Understanding soundscape in public spaces : a case study in Akköprü Metro Station, Ankara

In 2008, a working group of ISO/TC 43/SCI/WG 54 “Perceptual Assessment of Soundscape Quality of the International Organization for Standardization” was established and they published the first part of standardization “ISO 12913-1 Acoustics-Soundscape-Definition and conceptual framework” In their framework the acoustic environment divides into two main categories according to places; indoor and outdoor acoustic environment. The working group ISO/TC 43/SCI/WG 54 is being to standardize the methods and parameters of soundscape quality outdoors and point out both the negative and positive aspects of sounds environment as perceived by people. Besides the soundscape quality outdoors, indoors are also needed to be studying in the field. This study has been designed to understand the indoor acoustic environment of the metro station which is chosen as a public space. Aim of this study is to find out both negative and positive aspects of indoor acoustic environment as perceived by users in metro station. In order to compare outdoor and indoor soundscape qualities, Akköprü Metro Station and its immediate surrounding were chosen as a case study in Ankara, Turkey. The park shared the same environment with metro station was chosen as an outdoor environment/open public space. Entrance of the metro station was chosen as a semi open public space and the platform of the metro station was chosen as an indoor environment/enclosed public space. Within “a degree of enclosure” context, objective, subjective and psychoacoustics parameters for soundscape quality were measured in three spaces. As objective parameters, A-Weighted Equivalent Continuous Sound Levels (LeqA), Sound Pressure Levels" (SPL), Reverberation Time (RT), Speech Transmission Index (STI) were measured. For subjective parameters, sound recordings were taken with soundwalk method and noise annoyance surveys were applied simultaneously. A listening test and a survey were prepared to understand if spaces could be recognized/understood just by hearing. For psychoacoustics parameters, questionnaires were prepared and subjects were asked to fill in personal information and for each sound recording they listen, they were asked to fill in four open ended questions and choose from seventeen adjective pairs prepared with one to five likert scale. Ninety applicants participated in a listening test. Results showed that, acoustical measurements were higher than the permissible limits given in regulations. According to the noise annoyance survey results, enclosed spaces have the highest noise annoyance rating. Demographic factors such as age, gender, education level and space recognition did not showed any significant correlation. According to the listening test results, 70% of the subjects were able to determine spaces correctly as open, semi open or enclosed. Only 55% of the subjects were able to recognize the spaces. Soundmarks of the spaces show similarities. In open spaces subjects tended to choose adjectives such as "pleasant", "calming", "natural", "joyful"; while in enclosed spaces they tended to choose adjectives such as "unpleasant", "stressing", "artificial" , "empty".