Tham khảo tài liệu 'noise and vibration control episode 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | TM 5-805-4 AFJMAN 32-1090 Table 5-1. Molecular Absorption Coefficients dB per 1000 ft. as a Function of Temperature and Relative Humidity. Temperature Relative Hum id ity Octave Band Center Frequency Hzb 63 125 250 500 1000 2000 4000 8000 F C 14 10 10 50 90 32 0 10 50 90 50 10 10 50 90 59 15 10 30 50 Std Day 70 90 68 20 10 30 50 70 90 77 25 10 30 50 70 90 86 30 10 50 90 100 38 10 50 90 Taken from Standard Values of Atmospheric Absorption as a function of Temperature and Humidity SAE ARP 866A 15 March 1975 Society of Automotive Engineers Inc. 400 Commonwealth Drive Warrendale Penn. 15096. bUse 0 dB 1000 ft. for 31 Hz octave band. Used with permission from Society of Automotive Engineers Inc. upward into the sky and does not return to earth is bent down and returns to the earth sometimes passing above the attenuating ground surfaces and the vegetation thus yielding higher sound levels to the receiver. This can occur only for relatively large distances between source and receiver
