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习题练习:gc textbook chapter 12 Sound



 作者: admin发布日期: 2025-02-02 21:19   总分: 110分  得分: _____________

答题人: 匿名未登录  开始时间: 25年01月19日 20:51  切换到: 整卷模式

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1#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
What is the evidence that sound t.thm d;ha8q 3m )fw(llravels as a wave?
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2#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
What is the evidence that sound ly12jhakj +*i is a form of energy?
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3#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Children sometimes play with a homemade “telephone” by attachmfiwams.;i + 7ing a string to the bottoms of two paper cups. When the string is stretched and a child speaks into one cup, the sound can be heard at the other cup (Fig. 12–29). Explain clearly how tha7 s;mm+wii. fe sound wave travels from one cup to the other.
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4#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
When a sound wave passes from air into water, do you expect the frequency or bg uft,2jm*k9 wavelengt,bkfg*t29m j uh to change?
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5#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
What evidence can you give that the speed of sou n7 pbo-3mfas8nd in air does not depend significanf3 8 amb-n7psotly on frequency?
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6#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
The voice of a person who has inhaled helium ;k.p2,zth(c axse+ desounds very high-pitched. Why?
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7#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
How will the air temperature in a room affect thcob+p qqs4 j,.e pitch of organ pipes?
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8#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Explain how a tube might be used as a filter to reduce the amp,(lwy+rac f /t /z1oeklitude of sounds in various frek o,awy+(c / eft1lrz/quency ranges. (An example is a car muffler.)
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9#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Why are the frets on a guitto8q lwodl- +dg.-z .lar (Fig. 12–30) spaced closer together as you move up the fingegzd8t w--..old olql+rboard toward the bridge?

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10#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A noisy truck approaches you from behj7e,s h 2l;riodg9gg)ind a building. Initially you hear it but cannot see it. When it emerges and you do see it, its sound is suddenly “brighter” — you hear more of the high-frequency noise. Expdg)ig;2 sohr lg7 e9j,lain. [Hint: See Section 11–15 on diffraction.]
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11#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Standing waves can be said to be du 6,xat4z2oue ye to “interference in space,” whereas beats can be said to be due to “int4t ezu,axy 2o6erference in time.” Explain.
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12#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
In Fig. 12–16, if the frequency of the sp:loicn -n i+z2q 8ikx3eakers were lowered, would the points D and C (where destructive and constructive interference occur) mn-ni : +x q3lok8czii2ove farther apart or closer together?
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13#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Traditional methods of protecting the hearing of people who work in areas 60a4mnxvb; bmq*. 9wr ei4linwith very high noise levels have consisted mainly of efforts to block or reduce noise levels. With a relatively new technology, headphones are worn that do not block the ambie 0i;nnbeixmq 9 wv .4*al64brmnt noise. Instead, a device is used which detects the noise, inverts it electronically, then feeds it to the headphones in addition to the ambient noise. How could adding more noise reduce the sound levels reaching the ears?
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14#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Consider the two waves shown in Fig. 12–31. g 0pqavjf dvs7i(82t 1w:q,xp(hqvt 3 Each wave can be thought of as a superposition of two sound waves with slightly different frequencies, as in Fig. 12–18. In which of the waves, (a) or (b), are the 8qg tv2:p0qhjwx3sdv 7fp a(v1,ti(qtwo component frequencies farther apart? Explain.
(12-31)
(12-18)
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15#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Is there a Doppler shift if the source,r p)t kc;bq2mg, ggnej) 4b+n and observer move in the same direction, with the same velocity? Explain)r+ tp,be,q g4n mg)nbcg2j;k.
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16#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
If a wind is blowing, will thi 3t76wyqisdh 6+vytig(b+:tjs alter the frequency of the sound heard by a person at rest with respect to the source? Is the wavelength or velocity ch gwsit b37q:6 t6v+t y(jhd+iyanged?
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17#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Figure 12–32 shows various positions of a dw75z2km7ud rovwrqe 4-l 18ochild in motion on a swing. A monitor is blowing a whistle in front of the child on the ground. At which position, A through E, wo m2ue45v8rl-7 d d1wrwzo 7qkill the child hear the highest frequency for the sound of the whistle? Explain your reasoning.

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18#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A hiker determines the lengthg2(i jhgedtmx3s6) r * of a lake by listening for the echo of her shout reflected by a cliff at the far end )h g d36segi jx2rt(m*of the lake. She hears the echo 2.0 s after shouting. Estimate the length of the lake.    ×102m

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19#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A sailor strikes the side of his ship just below the waterline. He hears the ecw,hrytq h(2mj 4dk/p5ho of the sound reflected from the ocean floor directly below 2.5 s later. How deep is the oymqh 2w/j(hpr4k,dt 5cean at this point? Assume the speed of sound in seawater is 1560 m/s (Table 12–1) and does not vary significantly with depth.    ×103m

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20#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Calculate the wavelengtwi0l .bch9lh1 .gv5n nhs in air at 20 C for sounds in the maximum range of human hearing, 20 Hz to 20,000 Hz. λ20Hz =    m λ20kHz =    ×102 m(b) What is the wavelength of a 10-MHz ultrasonic wave?    ×105m

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21#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An ocean fishing boat is drifting just above a schoo: d. l *qj(n9)xabeo.nte 0cgxl of tuna on a foggy day. Without warning, an engine backfire occurs on onxcjb 9:e)xdg q0..tl*a(en another boat 1.0 km away (Fig. 12–33). How much time elapses before the backfire is heard (a) by the fish,    s (b) by the fishermen?    s


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22#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A stone is dropped from the top of a cliff. The splash it makes when stru h/de8+*kvgriking the water below is heard 3.kv/g due8*+ hr5 s later. How high is the cliff?    m

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23#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A person, with his ear to tpu l1 tu1gj3x emy1 +24eg4m7x -qmaklhe ground, sees a huge stone strike the concrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other in the concrete, and they are 1.k 3pe11uxm1 gqlmux42a4yjg- m+7te l 1 s apart. How far away did the impact occur? See Table 12–1.    ×102m

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24#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Calculate the percent error made over onaprz d ) a7m;gsqjlsv+(e+ 1+be mile of distance by the “5-second rule” for estimating the distance from a lightning strike if the temperature is sabpsdamr1 )(+vl ez++jq;g 7 (a) 30 C,    % (b) 10 C    %.

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25#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the intensity of a sound at the pain level of 120 dB? s:44zytcz shh(h-v q3    W/m2Compare it to that of a whisper at 20 dB.    ×1010W/m2

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26#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the sound level of a sound whose myewc/bewg1 ;4 r0gmi ssk514u sg*(b intensity is 2×106W/m2?    dB

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27#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If two firecrackers produce a sound level of 95 s3s 3ed,r0rxjdB when fired simultaneously at a certain place, what will be the sound level if only one is exploded? [Hint: ss33r,rd exj 0Add intensities, not dB’s.]    dB

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28#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A person standing a certain distancev6:umj, +j8pn-lz kgo+5pv yg from an airplane with four equally noisy jet engines is experiencing a sound lj5o8 gg+nkmu - lvjpyv6 :p+z,evel bordering on pain, 120 dB. What sound level would this person experience if the captain shut down all but one engine? [Hint: Add intensities, not dB’s.]    dB

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29#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A cassette player is said to have a signal-to-noise ratigax(l7p 2djg x -ga7*no of 58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensities of the signal and the background noise for each d axp(gggjd n 2*77-xalevice? 58 dB =    ×105 dB =    ×109

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30#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Estimate the power output of sound from a per9eql* k5b;vqkib m5 c1son speaking in normal conversation. Use Table 12–2.b bkq 5ml9evc*i5kq1 ; Assume the sound spreads roughly uniformly over a sphere centered on the mouth.    ×106W(Round to the nearest integer)
(b) How many people would it take to produce a total sound output of 100 W of ordinary conversation? [Hint: Add intensities, not dB’s.]    ×107people

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31#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 50-dB sound wave strikes anzq*ok ga*7:rs:v) h ef eardrum whose area is 5×105m2 (a) How much energy is absorbed by the eardrum per second?    ×1012W (b) At this rate, how long would it take your eardrum to receive a total energy of 1.0 J?   ×103yr

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32#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Expensive amplifier A is rated at 250 W, while the more moez klr,:1n sc5dest amplifier B is rated at 40 W. (a) Estimate the sound level in decibels yol,n1sec 5:rkz u would expect at a point 3.5 m from a loudspeaker connected in turn to each amp.I250 =    dB I40 =    dB (b) Will the expensive amp sound twice as loud as the cheaper one?

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33#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  At a rock concert, a dB meter registered 130 dB when placed 2.8 m in fron rp*oq)0 05tvconpj k8t of a loudspeaker ptc0n 5qvpo08k *oj)r on the stage.
(a) What was the power output of the speaker, assuming uniform spherical spreading of the sound and neglecting absorption in the air?    ×102W(“Round to one decimal place)
(b) How far away would the sound level be a somewhat reasonable 90 dB?   ×102m

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34#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Human beings can typically dete+-k1eouizkq a+f3 uv-ct a difference in sound level of 2.0 dB. What is the ratio of the amplitudes of two sounds whose lev q zki3+o-fk1v+u-euaels differ by this amount? [Hint: See Section 11–9.]   

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35#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If the amplitude of a sound wave is tripled, (a) by what factor will-jogxtb 12/a*q dw3kahj,k g3 the intensity indgbaoxw3k,-qg htjak/ 2 3 1j*crease? Increase by a factor of    (b) By how many dB will the sound level increase?    dB

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36#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two sound waves have equal displacement amplitudes, butdvlo: g/4xjb g q7kw,9 one has twice the frequency of the other. What is the ovl7g bw/ kj 9gq4dx,:ratio of their intensities?   

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37#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What would be the sound leve * ij1*txlkhq0l (in dB) of a sound wave in air that corresponds to a ditxj q** lk1h0isplacement amplitude of vibrating air molecules of 0.13 mm at 300 Hz?    dB

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38#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 6000-Hz tone must have jf(zbqp(ox ze5; s7wp6adc 8 1what sound level to seem as loud as a 100-Hz tone that has a 50-dB sound level? (See cs5oqjdbz;a68ef1x z ( wpp(7 Fig. 12–6.)    dB


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39#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
What are the lowest and highest frequencies that an ear can detect whqud6t2 6 xi1zqen the sound level1 2x66zqqit du is 30 dB? (See Fig. 12–6.)

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40#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Your auditory system can accommodate a huge range of sound levelsovf,0k/ v l/bn r5oe(x. What is the ratix( vl/v,/0brokf5en oo of highest to lowest intensity at
(a) 100 Hz,×10a a =   
(b) 5000 Hz? ×10a a =   
(See Fig. 12–6.)



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41#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The A string on a violin has a fundamental frequency of 440 H ,w6(ci6rgcg az. The length of the vibrating portion is 32 cm, and it has a mass of 0.35 g. Under what tension must the string begcwg6a c ,6r(i placed?    N

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42#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An organ pipe is 112 cm long. What are the fundamental and first three audil74 dwmwc6 y-l9j.l4g jab .uoble overtu olm49 jab46g7dcl-yl wj..wones if the pipe is
(a) closed at one end, f1 =    Hz f3 =    Hz f5 =    Hz f7 =    Hz
(b) open at both ends?f1 =    Hz f2 =    Hz f3 =    Hz f4 =    Hz

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43#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) What resonant fre+9lom dbpm:snx7k- f w7tld:7quency would you expect from blowing across the top of an empty soda bottle that is 18 cm7xmdlow9:+mnd -p 7l7s: fbkt deep, if you assumed it was a closed tube?    Hz (b) How would that change if it was one-third full of soda?   Hz

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44#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If you were to build a pipe organ with open-tube pipes spanning the ;vn-j ky-(p ourange of human hearing (20 Hz to 20 kHz), what would be the range of the lengths of pipes opv uj;n-(yk -required? L20Hz =    m L20kHz =    ×103m

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45#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A tight guitar string has a frequency of 540 Hz as its third har.a(i6 zaxfifvz)(s1q; x t4tn monic. What will be its fundamental frequency if it is fingervza ai1xtq4) f.(t6;z ifs(xned at a length of only 60% of its original length?   Hz

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46#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An unfingered guitar string is 0.7vwq0eq e 6/ 0usw1sql2r1d .xp3 m long and is tuned to play E above middle C (330 xs eqlv0wq1dsp 20. q1re/w6u Hz).
(a) How far from the end of this string must the finger be placed to play A above middle C (440 Hz)?    m
(b) What is the wavelength on the string of this 440-Hz wave?    m
(c) What are the frequency and wavelength of the sound wave produced in air at 20°C by this fingered string?    Hz    m

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47#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Determine the length of an open organ pipe thatc-hx3(.d jnbr emits middle C (262 Hz) when the t-nbr (jdx hc.3emperature is 21 C.    m
(b) What are the wavelength and frequency of the fundamental standing wave in the tube?    Hz    m
(c) What are λ and fin the traveling sound wave produced in the outside air?    Hz    m

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48#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An organ is in tune at 20 gnd. /uth4 sf9 C. By what percent will the frequency be off at 5.0 C?    %

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49#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How far from the mouthpiece of the fluk/9 x2sdxzzgeam ( z4t(l-awv dw142rte in Example 12–10 should the hole be that must be uncovered to play D above middle C at2kz1mz4glaad wv-de r(z24x w/txs ( 9 294 Hz?    m

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50#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) At T = 20 C how long must an open organ pipe be to have a fundamental frequency of 294 Hz?    m
(b) If this pipe is filled with helium, what is its fundamental frequency?   Hz

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51#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A particular organ pipe can resonate at -ag c,ul 4.hur264 Hz, 440 Hz, and 616 Hz, but not at any otl4 chuua ,-gr.her frequencies in between. (a) Show why this is an open or a closed pipe.   (b) What is the fundamental frequency of this pipe?   Hz

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52#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A uniform narrow tube 1.80 m long is open at both ends. It resonates at two su s.v)spemtm*2 ccessive harmonics of frequencies 275 Hz and 330 Hz. What spv.em2m s*)tis
(a) the fundamental frequency,    Hz
(b) the speed of sound in the gas in the tube?    ×102 m/s

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53#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A pipe in air at 20 hu24*yqi wfbj; 3lxw bs9 1;wk C is to be designed to produce two successive harmonics at 240 Hz and 280 Hz. How long must the pipe be, and is it open or closed?    f =    m

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54#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How many overtones are present within the audible range for a 2.14-m-longq/0x 2)xcwr,o u yzl04bvpe/m organ piomvxzcu4wb/0l,0r 2/y ) pqxepe at 20 C
(a) if it is open,   
(b) if it is closed?   

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55#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The human ear canal is approximately 2.5 cm long. It is open to the outsid0 ,/ km h7gfpxw3)wnuoe and is closed at the other end by the eardrum. Estimate the frequencies (in the audible range) of the sfn w k,037wuog/p)h xmtanding waves in the ear canal. What is the relationship of your answer to the information in the graph of Fig. 12–6? f1 =    Hz f3 =    Hz f5 =    Hz


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56#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A piano tuner hears one beat ever1vvoxp9 d.vss0, ;u lky 2.0 s when trying to adjust two strings, one of which is sounding 440 Hz. How far off in frequency i vsk d;o v0l.,us9vx1ps the other string? ±    Hz

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57#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the beat frequency if middle C (t0 :z;fz+mq omaxhb4-262 Hz) and C (277 Hz) are played together?    Hz What if each is played two octaves lower (each frequency reduced by a factor of 4)?    Hz

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58#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A certain dog whistle operates at 23.5 kHz, while another (brand X) operan ga2;tqnq w5r9t:*u4 xcz f.ztes at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whine of frequency 5000 Hz occurs when they are pla:t9* ;nr tqqnw4zufcxz .25gayed simultaneously, estimate the operating frequency of brand X.    kHz

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59#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A guitar string produces 4 beats/s when sounded with a 350-Hz tuning fork andi-cmuyu4ef32 9 beats/s when sounded with a 355-Hz tuning fork. What is the vibrational freq43 uy2efiucm- uency of the string? Explain your reasoning.    Hz

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60#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two violin strings are tuned to the same frequency, 294 Hz. Thdue th/(a6z(qk1ssza0 n2fa ()2 enu;zgjpr-e tension in one string is then decreased by 2.0%. What will be the beat frequency hefhs 2nzrja/2d (z-6g)puea0e(; tk1s nu( za qard when the two strings are played together? [Hint: Recall Eq. 11–13.]    Hz

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61#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How many beats will be heard if two identical fl)swc2th fk3n vo; :byn7, nhi6utes each try to play middle C (262 Hz);3v7ykti6 scbo, h f) nwh:n2n, but one is at 5.0°C and the other at 25.0 C?    beats/sec

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62#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You have three tuning forks, A, B, and C. Fork B has a frequency of 441 Hz; tkqy,l t)*dg+w.p iw; when A and B are sounded together, a beat frequency of 3 Hz is heard. When B and C are soytqg )dk+. ;twilp,w*unded together, the beat frequency is 4 Hz. What are the possible frequencies of A and C? What beat frequencies are possible when A and C are sounded together?fA =    Hz or    Hz
fC =    Hz or    Hz
|fA-fC|    Hz or    Hz

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63#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two loudspeakers are 1.80 m apart. A person stands 3.00 m from one speaker anguuei946 zk/ti +y6yuda1sw-i )tfn1d 3.50 m from the other6w/tiy-afnu d9 1s+uu t1i )4ge z6yik.
(a) What is the lowest frequency at which destructive interference will occur at this point? f =    Hz
(b) Calculate two other frequencies that also result in destructive interference at this point (give the next two highest). Let T = 20 C    Hz    Hz

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64#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two piano strings are supposed to be vibrating at 132 / par6og n29lx :gafo*bat( *uHz, but a piano tuner hears three beats every 2.0 s when they are played together. (a) If one is vibrating at 132 Hz, what must be the frequency og ra( 6fa/p b *a2*ot9gxno:luf the other ?   Hz    Hz
(b) By how much (in percent) must the tension be increased or decreased to bring them in tune?   % increase    %decrease

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65#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A source emits sound of wavelengths 2.64 m and 2.76 r2. c28sxb 5kdbf6 h30 lkc8*2jwagwj u5n wdlm in air. How many beats per second will be he 85c*ku dfd20gnbakwrjxhcl2 8ws26lb35.jw ard? (Assume T = 20 C)    Hz(round to one decimal place)

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66#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The predominant frequency o, cs)-h-u yoszf a certain fire engine’s siren is 1550 Hz when at rest. What frequency d),ysuz-o chs -o you detect if you move with a speed of 30 m/s
(a) toward the fire engine,    Hz
(b) away from it?   Hz

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67#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You are standing still. What frequency w8wbdm/ r,y 5rdo you detect if a fire engine whose siren emits at 1550 Hzr8w/5mw ,b rdy moves at a speed of 32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

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68#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Compare the shift in frequency if a 2000-Hz source is moving toward 03x86cbvqv wk.cpw1 m you at 15 m/s versus you moving toward it at 15 m/s Are the b0 c1x w8. qvvkc3pwm6two frequencies exactly the same? Are they close? fsourcemovine    Hz
fobservemovine    Hz
(b) Repeat the calculation for 150 m/s and then again
fsourcemovine    ×103Hz
fobservermovine    ×103Hz
(c) for 300 m/s What can you conclude about the asymmetry of the Doppler formulas?fsourcemovine    ×103Hz
fobservermovine    ×103Hz

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69#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two automobiles are equipped with the samkb /82xmkre4q e single frequency horn. When one is at rest and the other is moving toward the first at 15 m/s the driver at r br4x/k2e8kmq est hears a beat frequency of 5.5 Hz. What is the frequency the horns emit? Assume T = 20 C    Hz

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70#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bat at rest sends out ultrasonic sound wr0q12 wy urpd:6xdqs.aves at 50.0 kHz and receives them returned from an object moving directly away from it at 25 m/s What is the reyqp2d1 sq.6uwr: r0dxceived sound frequency?    ×104 Hz

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71#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bat flies toward a -jc) hhj84r a zyt,6erbs (8wewall at a speed of 5 m/s As it flies, the bat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency does the bat h8we)z cr-btry4 sjej h,a86h (ear in the reflected wave?    ×104 Hz

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72#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  In one of the original Doppler7znl h.85 qiex experiments, a tuba was played on a moving flat train car at a frequency of 75 Hz, and a second identical tuba played the same tone wh7lzi xe .5nq8hile at rest in the railway station. What beat frequency was heard if the train car approached the station at a speed of 10 m/s ?   Hz

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73#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A Doppler flow meter uses ultrasound waves bs 99eide89m ugxn( f2to measure blood-flow speeds. Suppose the device emits sound at 3.5 MHz, and the speed of sound in hsd9iu9x(ee 9n2fm8 gbuman tissue is taken to be 1540 m/s What is the expected beat frequency if blood is flowing in large leg arteries at 2 cm/s directly away from the sound source?   Hz

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74#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The Doppler effect using ultrasonic waves of frequenc qo(x-j 09ax2eem im6my 2.25×106Hz is used to monitor the heartbeat of a fetus. A (maximum) beat frequency of 500 Hz is observed. Assuming that the speed of sound in tissue is 1.54×103 m/s calculate the maximum velocity of the surface of the beating heart.    m/s

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75#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A factory whistle emits sound of frequency 570 Hz. Whsz1ogth2pw ka7gh1; ; (9m ww1ov:wpoen the wind velocity is 12 m/s pwwgh1zovk 1 p;9;:swm(o2 awt g h1o7from the north, what frequency will observers hear who are located, at rest,
(a) due north,   Hz
(b) due south,   Hz
(c) due east,    Hz
(d) due west, of the whistle? What frequency is heard by a cyclist heading    Hz
(e) north    Hz
(f) west, toward the whistle at 15 m/s?   Hz
Assume T = 20 C

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76#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How fast is an object movingw ofz7+u+/b ui on land if its speed at 20 C is Mach 0.33?    m/s
(b) A high-flying jet cruising at 3000 km/h displays a Mach number of 3.2 on a screen. What is the speed of sound at that altitude?    m/s

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77#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An airplane travels at Mach 2.3 where the s) h 2pssej4/gzpeed of sound is 310 m/s (a) What is the angle the shock wave makes with the direction of the airplane’s mot)2j/ ehz gs4psion?   
(b) If the plane is flying at a height of 7100 m, how long after it is directly overhead will a person on the ground hear the shock wave?    s (Round to the nearest integer)

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78#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A space probe enters the thin atmosphere of a plana6wq y 4ox *)azi7p/ddet where the speed of sound is only abz*x7do6 i4a/)wyd pa qout 35 m/s
(a) What is the probe’s Mach number if its initial speed is 15000 km/h    (Round to the nearest integer)
(b) What is the angle of the shock wave relative to the direction of motion?   

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79#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A meteorite traveling 8500 m/s strikes the ocean. Determine the shock waz1ii4 ij7dc*p7g wann (1u,p.e l j8teve angle it8j.*7gl(penw4d1,z1n aeu ci j i7pit produces
(a) in the air just before entering the ocean,    (Round to the nearest integer)
(b) in the water just after entering.   
Assume T = 20 C

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80#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Show that the angle ot; ok mf1-(qo8vea1f/theta a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.
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81#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You look directly overhead and see a plane exactly 7rd3 x myrtbjybiy1/ (3 .5eqoa9 pwfegn5(9w1.5 km above the ground flying faster than the speed of sound. By the time you hear the sonic boom, the plane has traveled a horizontal d3tby/ rwmj7fy 5 idwx9yr(eeanb p5(q.9 go13istance of 2.0 km. See Fig. 12–34. Determine
(a) the angle of the shock cone, θ   
(b) the speed of the plane (the Mach number). Assume the speed of sound is 330 m/s   


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82#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A fish finder uses a sonar defejd2s)ku5ot. l 2arrr 54d1ivice that sends 20,000-Hz sound pulses downward from the bottom of the boat, and then detects 2i5tsorfr4)jlr5ekudd a1.2echoes. If the maximum depth for which it is designed to work is 200 m, what is the minimum time between pulses (in fresh water)?    s

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83#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Approximately how many octaves are there in them2e ;n4uw /mzqwcrrt( + .y9jb human audible range?    octaves (Round to the nearest integer)

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84#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A science museum has a display called a sewer pipe symphonytj/ch ht)kg7v7 1rx n+cu38w x. It consists of many plasticg1/v wh k x3tux 87ncr7jt)+ch pipes of various lengths, which are open on both ends.
(a) If the pipes have lengths of 3.0 m, 2.5 m, 2.0 m, 1.5 m and 1.0 m, what frequencies will be heard by a visitor’s ear placed near the ends of the pipes?
f3.0 =    Hz
f2.5 =    Hz
f2.0 =    Hz
f1.5    Hz (Round to the nearest integer)
f1.0    Hz (Round to the nearest integer)
(b) Why does this display work better on a noisy day than on a quiet day?

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85#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A single mosquito 5.0 m from 4ssi0 ::oo hg2-x/sum c7zufea person makes a sound close to the threshold of human heeu4i smgszo0o:hfc2-u /7s: xaring (0 dB). What will be the sound level of 1000 such mosquitoes?    dB

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86#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the resultant sound level when an 82-dB sound and an 87-dB sound :cix:lf.03fi*qf k 3 ytd4zphare heard simultaneous 0lq:izkf3tpi:yh c3xf .*4fdly?    dB

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87#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The sound level 12.0 m frgus c ,,iwa)h0.ukma0d k- 1 bnwhc0a+om a loudspeaker, placed in the open, is 105 dB. What ia shwug0kmh.-c,1 wd, c+b kau a00)ins the acoustic power output (W) of the speaker, assuming it radiates equally in all directions?    W

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88#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A stereo amplifier is rated at 150 W output at 1000 Hk -q8 9)mxvui1bwbp* u9k d8dwz. The power output drops by 10 dB at 15 kHz. What is the power output in watts *9xipqk9k d)dmbu bu1v -88wwat 15 kHz?    dB

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89#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Workers around jet aircraft typically wear protective devices over their ears.7l gaeuv eq3;: Assume that the sound level of a jet airplane engine, at a distance of 30 m, is 140 dB, and that tgee vu :3a7lq;he average human ear has an effective radius of 2.0 cm. What would be the power intercepted by an unprotected ear at a distance of 30 m from a jet airplane engine?    W

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90#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  In audio and communications systems, 1s nlzk69w 7nsthe gain, β in decibels is defined as
β = 10log(PoutPin)
where Pin is the power input to the system and Pout is the power output. A particular stereo amplifier puts out 100 W of power for an input of 1 mW. What is its gain in dB?   dB

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91#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Each string on a violin is 9xvv/x0t5t ygtuned to a frequency 112 times that of its neighbor. The four equal-length strings are to be placed under the same tension; what must be the mass per unit length of each string relative to that of the lowest string?
fA =    μA
fB =    μA
fC =    μA

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92#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The A string of a violin is 32 cm long between fixed points with a funq5 j77+)sfzvkm g66ga 0rzdn pdamental frequency of 440 Hz and a mass per unit lengqd6567gksazp+ n0gv )7zjmf r th of 6.1×104 kg/m
(a) What are the wave speed and tension in the string?    ×102 m/s    N
(b) What is the length of the tube of a simple wind instrument (say, an organ pipe) closed at one end whose fundamental is also 440 Hz if the speed of sound is in air?    m
(c) What is the frequency of the first overtone of each instrument?   Hz    Hz

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93#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A tuning fork is set into vibration above a vertical open tubex:zi6:t eu+hyxb.y,bcty gq.. yzv5 1 filled with water (Fig. 12–35). The water level is allowed to drop slowly. As it does so, the air in the tube above the wi b1. q htzvytzu6e:y.x cbg+5:,y.xyater level is heard to resonate with the tuning fork when the distance from the tube opening to the water level is 0.125 m and again at 0.395 m. What is the frequency of the tuning fork?   Hz


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94#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 75-cm-long guitar string of mass 2.10 g is near a t+g fq 0ixk,)m ll:j.psube that is open at one end and also 75 cm long. How much tension should be in the string if it is to produce resonance (in its fundamental mode) with the third harmoni0jlilxsg ,m)+:kqp .fc in the tube?    ×102 N

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95#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A highway overpass was observed to reso5yx7ymny 6i, fnate as one full loop (12λ) when a small earthquake shook the ground vertically at 4.0 Hz. The highway department put a support at the center of the overpass, anchoring it to the ground as shown in Fig. 12–36. What resonant frequency would you now expect for the overpass? Earthquakes rarely do significant shaking above 5 or 6 Hz. Did the modifications do any good?
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96#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A person hears a pure tone in the 500–1000-Hz range coming from n1oymjcmhhye6uv6 dn*q 5ex v(7.,*ot0ir u; two sources. The sound is loudest at points equidistant from the two sources. To determine exactly what the frequency is, the person moves about and finds that the sound level is minimal at a point 0.34 m farther from one source than the other. Whc6n uemx6 my7tqo*nv 5vj0 *;i.e(h,1dyhor uat is the frequency of the sound?   Hz

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97#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two trains emit 424-Hz whistles. One train is stationary. The conductor on 3 kjb,tik/heq+m 4p x+w,a -gzthe stationary trai4 , /p,+- awgjzmexhqkk3+btin hears a 3.0-Hz beat frequency when the other train approaches. What is the speed of the moving train?   m/s

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98#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The frequency of a ste(tsjpy j3vx3 9/8j aniam train whistle as it approaches you is 538 Hz. After it passes you, its frv n3i98 ay3/ jt(xjpsjequency is measured as 486 Hz. How fast was the train moving (assume constant velocity)?    m/s

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99#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  At a race track, you can estimate the speed of cars just by listening to the dif rluu4 phhh*0ino 1/+(uqist3ference in pitch of the engine noise between approaching and receding cars. Suppose the sound of a certain car drops by a full octave (frequency halved) as it 30r pisihuu4 +h*/lt1(huonqgoes by on the straightaway. How fast is it going?    m/s

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100#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two open organ pipes, sounding together, produce 6fz-taa apz: vm*t2 /ra beat frequency of 11 Hz. The shorter one is 2.40 m long. How long is th mzzaatr*-6va/p2ft : e other?    m

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101#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Two loudspeakers are at opposite ends of a railroad car u0hrr bnrh;)0 v1k+a uas it moves past a stationary observer at 10 m/s as shown in Fig. 12–37. If the speakers have identicnhrr ;+krub0)v ha01 ual sound frequencies of 212 Hz, what is the beat frequency heard by the observer when (a) he listens from the position A, in front of the car, (b) he is between the speakers, at B, and (c) he hears the speakers after they have passed him, at C?
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102#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If the velocity of blood flow in the aorta is normally about 0.32 m/s what bea(m8uva5e2e4 bbf um d5u8go1 et frequency would you expect if 5.50-MHz ultrasound waves were directed along the flow and reflected fro2 fue u(b14aodu gmmebe5 5v88m the red blood cells? Assume that the waves travel with a speed of 1.54×103 m/s   ×103Hz

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103#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bat flies toward a moth at speed 6.5 m/s while the moth is flying )+etlwb/ :zt5z 7xush toward the bat at s+lz )ztxetb :5h ws/7upeed 5 m/s The bat emits a sound wave of 51.35 kHz. What is the frequency of the wave detected by the bat after that wave reflects off the moth?    kHz

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104#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bat emits a series of high frequency sound pulseoe 8 (38uyqb :6m7pkt,pulrits as it approaches a moth. The pulses are approximately 70.0 ms apart, and each is about 3.0 ms long. How far away can the moth be detec, 8t7k6q3yl t bepupmo(:ur8 ited by the bat so that the echo from one chirp returns before the next chirp is emitted?    m

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105#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
The “alpenhorn” (Fig. 12–38) was once used to send signals from one Alpine villayrg(gzad+a-(8 yk v; bge to another. Since lower frequency sounds are less susceptible to intensity loss, long horns were used to create deep sounds. When played as a musical inst+(bvyr8a-;k yg gzd(arument, the alpenhorn must be blown in such a way that only one of the overtones is resonating. The most popular alpenhorn is about 3.4 m long, and it is called the F sharp (or G flat) horn. What is the fundamental frequency of this horn, and which overtone is close to F sharp? (See Table 12–3.) Model as an open tube.
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106#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Room acoustics for stereo listening can be compromisfn8i/. n xzcvvb j-cb/va: cy-5i5e+bed by the presence of standing waves, which can cause acoustic “dead spots” at the locations of the pressure nodes. Consider a living room 5.0 m long, 4.0 m wide, and 2.8 m high. Cajcin 8-xi v ey5canbc-. b:/bv5z fv+/lculate the fundamental frequencies for the standing waves in this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

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107#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A dramatic demonstration, called “singing rods,” involves a long, slender alum+jtls/t ,2g9 z88jfdoma6rbc inum rod held in the hand near tb8 a jrzt+26o/9cg8d , lmjtfshe rod’s midpoint. The rod is stroked with the other hand. With a little practice, the rod can be made to “sing,” or emit a clear, loud, ringing sound. For a 90-cm-long rod,
(a) what is the fundamental frequency of the sound?    ×103 Hz
(b) What is its wavelength in the rod,    m
(c) what is the traveling wavelength in air at 20 C?    m

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108#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The intensity at the threshold of hearing for the human ear at a frhe2m838eqh 4zf 4cbsxequency of about 1000 Hz eh84 sh284eqm cxbfz3is I0 = 1×1012W/m2 for which β the sound level, is 0 dB. The threshold of pain at the same frequency is about 120 dB, or I = 1W/m2 corresponding to an increase of intensity by a factor of 1012 By what factor does the displacement amplitude, A, vary? 10a a =   

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109#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A plane is traveling at Mach g)3c 9bdpul0 0q ymsg:2.0. An observer on the ground hears the sonic boom 1.5 min after the plane passes directly overhead. What is the pla0lgpqy: sub)0g 39dcmne’s altitude?    ×104 m

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110#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The wake of a speedbosoyf.4zh h (bpoge iw me./*dw(-c 74yat is 15 in a lake where the speed of the water wave is 2.2 km/h What is the speed of the boat?    km/h

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