# An Experimental Study on the Influence of Soundscapes on People's Behaviour in an Open Public Space
## 2 Materials and Methods
### Signal Analysis  
During the experiment, a playlist of three music excerpts and a control condition (no music) was cyclically reproduced. Following the protocol of a previous experiment carried out by [PERSON] and colleagues [10], three instrumental pieces of music from contrasting genres (namely classical, jazz, and ambient electronic music) were used to ensure a high level of inclusiveness, involving different social groups in terms of age and gender [17]. It has been affirmed that conventional acoustic parameters for noise measurement--e.g., weighted sound pressure levels (SPLs)--are not sufficient for the adequate measurement of soundscape [18; 19; 20; 21; 22]. Since soundscape is a perceptual construct and music is known to trigger emotions and affect perception, soundscape and music are closely related; thus, the psychoacoustic parameters that have previously been applied mainly in music perception may also be applicable in soundscape research [23]. However, for the purpose of this study, it was decided to rely on pitch-related parameters for the selection of the stimuli to be used in the experiment. The pitch features are particularly significant in the field of environmental sounds and their perception [18]. Pitch maybe defined as \"that attribute of auditory sensation in terms of which sounds maybe ordered on a musical scale from high to low\", and is generally assigned by the frequency of a pure tone having the same subjective pitch as the considered sound [24; 25]. Another additional parameter defining other pitch sensations is the pitch strength (PA, a-dimensional), corresponding to the assessment of the sound along a scale from faint to distinct. It has been asserted that high pitch could be associated with feelings like strong activation, excitement, surprise, happiness. Low pitch instead could be associated with low activation, calmness, and quietness [26; 27; 28]. According to [PERSON] [21], the values of the most prominent pitches among environmental sounds are 4000 Hz for bird songs, 1000 Hz for fountain sounds, and no pitch perceived for river, sea waves, traffic, and wind. Western music generally refers to the 440 Hz pitch [29]. Therefore, the rationale for selecting the stimuli was having music excerpts with a relatively broad range of pitch features. These were selected amid those used in [PERSON]'s experiment in Brighton [10]: Classical (_Waltz of the Flowers_) Pitch 148 Hz, PA 9.3, Ambient (_Cirrus_) Pitch 577 Hz, PA 10.9, Jazz (_Creole Jazz_) Pitch 736 Hz, PA 5.3. The average background noise level in the observation area was found to be 60.7 dB, so the loudspeakers' gain was set accordingly, with the overall aim to exceed the background noise by at least 10 dB approximately in the whole observation area, as per the simulation in Section 2.2, so as to provide a reasonably homogeneous signal-to-noise ratio. Figure 3 shows the spectrum of the background noise level recorded on site, compared to the spectra of the three music excerpts, calibrated as if they had an overall sound pressure level of 75 dB. The spectra suggest that the music should be clearly audible over the background noise. Figure 3: One-third octave band spectrum of the background noise (BN) level (black line) averaged over the ten recording points reported in Figure 2, with minimum and maximum values (dashed lines), compared with the spectra of the three music excerpts (hypothetical broadband sound pressure level of 75 dB). The music excerpts (reproduced in loop) and the control were cycled repeatedly between 10:00 am and 1:00 pm (or between 11:00 a.m. and 2:00 p.m.) in one-hour slots. The experimental design consisted of 180 min of exposure for each of the four conditions (i.e., three music excerpts and the control), distributed during the five days of observation. A rotation of the stimuli was set across the week and the daily time slots, in order to obtain the widest range of observations for the same music excerpts in different days and times.