Sound and Environmental Noise
Open this publication in new window or tab >>Stress Recovery during Exposure to Nature Sound and Environmental Noise
2010 (English)In: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 7, no 3, 1036-1046 p.Article in journal (Refereed) Published
Abstract [en]

Research suggests that visual impressions of natural compared with urban environments facilitate recovery after psychological stress. To test whether auditory stimulation has similar effects, 40 subjects were exposed to sounds from nature or noisy environments after a stressful mental arithmetic task. Skin conductance level (SCL) was used to index sympathetic activation, and high frequency heart rate variability (HF HRV) was used to index parasympathetic activation. Although HF HRV showed no effects, SCL recovery tended to be faster during natural sound than noisy environments. These results suggest that nature sounds facilitate recovery from sympathetic activation after a psychological stressor.

Place, publisher, year, edition, pages
Basel, Schweiz: MDPI Publishing, 2010
Keyword
soundscape, nature sounds, environmental noise, skin conductance level, heart rate variability, stress recovery
National Category
Psychology
Identifiers
urn:nbn:se:sh:diva-29575 (URN)10.3390/ijerph7031036 (DOI)
Funder
Swedish Research Council Formas
Note

This research was conducted in the research project Sustaining Acoustic Pleasantness within Rural and Community Development (SARCADE), funded by the Swedish Research Council FORMAS.

Available from: 2010-11-30 Created: 2016-02-22 Last updated: 2016-09-19Bibliographically approved
3. Aircraft noise and speech intelligibility in an outdoor living space
Open this publication in new window or tab >>Aircraft noise and speech intelligibility in an outdoor living space
2014 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 135, no 6, 3455-3462 p.Article in journal (Refereed) Published
Abstract [en]

Studies of effects on speech intelligibility from aircraft noise in outdoor places are currently lacking. To explore these effects, first-order ambisonic recordings of aircraft noise were reproduced outdoors in a pergola. The average background level was 47 dB L-Aeq. Lists of phonetically balanced words (L-ASmax,L- word = 54 dB) were reproduced simultaneously with aircraft passage noise (L-ASmax,L- noise = 72-84 dB). Twenty individually tested listeners wrote down each presented word while seated in the pergola. The main results were (i) aircraft noise negatively affects speech intelligibility at sound pressure levels that exceed those of the speech sound (signal-to-noise ratio, S/N < 0), and (ii) the simple A-weighted S/N ratio was nearly as good an indicator of speech intelligibility as were two more advanced models, the Speech Intelligibility Index and Glasberg and Moore's [J. Audio Eng. Soc. 53, 906-918 (2005)] partial loudness model. This suggests that any of these indicators is applicable for predicting effects of aircraft noise on speech intelligibility outdoors.

National Category
Psychology
Identifiers
urn:nbn:se:sh:diva-29574 (URN)10.1121/1.4874625 (DOI)000337110200049 ()
Note

Som manuskript i avhandling. As manuscript in dissertation.

Available from: 2014-07-25 Created: 2016-02-22 Last updated: 2016-09-19Bibliographically approved

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