# Differences Research on Human Overall Comfort Under Low Pressure
## 2 Method
### Experimental Research
#### 2.2.2 Experimental Design
The measurement instruments are shown in Figure 3a-c. The information about the equipment manufacturer is shown in Table 4. The measuring range of the thermal anemometer is 0.1-20 m/s. The instruments were calibrated prior to the experiment using a standard reference device. According to the literature [50], the objective parameters affecting human thermal comfort include the following: air temperature, relative humidity, average air velocity, and surface radiation temperature. Here, the operative temperature was used as the comprehensive index for evaluating thermal comfort [53]. Three temperature conditions were selected for winter and summer, respectively: 16 \({}^{\circ}\)C, 22 \({}^{\circ}\)C, and 24 \({}^{\circ}\)C for winter and 22 \({}^{\circ}\)C, 25 \({}^{\circ}\)C, and 28 \({}^{\circ}\)C for summer. For each pressure condition, the temperature level was maintained for 40 min. The first 15 min of each condition were an adaptation period, during which subjects filled in their personal information on the questionnaire. In the middle 20 min, the subjects filled out a thermal comfort questionnaire and scored it according to Table 1, while the experiment organizers recorded various parameters. The last 5 min were used for parameter adjustment. The experimental process is shown in Figure 4. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Equipment** & **Name** & **City** & **Country** \\ \hline Agilent34980A & Keysihgt Technoligies & Santa Rosa & America \\ \hline TJ-103 & Tianjin Hongda Instrument Factory & Tianjin & China \\ \hline KANOMAX 6004 & Kanomax Japan Inc. & Osaka & Japan \\ \hline SIMAA AS803 & Sima Instrument Group Co., Ltd. & Dongguan & China \\ \hline AWA6291 & Hangzhou Aihua Instrument Co., Ltd. & Hangzhou & China \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The information of the equipment manufacturer. Figure 3: Experimental instruments: (**a**) temperature data acquisition (Agilent34980A); (**b**) dry–wet bulb thermometer (TJ-103); (**c**) thermal anemometer (KANOMAX 6004); (**d**) illumination meter (SIMAA AS803); (**e**) sound level meter (AWA6291). (2) Luminous comfort experiment  
In relevant luminous regulations, the illuminance values are mostly used as the main parameter to measure the luminous environment [48; 49]. The illuminance was measured by a photometer as shown in Figure 3d, with a measurement range of 0 to 200,000 lx and an accuracy of \(\pm\)3%. By controlling the number of lamps that were switched on or off, the illuminance value was changed in the luminous experiment. The luminous experiment had three conditions, which were 120 lx (No. 5), 660 lx (No. 1, 3, 5, 7, 9), and 1200 lx (all lights on). Lamps with a 3200 K color temperature were installed on the top of the cabin. The layout is shown in Figure 2.  
Due to differences in human visual adaptation to light sources, the light adaptation time (the process of the eyes adapting from darkness to light) is relatively short, about 2-3 min [37]. The illuminance levels were gradually increased from dark to bright. Each pressure condition was maintained for 50 min. The experimental process is shown in Figure 5.  
(3) Acoustic comfort experiment  
The degree of noise interference to people was directly proportional to the noise intensity, increasing with higher sound pressure levels. In this study, the noise intensity served as an objective parameter for the acoustic comfort evaluation. Most countries around the world set the noise upper limit at 90 dB. Considering the measured noise in transportation cabins, a total of 6 conditions for sound intensity in the experiment were established. They were 60 dB, 65 dB, 70 dB, 75 dB, 80 dB, and 85 dB. The noise source was played through audio equipment. White noise was generated using Cool Edit Pro music editing and production software. According to research [54], rail transit and urban railways are the main sources of low-frequency noise.