Effective soundscape characterisation of an acoustic metamaterial based window: A comparison between laboratory and online methods

Abstract

Qualitative investigation of the sound environment from human perception has lately reached wider attention through psychophysical and Soundscape descriptors; However, laboratory or in situ questionnaire can only reach a limited amount of demographic backgrounds, as, in a limited variety of cultural and geographical variation in a medium-short time, risking to bias/influence the results of the analysis. Starting from a related paper, the authors illustrated how to include human perception and psychoacoustics in evaluating an acoustic metawindow (AMW) unit effectiveness. This paper investigates the robustness of the mixed laboratory and online methodology and proves the validity of the exclusively online-based soundscape questionnaire method according to a number of headset setups. For this reason, a first Laboratory experiment with a fixed and controlled setup was followed by an Online 1 experiment, where the same participants took the same questionnaire (with a three weeks' time difference). Finally, the Online 2 experiment was used to broaden the sample background (results concerned the online method only). The setups mostly influenced the participants' responses by neutralising it (in 48% of the cases) while reporting a rate with an acceptable error (45% of Δrate = 0/5 and 39% of Δrate = 1/5). Wired headphones based rates agreed with the laboratory one consistently (36% of Δrate = 0 and overall CV = 2–25% through soundscape descriptors). Wired earphones had a similar Δrate percentage but with an overall more neutralised soundscape perception (overall CV = 1–40% compared with Laboratory rates). Wireless earphones caused the extremer Δrate (54% of Δrate = 3). Finally, natural and human noises are more detectable spontaneously, while traffic or other artificial noise are mostly recognised when directly addressed to the participants. This additional analysis gives more precise information about how efficient is the online method compared to the laboratory one. If accounted accordingly, an online-based soundscape questionnaire setup could also be viewed as a solid alternative to grasp a wider range of human perception points of view according to a broader cultural and geographical background.