物理性污染控制习题答案噪声部分

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1.略2.略3.解：

??cf,c=340m/s,?1?340500?0.68m?2?5000340?0.068m?3?10000340?0.0034m4.解

L?20lgpe,'2ppppL?20lge?20lg0pp0pe?20lg20

?Lp?L'p?Lp?20lg2?6(dB)5.解

Q?I?SWSI?半=全=4?r2?2，SWS半2?r2DI=10lgQ?10lg2?3.01全6.解

Ln0.1Lpip?10lg(1n?10)?10lg1(108.5?108.7?108.6?108.4?108.9)?86.6(dB)i?150.1L10p??I?0.1L?0.1LI?p?2?p02?10pp?100.1(89?86.6)?1.74p20.1L10pp02DI?10lgQ?10lg1.74?2.47.解

1/9

I?p?e2?22?9.8?10?3(W/m2)0c1.2?340uue?A2??pA2???2pe??p20c2?0c?e0c??1.2?340??4.9?10?3m/s

W?IS?9.8?10?3?4??42?1.97(W)8.解

（1）按球面波考虑

Lp?LI?LW?20lgr?11LW?Lp?20lgr?11?88?20lg2?11?105(dB)

W?W0.1L0?10W?10?12?100.1?105?10?1.5?0.032(W)（2）Lp?LW?20lgr?11?105?20lg5?11?80(dB)9.解

p2A?p12?p22?52?22?41(Pa)pe?pA4122?4.5(Pa)p2D?e??4.52?1.46?10?4(W/m3)0c21.2?340210.解

Lp2?Lp1?20lgrr2??r1?2?r1??100?20lg10010?0.0062?100?10?=100-20lg10-0.0062?90=79.4(dB)11.解

707680.57880.1相减，约为80.380.4dB

65656812.解

6055相减60-1.6=58.4dB相加59dB

50dB

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13.解

Lp?10lg?10i?1n0.1Lpi?10lg(109.8?1010.1?1010.3?1010.2?109.9?109.2?108.0?106.0)?108.1(dB)

14.解

倍频程F=0.3

治理前响度指数分别为N1=18（sone），N2=50（sone），N3=55（sone），N4=50（sone），N5=30（sone）治理后

N1=10（sone），N2=23（sone），N3=29（sone），N4=23（sone），N5=22（sone）

治理前总响度N前=Nmax?F(?Ni?Nmax)=55+0.3?(18+50+55+50+30-55)=99.4(sone)治理后总响度N后=Nmax?F(?Ni?Nmax)=29+0.3?(10+23+29+23+22-29)=52.4(sone)

N-N响度下降百分率为?=前后?100%=99.4-52.4?100%?47%

N99.4前15.解

（1）Lp?10lg?10i?1n0.1Lpi?10lg(109?109.7?109.9?108.3?107.6?106.5?108.4?107.2)?101.6(dB)

（2）A计权后各中心频率声压值dB(A)分别为:

90-26.2=63.897-16.1=80.999-8.6=90.483-3.2=79.876-0=7665+1.2=66.284+1.0=8572-1.1=70.9

Lp?10lg?10i?1n0.1Lpi?10lg(106.38?108.09?109.04?107.98?107.6?106.62?108.5?107.09)?92.3dB(A)

16.解

货车72dB对应时间为2.5*45/60=1.875h客车68dB对应时间为1.5*20/60=0.5h其余时间为12-1.875-0.5=9.625h

0.1Lt??1nAii??10lg?11.875?100.1?7.2?0.5?100.1?6.8?9.625?100.1?60?L?10lg??10??eqT?12????i?1??10lg?11.875?107.2?0.5?106.8?9.625?106.0??65.5(dB)???12?

????3/9

17.解

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18.解f/Hz125250500100020004000Lp/dB576265676248响度指数1.963.85.57.46.63.4（sone）Nt=Nmax?F(?Ni?Nmax)?7.4+0.3??1.96+3.8+5.5+7.4+6.6+3.4+1.99-7.4?=14.38（sone）

LN?40?33.3lgN?40?33.3lg14.38?78.6(phon)

19.解

乙接受的等效声级为

LeqA?10lg??1?8?2?108.1?4?108.4?2?108.6?????84.1dB(A)

甲为82db(A)，所以乙的危害大。

20.解

LeqA?10lg??1?8?1?109.1?3?109?2?108.6?2?107.8?????88.1dB(A)

21.解

Ld?10lg??1?16?3?105.0?6?105.4?2?105.1?5?104.9?????51.9dB(A)Ln?10lg??1?8?2?104.9?2?104.6?4?104.4?????46.3dB(A)??L??dn?10lg??10.1Ld?8?100.1Ln?10?????24????16?10???????=10lg??116?105.19?24??8?105.63?????53.9?54dB(A)22.解]

(1).p??d2????24?B?4208?0.126

(2).fpp0?2c?hl?c??3400.126R2?hl?0.8d?2?0.1??4?0.8?8?/1000?596(Hz)23.解

8000361.995/9

n?S?ii25?10?0.02?25?10?0.25?2??25?10?10?5??0.04i?1(1).????81.5?0.096n850?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)

nni?1i?124.解

T60?0.161VS??0.161128?0.01?95?11.9(s)25.解

?nS?i?i?前?i?6?3+7?3??2?0.06+6?7?0.07+6?7?0.07?n1?S2??6?7+6?3+7?3??10.56162?0.065i?1i?nS?i?i?6?3+7?3??2?0.06+6?7?0.07+6前?i?1?7?0.8?n?S2??6?7+6?3+7?3??41.22162?0.254i?1iT60前?0.161VS??0.161?6?7?3?20.286=1.93(前2??6?7+6?3+7?3??0.065162?0.065s)

T60后?0.161VS??0.161?6?7?3?20.286=0.493(s后2??6?7+6?3+7?3??0.254162?0.254)??Lp?10lg后?=10lg0.254?5.9(dB)前0.06526.解

(1).砖

m??h?1.8?103?240?10?3?432(kg/m2)R?16lgm?8?16?lg432?8?50.2(dB)

f?0.551c2?E?0.551?3402cl0.24?1.8?103?71.9(Hz)2.45?1010(2).玻璃

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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?0.551cl233402.4?10?0.551???1784(Hz)E106?10?38.5?10

?27.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

??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?S1121R?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??S???吸声处理后房间常数为

R?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??'r2S???30.解

圆形：?r2?2000,r?25.24cm,P?2?r?158.5cm,P?158.5?0.08

S20007/9

正方形：a2?2000,a?44.72cm,P?4a,?178.9cm,PS?178.92000?0.089

1：5矩形：5b2?2000,b?20cm,P?2?6a?240cm,PS?2000240?0.12

2：3矩形：6b2?2000,b?18.3cm,P?(2a?3a)?183cm,PS?2000183?0.092

因此消声量以1：5矩形最大，以圆形最小，相差为L矩=???0?PSLL???0.12?1.5倍圆??0P'0.08'LS31.解

LR?20lgm?6?15,m?11.2,SS2?11.21?r22?r22?11.2,r2?11.2r2?11.2?1502?r21?2??6300012r12则r2?251(mm),R2?251?2?502(mm),

fmax??2n?1?C4l,125??2n?1?3404l,500l??2n?1??340,l?0.68?2n?1?N取值可为0，L为0.68m。复合上下限频率如下：

上限截止频率：fc340上=1.22D?1.22?0.502?555Hz

下限截止频率：fcS1340?r21下=2?Vl2?340??0.152??4Hz11.414?3.14?r2?l?l11.414?3.14??0.2512?0.68?332.解

(1).流通面积S??d2???0.12414?0.00785?m?2

LR?10lg?1?2K2??12,K?2.7

(2).V??CfKS?340?2.7?0.00785?0.036?m?3

r??63G???2?fr?2???V?2??632?0.036?0.049?m??c??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

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l??4V22?4?0.036?0.306(m)?d?d12?3.14??0.42?0.12?G?nS0,n?G?l?0.8d?l?0