# Sound Environments in Large Public Buildings for Crowd Transit: A Systematic Review
## 3 Results
### Shopping Malls
An increase was observed when comparing the afternoon and evening with the early morning and midday time; similarly, sound levels for the weekends were higher than weekdays. \(T_{20}\) or \(T_{30}\) were separately measured in an unoccupied condition as 0.9 s in the food court and 1.4 s at the main entrance. The surveys used five-point Likert scales in the questionnaire with \"comfortable-uncomfortable\" as well as \"quiet-noisy\". \(L_{\text{Aeq}}\) were found to be correlated to acoustic comfort and loudness of staff working at these locations. [PERSON] et al. [40] investigated a large vestibule of the Shopping Centre Palace in Bratislava, Slovakia. The main volume of the space was 5750 m\({}^{3}\) and the total surface area of interior surfaces was 1850 m\({}^{2}\). It had a round shape with a diameter of 24 m with a dome-shaped partly transparent roof at a maximal height of 14.5 m. \(T_{30}\) and flutter echo were measured, and the former turned out to be 4.3 s at 1 kHz. The software simulation with different solutions based on user feedbacks approached the issue of background noise level, reverberation, and speech intelligibility. Large halls with parallel walls or circular shape with a distance between walls ca 9 m (e.g., 50 ms) will cause audible flutter echoes. No subjective surveys were detailed. [PERSON] and [PERSON] [41] studied six shopping malls, including [PERSON] (31,000 m\({}^{2}\)), [PERSON] (10,000 m\({}^{2}\)), [PERSON] (28,700 m\({}^{2}\)), [PERSON] (32,000 m\({}^{2}\)), [PERSON] (45,000 m\({}^{2}\)), and [PERSON] (30,000 m\({}^{2}\)) in China. \(L_{\text{Aeq-300 to500s}}\) were averaged between 9 a.m. and noon, between noon and 3 p.m., between 3 p.m. and 6 p.m. across seasons as 71.3, 73.3, 71.4, 70.8, 68.3, and 69.4 dB. The questionnaire using five-point Likert scales exploring loudness \"quiet-loud\" and acoustic comfort \"uncomfortable-comfortable\". The ratings for the former were 3.36, 3.52, 3.48, 3.32, 3.20, and 3.30, and those of the latter were 3.08, 2.73, 2.96, 2.80, 3.41, and 3.27. Results showed that loudness was influenced by visiting reason, visiting frequency, and length of stay. Acoustic comfort was affected by the above factors in addition to the season of visit. The ratings of users waiting for someone were lower in acoustic comfort, whereas users who went to the shopping malls more than once a month rated higher. The influences of the period of visit and accompanying person were found insignificant. [PERSON] and [PERSON] [42] selected an atrium (30,000 m\({}^{3}\)) as food court area of the CEPA shopping centre in Ankara, Turkey, exploring associations between measured noise levels and users' responses. \(L_{\text{Aeq-2 hr}}\) were obtained between 10 a.m. and noon, between noon and 2 p.m., between 4 p.m., and 6 p.m., between 8 p.m. and 10 p.m. during the weekdays and weekends. Results reveal that the average value in unoccupied condition was 44 dB, and those in occupied condition were 63.5 and 68.3 dB for weekdays and weekends. The peak occurred between noon and 2 p.m., between 6 and 8 p.m. during weekdays, and the highest value was delivered between 4 p.m. and 6 p.m. at weekends. Opening and closing of visiting time displayed as lowest of a day. The questionnaire used five-point Likert scales investigating noisiness with \"quiet-noisy\". The subjective ratingsof sound levels were demonstrated to correlate well with the measured ones, and noise level above 67 dBA led to a sudden increase in ratings. [PERSON] and [PERSON] [43] chose three atriums in Sheffield's Meadowhall, one of the largest shopping malls in the UK. \(L_{\text{Aeq-5 min}}\) were obtained with an interval of one hour for weekdays and weekends. Unsurprisingly the former was systematically lower than the latter. The values were around 65 to 80 dB, and reached 72.5 to 76.3 dB because of music, 70.0 to 78.7 dB, and 67.8 to 72.0 dB because of public address systems. The highest one was delivered as 82.6 dBA at 12:30 a.m. because of a show.