n?S?ii25?10?0.02?25?10?0.25?2??25?10?10?5??0.04i?1(1). ????81.5?0.096 n850?25?10?25?5?10?5??2?Sii?1(2). A??Ai???iSi?25?10?0.02?25?10?0.25?2??25?5?10?5??0.04?81.5(m2)
i?1i?1nn24. 解
T?0.161V?0.161?95?11.9(s) 60128?0.01S?25. 解
n?S?ii?6?3+7?3??2?0.06+6?7?0.07+6?7?0.07i?1?前???10.56?0.065 n1622??6?7+6?3+7?3??Sii?1n?S?ii?6?3+7?3??2?0.06+6?7?0.07+6?7?0.8i?1?前???41.22?0.254 n1622??6?7+6?3+7?3??Sii?10.161?6?7?3T?0.161V??20.286=1.93(s)
60前2??6?7+6?3+7?3??0.065162?0.065S?前0.161?6?7?3T?0.161V??20.286=0.493(s) 60后2??6?7+6?3+7?3??0.254162?0.254S?后?L?10lg后=10lg0.254?5.9(dB) p0.065?前?26. 解
(1). 砖
m???h?1.8?103?240?10?3?432(kg/m2)R?16lgm?8?16?lg432?8?50.2(dB)2cf?0.551cl(2). 玻璃
233401.8?10?0.551???71.9(Hz)E0.24102.45?10?m???h?2.4?103?6?10?3?14.4(kg/m2)R?13.5lgm?14?13.5?lg14.4?14?29.6(dB)2cf?0.551cl27. 解
223S?S?S25123
1R?10lg1?10lg?35.4(dB)?4?2.87?1028. 解
方法一：墙和窗的隔声量分别为45dB和22dB，则它们的透射系数分别为10-4.5和10-2.2
233402.4?10?0.551???1784(Hz)?3E106?108.5?10???11?S??S??S?5?10?3?3?425?3?4?10?????2.87?10?43?10?4.5?3?10?2.2?144?1.6?10?3??1122?S?S1 121R?10lg1?10lg?28(dB)?3?1.6?10?S??S方法二：查图法
SR-R?45?22?23dB, 窗=1/3 墙窗S墙查表得：?R?17 则 R?45?17?2829. 解
2=100?0.02=2.04(m2)R?r21-?1-0.022
S??1NR?R?10lg??W??40?10lg1?20?30(dB)?4R?42.04r2??吸声处理后房间常数为
S???2=100?0.4=66.7(m2)1-0.41-?2
S??'1NR?R?10lg??W??40?10lg1?20?42.6(dB)'?4Rr2?466.7??30. 解
圆形：?r2?2000,r?25.24cm,P?2?r?158.5cm,P?158.5?0.08
S2000R?'r2S???正方形：a2?2000,a?44.72cm,P?4a,?178.9cm,P?178.9?0.089
S20001：5矩形：5b2?2000,b?20cm,P?2?6a?240cm,P?240?0.12
S20002：3矩形：6b2?2000,b?18.3cm,P?(2a?3a)?183cm,P?183?0.092
S2000因此消声量以1：5矩形最大，以圆形最小，相差为 L??PL矩=0S?0.12?1.5倍 L'0.08圆??PL0S'31. 解
SL?20lgm?6?15,m?11.2,2?11.2RS1 22?rr22?2?11.2,r2?11.2r2?11.2?150?63000212?r2r211??????则r2?251(mm),R2?251?2?502(mm),
??2n?1?C,125??2n?1?340,500l??2n?1??340,l?0.68?2n?1? max4l4lN取值可为0，L为0.68m。复合上下限频率如下：
c340上限截止频率：f上=1.22?1.22??555Hz
D0.502下限截止频率： fcf下=2?S1?r12340340??0.152???4Hz Vl11.414?3.14?r22?l?l11.414?3.14??0.2512?0.68?332. 解
(1). 流通面积S??d2???0.12?0.00785?m?2
414LR?10lg?1?2K2??12,K?2.7
(2). V?C?KS?340?2.7?0.00785?0.036?m?3
?f??63r?2?frG???c?2?22??63V??0.036?0.049?m? ???340???(3). 设计同轴圆筒形共振腔，其内径为100mm，外径为400mm，共振腔长为
l?4V4?0.036??0.306(m) ?d2?d23.14?0.42?0.1221????G?0,n?G?l?0.8d?,取L=2mm厚钢板，则开孔数为 l?0.8dS0nS0.049?2?10?3?0.8?0.5?10?2n???5?10?34(4). 验算
f?Cr2???2??15（孔）
G?3400.049?63.2Hz V2?0.036f?1.22c?1.22?340?1037Hz
上d0.4即所需消声范围内不会出现高频失效问题，共振频率波长为
??c?340?5.4m,?r/3?5.4/3?1.8m
rfr63所设计的共振腔消声器的最大几何尺寸小于共振波长的1/3，符合要求。