Ljudet av vind i träd och dess inverkan på störning orsakad av trafikbuller
Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
The need to create a sustainable urban sound environment increases with the amount of unwanted noise and rising awareness of its negative consequences. In urban areas, it is mainly the sound of traffic that is considered unwanted; to attenuate these sounds have long been the only measure used extensively. Recently, alternative methods have been noted, such as masking that uses a similar but positively perceived sound that reduces the effect of the unwanted noise. Typical positive sounds that can meet the requirements for masking traffic noise are sounds from nature, like the sound of water. This sound is useful because of its similarities to traffic noise, and that its temporal character is continuous. Another sound from nature with similar characteristics is the sound of wind in the trees, this sound and its potential useful effect unlike water sounds are not thoroughly investigated. The purpose of this report is to investigate the ability of wind induced sound to mask the sound of traffic, and to find out if knowing that there are trees in the context of traffic noise affects the result. The methodology for this study has been a listening test in which the test participants listened to 21 sounds where the sound of trees and traffic where mixed. Half of the participants were assigned a short description of the visual environment they could expect during the test (a wooded city park), the remaining participants carried out the test without any environmental description. The tree sounds were recorded in quiet areas outside Lund, where the background sound were dominated by trees. The sounds of traffic were recorded in Malmö where the sound of traffic dominated the background sound. The final mixture of trees and traffic sounds were created in the editing process. 41 people participated in the listening test where each participant evaluated whether the sounds were perceived as unpleasant to pleasant on a scale from 1-100. The 21 sounds that were used during the test consisted of four different tree species: beech, oak, spruce, and a combination of birch and beech. The tree sounds were edited in the post process into two types of sounds for each tree; one type containing temporal variations in wind speed, and the second like a constant noise. Results and analysis show that audio stimuli containing both traffic and tree sounds generally were rated as more pleasant than the sound stimuli containing only traffic sound, despite the increased sound level. Sound stimuli containing no traffic sound were, however, judged as less pleasant with increased sound level. Subjects who received a description tended to judge sound containing traffic as less pleasant than those without description. This is likely linked to increased expectations of the sound environment from the participants who received a description. Tree Sound containing temporal variations was judged as more pleasant than the constant sounds overall, this effect was evident for the sound stimuli containing only tree sound, but did not occur for sound stimuli also containing traffic sound. The following conclusions can be drawn for the subjects who participated in the test; disturbance caused by traffic sound decreases when the sound of trees is present, regardless the type of tree sound and sound level. Knowing that trees are present increase disturbance from traffic sound due to raised expectations of acoustic environment. The results of this study show that trees have the potential to mask traffic noise, and could be applied as part of the planning of urban environment.
Place, publisher, year, edition, pages
2013. , 51 p.
Teknik, Akustik, ljuddesign, soundscape, ljudlandskap, ljudkvalité, psykoakustik, trafikbuller, informationsmaskering, landskapsarkitektur
IdentifiersURN: urn:nbn:se:ltu:diva-55185Local ID: c12c3cf9-ff27-423d-845e-3efb5f6a933aOAI: oai:DiVA.org:ltu-55185DiVA: diva2:1028566
Subject / course
Student thesis, at least 15 credits
Validerat; 20130320 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved