環(huán)境影響評價11噪聲-展示頁
2025-05-25 22:40本頁面
【正文】 使聲壓級相同，人耳聽到的響亮程度很可能不同。頻率高，音調高，頻率底則音調低。聲波中兩個相鄰壓縮區(qū)或膨脹區(qū)之間距離稱為波長。每秒鐘密 疏變化一次稱 1赫（ Hz）。 環(huán)境噪聲源的分類 ? 工廠噪聲 鼓風機、氣輪機、織布機、沖床 ? 建筑施工噪聲 打樁機、混凝土攪拌機、卷揚機和推土機 ? 交通噪聲 汽車、火車、船舶汽笛和飛機 ? 社會生活噪聲 人群大聲喧鬧、高音喇叭和收放機等發(fā)出的過強的聲音 聲音的頻率、波長和聲速 ? Sound is produced by vibrating objects and reaches the listener39。環(huán)境影響評價 第七章 噪聲環(huán)境影響評價 ? 噪聲和噪聲評價量 ? ? What are sound and noise? Sound is what we hear. Noise is unwanted sound. The difference between sound and noise depends upon the listener and the circumstances. Rock music can be pleasurable sound to one person and an annoying noise to another. In either case, it can be hazardous to a person39。s hearing if the sound is loud and if he or she is exposed long and often enough. 噪聲指人們不需要的頻率在 20~20210 Hz范圍內的可聽聲。s ears as waves in the air or other media. When an object vibrates, it causes slight changes in air pressure. These air pressure changes travel as waves through the air and produce sound. ? 單位時間內空氣分子發(fā)生的密 疏變化的周期稱頻率。人耳所能覺察的頻率在 20~20210Hz間。 ? c =λf ； f= 1 / T ； c =λ/ T ? c≈ + t Generation of Sound Waves Table 1 Approximate Speed of Sound in Common Materials Medium Sound Velocity (ft/s) m/s Air, dry (0C and mm Hg) 1,100 330 Wood (soft along the fibre) 11,100 3400 Water (15C) 4,700 1400 Concrete 10,200 3100 Steel 16,000 5000 Lead 3,700 1200 Glass 18,500 5500 Hydrogen (0C and m) 4,100 噪聲的基本評價量 ? What is a decibel 是指兩個相同的物理量（例如 A1和 A0 ）之比取以 10為底的對數并乘以 10（或 20），即 N=10 log (A1/ A0) dB where the log is to base 10 If the second produces twice as much power than the first, the difference in dB is 10 log (P2/P1) = 10 log 2 = 3 dB. If the second had 10 times the power of the first, the difference in dB would be 10 log (P2/P1)= 10 log 10 = 10 dB. If the second had a million times the power of the first, the difference in dB would be 10 log (P2/P1) = 10 log 1000000 = 60 dB. Plot of 10 log (P2/P1) 聲壓和聲壓級 ? What is
環(huán)評公示相關推薦
鄂ICP備17016276號-1