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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 .rs;yk8 fjlr: zl x ca06;4mjvthat sound travels 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 is a form dsb*as 2xa)o /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 “teq vxl4itr7r+; dy:+myl : f8bjlephone” by attaching a string to the bottoms of two paper cups. When the string is stretched and a child speaks into one cup, the sound can b+q+ml:r dblr y 8x;f74 vj:ytie heard at the other cup (Fig. 12–29). Explain clearly how the 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 fhj84by( x:(y d: 31fenp jcvtdrequency or wavelength to chab3ft8e cypy(jdxhnj(: v1:d4 nge?
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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 sound inde8a cue0 d)):h2 zux skpjc) q-vp5to,3rh9j air does not depend significa5 ko ua3hp9,c)et2e dxsc jp )h-q80v)ru:j dzntly 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 sounds very high-pitched.ltgn. fu1 ,o5p 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 tz n 0n00tf)liuhe 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 x 8qic jx h;z8i-y9:ptamplitude of sounds in various frequency ranges. (An example is a car mufflyitzp :;x i-8hqcx8j9er.)
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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 guitar (Fig. 12–30) spaced closer togeth7(t4 mw5bahh cfy8*fc :asyg7 er as you move up the fingerboard toward t4at(5hfycsb7h cwf8g 7 y* :amhe 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 behind a building. Initially you hear it but cs+q;i )jpriu-bg,9btg ;mie,annot see it. When it emerges and you do see it, its sound is suddenly “brighter” — you hear mores i qr b);itme,;pu,j-ibg g+9 of the high-frequency noise. Explain. [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 due to “interfzypjvq smi :8v:4+ 1ererence in space,” whereas beats can be said to ::4mrq 1j yvevzs8p+ibe due to “interference 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 of2), r bndqh w2esihb/: the speakers were lowered, would the points D and C (where sh :bw/22 bhnerqi,) ddestructive and constructive interference occur) move 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 protectiqcs :(zbuz 1 8vp)e/39nrq8mjej h5dyng the hearing of people who work in areas with 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 ambieheu8:z/)1 dcq8bn q5(r yjmvp93 sjeznt 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. 12–3le1)ne791wx;c zxr rmm1u v08xdl)x l1. Each wave can be thought of as a superposition of two sound waves with slightly different frequencies,;cn)9xru xel d 107mex1zrlvx 18w)ml as in Fig. 12–18. In which of the waves, (a) or (b), are the two 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 and observer move in the same directionmz1h9 x;2ig jbb;w w9v+lar r*, with the same velocity? Explah gi+;9*b ra bvjxw2w 9;mzlr1in.
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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, wi5ta87ly(8y jun mj8djll this alter the frequency of the sound heard by a person at rest with respect to the source? Is the wavelength or velocit8dn8al(j j578mjy ty uy changed?
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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 posi 27 cq1u(ju(txrdz-c qtions of a child 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, will the child hear the highest frequency for the sound of the whistle? Explain your reqd2 uc 1qut7(r-c(j zxasoning.

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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 length of a lake by listening 4rvi-z4yjo; ;dla/ p bfor the echo of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.04;jvao i4zp/ y- dlb;r 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 vmx.3s3m./ v yp,ypp/ 0 swinoa9z p(r6ises2 echo of the sound reflected from the ocean floor dir0y. w sizemx9ippn 63(sov/ v s,m3rppya2./sectly below 2.5 s later. How deep is the ocean 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 wavelengtx: /hu//ewk ej* tt4wjhs 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 school of tungo, *lv3f.p ava on a foggy day. Without warning, an engine backfire occurs on another boat 1.0 km away (Fig. vo.pa*fl g, 3v12–33). 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 kg q9)ncv1))4 vv1dnh rtdz 4ya cliff. The splash it makes when striking the water below is heard 3.5 s later. How high z4rk n gq9)d )1vny1tvc)4vdh 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 the ground, sees a huge stone strike the con4e bbn4 zmf3+hcrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other in the concrete, and4 emfzn3+4hbb they are 1.1 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 percenttnq9u2vz ,e*i error made over one mile of distance by the “5-second rule” for estimating the distance from a lightningnv *z ,u9q2tei strike if the temperature is (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 p q nl b,s9t1egm3ko-7dain level of 120 dB?    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 inten dw:eu ,1+mq *oxqbn4 3(mrpajsity 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 levesk2l00m 8q jjli8aj5 il of 95 dB when fired simultaneously at a ce l 8isl2jjiaj8m0q0 k5rtain place, what will be the sound level if only one is exploded? [Hint: Add 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 dis..ow3upb w m(w 5 c( lklg9rp8fqck,v8tance from an airplane with four equally noisy jet engines is expebvlp.c8.9wqg3w(f 5umw co ( kkp8lr ,riencing a sound level 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 signaskr/c10 pl+ , w9gug:oknk0mal-to-noise ratio 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 k/gc: nk,r0pw+umsag 0 l19ok each device? 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(cy up/ddbjs0-ga isyiyl8y r( 78 .t: from a person speaking in normal conversation. Use Table 12–2. Apsagj:d8 yir.(c0i(7yst- y8dlb yu/ ssume 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 an ggc)h *f sa10beardrum 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 modest amplifier B is ra5*iu c-0;(kg/8 zp cvvajx aovted at 40 W. (a) Estimate the sound level in decibels you would expect at a point 3.5 m from a loudspcj0a -(8vugiv/ c5z* kxv;apo eaker 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 13c6u;gf 9b h5gl4j e2cz0 dB when placed 2.8 m in front of a loudspeaker on the stagec;h ucge 2zj4gl 5f96b.
(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 detect a difference in sound level jlo7yy5veifz3 3yhi.+- wb-qof 2.0 dB. What is the ratio of the amplitudes of two sounds whose levels differ by this amount? [Hint: Syev- j iyl.ziqyob- fh +57w33ee 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 the intenc-xvgr: j4 wz9sity increa9z4grxv:w j- cse? 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, bwaez *g6k ywy )4s3hc(ut one has twice the frequency of the other. What is the ratio of theck(4ze3swha6y g)w *yir 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 level (in dB) :dz:.l nv;7m y4bar nputb71kof a sound wave in air that corresponds to a displacement amplitude of vibrating air molecules of 0.13 mm at 3004k7dyn.r;uza tb 1:v mn7:pb l 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 what e,fp1ab2ieu:s 8 /l n tl::cajsound level to seem as loud as a 100-Hz tone that has a 50-dB sound level? (c jten8ulpabf2: 1l:ia, s: /eSee 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 j.fbtx4mip o,6lw3a (an ear can detect when the sound level is at, 6mpwxb j(4f3ol.i30 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 ac qwyj,50e-lzyf,tu .ncommodate a huge range of sound levels. What is the rauyf wyn0j,t lq,-e.5 ztio 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 fundamentaray( rw l.+k8vl frequency of 440 Hz. The length of the vibrating portion is 32 cm, and it has a mass of 0.35 g. Undeayrl(rvw+ k8.r what tension must the string be 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 fund9 w 3ant( 3wkrj)kwos-amental and first three audible overtones if t jrw3w 3kk9nw-()oa sthe 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 frequency would you expect from blmj t tjycnf:5p l51/xsa*n//cowing across the top of an empty soda bottle that is 18 cm deep, if yon5:5st/n pj/cxatcf 1lj*y /m u 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 pivxjwqe*mq2 p49cd +m2 pes spanning the range of human hearing (20 Hz to 20 kHz), what would be the range ofdmc29*e+2 qv pjw4mx q the lengths of pipes 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 i ;1 vqks/bh-0 hplyp9of 540 Hz as its third harmonic. What will be its fundamental fre-h0ypilq;p 1vs9b/khquency if it is fingered 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 0.73 m lon oyv jkg)w0q4)g and is tuned to play E above middle C (330 q)gv) k0ywo4jHz).
(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 o o;m hw-kzl,,ne91 zqipen organ pipe that emits middle C (262 Hz) when th, zzoqh kn,1l9-i;wmee temperature 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+-igi7r y ,cuu1tf m irg;3mo* 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 mouthpiecvo9ju kyl2i o/1p1gi8e of the flute in Example 12–10 should the hole be that must be uncovered to play D above middle C at 294 Hz/ y goo1ipv k81l92iju?    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 264 Hz, 440 Hz, vq ma2l5( y5qgand 616 Hz, but not at any other frequencies in between. (a) Show why this is an open or a closed (qyq 2mvla5g5pipe.   (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 lodaepx5:r ;x 1z (y2svakxf-x yq2*1mbng is open at both ends. It resonates at two successive harmonics of frequencies 2b5p21 qmaeszf :*2avd yy;xxx(1x-kr 75 Hz and 330 Hz. What is
(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 uz9qx)n k4p,r 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 jzauq,)s;dcr- yp0 ulv /a97d range for a 2.14-m-long organ pipe z ;s7uv0dlaqc yjr/9-pa,ud) 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 approxima*v-c/khw tx+m tely 2.5 cm long. It is open to the outside and is closed at the other end by thvcm*- hk+t/wx e eardrum. Estimate the frequencies (in the audible range) of the standing 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 every 2.0 s when trying to adjust two strings, oney-gnu7x x(qzzkqcy) 6p81 o f5 of which is sounding 440 Hz. Howq f5 p)x1ugyo7-z68cy(qnzxk far off in frequency is 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 frequencsth/g2/dj- )tq 4u 9ix z3mf mvaxo0g.y if middle C (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 ativw rxe+ur; .5 23.5 kHz, while another (brand X) operates at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrvei;urw x+ 5.rill whine of frequency 5000 Hz occurs when they are played 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 w k5 i:ewqp/wqt:bi ,v)hen sounded with a 350-Hz tuning fork and 9 beats/s when sounded with a 355-Hz tuning fork.5ewbtiiq: q ,p) vkw/: What is the vibrational frequency 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 tune/32 oxgebc9hw ; p ctj.(xuba:d to the same frequency, 294 Hz. The tension in one string is then decreased by 2.0%. What will be the xpw o.3:ua2gctc/(; bh9ebjx beat frequency heard 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 flute acs9a+m jrrdlfog/q.*w-asym n,*v ,/ kq3m-s each try to play middle C (262 Hz), but one is at 5.0°C ms/ad/g+,rko wnqaq3lf-m-9*rys j ca*v,m.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, d( prk,*via.sB, and C. Fork B has a frequency of 441 Hz; when A and B are sounded together, a beat frequency of 3 Hz is heard. When B and C are sounded 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 tog. ak vi,sp(dr*ether?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+p*;w v 4xgzos1dyb4f . A person stands 3.00 m from one speaker and 3.50 m fromz wv *sg+; o4by1df4xp the other.
(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 Hz,ecd:1raw fu6i .5 tx4r but a piano tuner hears three beats every 2.0 se65x41iarfr . tw:c du when they are played together. (a) If one is vibrating at 132 Hz, what must be the frequency of 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 m in air. How many beatonusz 3ty3jz b)xfm( wxc03k u:/69gws per se3 cbwzu )3fu6g 0( kjo93ntxswxmzy:/cond will be heard? (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 of a certain fire engine’s sireniax3 5 )0znpzr*ydv4 d0mjc1 q is 1550 Hz when at rest. What frequency do yoyd)xrc zmv 5q3n41d 00a*zjipu 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 stihhj-*n --w iozno qr q:kg*:;ll+q 7qoll. What frequency do you detect if a fire engine whose siren emits at l -*:q;lzonqn h-7r*hgj- oiqo qw:+ k1550 Hz 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 you at zy szp qj1t 30z2wk -22ubq7dg15 m/s versus you moving toward itq wzkzg07p-2 q31d u2y2zstjb at 15 m/s Are the two 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 same single frequency horn. Weiyyu 13/c 7ljhen one is at rest and the other is moving toward the first at 15 m/s the driver at rest hears a beat frequency of 5.5 Hz. What is the frequency the horns emit? Assu yl j/yiec7u13me 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 waves at 50.0 kHz and rec :s lb:o3 tw4cl;zpi6v9i2irdib)*h oeives them returned from an objlw v ;d9) l izh:pob*t3irbi2cis6o 4:ect moving directly away from it at 25 m/s What is the received 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 wall at a speed of v0jjvtzm.ecd a3+-uon+d :h .5 m/s As it flies, the bat emits an ultrasonic sound wave with frequency 30+cddnvt: jo0az3h u-.m.vje+.0 kHz. What frequency does the bat hear 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 Doppler experiments, a tuba was played on a; co*job(zoy,h gb179iqj ;dh moving flat train car at a frequencyg7;,(hb9i odz o ;b jh*jqo1cy of 75 Hz, and a second identical tuba played the same tone while 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 ultrya q+ a:6m(da ,e2abuzasound waves to measure blood-flow speeds. Suppose the device emits sound at 3.5 MHz, and theaze+y ab2u dma( qa6,: speed of sound in human 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 ofj (lo)vhmjp 9zwp9e)z48:ix y frequency 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. When the o-jqm(g:e0)j .3t +b83jdhu fc,cl bc c:naigwind velocity is 12 m/s from the north, what c38(g0j+l : , -jj qgtdmb3aob. cif :u)cnechfrequency 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 movk; 1y,y:a nm2bixcxeox)5 de )ing 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 speed of sound is 310 m/s (a) zzn91 rgud )-kvm8(:y is0s*;hpw nzp What is the angle the shock wave makes with pgn z8swz;vsm pnyz)r k91* (h0u-:idthe direction of the airplane’s motion?   
(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 planet where the speed0o)ieie n3eu/ of sound is only a/ui0e 3n eoie)bout 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 oo8uel 1e-q(fq.5zz 9xfn q2htcean. Determine the shock wave angle it produc-tn .qf qx92zoh(15e zelquf8 es
(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 t q9hlo;;pf rt1ulp3 4/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 overhe5m)xp /q: 3u) ba4zin+3i tcg hsj08dm uto;ttad and see a plane exactly 1.5 km above the ground flying faster than the speed of sound. By the time you hear the sonic bo)q ptg5ix mjm8bcus):4u z0 t;3hat / otdni3+om, the plane has traveled a horizontal distance 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 device that sends 20,000-Hz sound pulses downward frowe+2twfx sf r g817 :82bz hpe+w6hqzzm the bottom of the boat, and then detects echoes. If the maximum depth for which it is designed to wors2:xb7 6 fh8wegw++21q z zpeh8trwzfk 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 octb :lyztvyw7d jr0( y6b7h)v ;javes are there in the 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 d4u e3h5v:u 8rgp i.purisplay called a sewer pipe symphony. It consists of many plastic pipes of various lengths, which u 3p5iv.4h gpu8eu :rrare 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 a person iyam -5kp i+i 04-xi /9c*sh8v besgobmakes a sound close to the threshold of human hearing (0 dB). What will be the sound level of 1000 such mos *-x4is a/ikhiv 5ebbyi0 p+- 9ocgm8squitoes?    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 lev30ctqq .7ma byel when an 82-dB sound and an 87-dB sound are heard s.mb0t73aq qcyimultaneously?    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 fromqpg h627,vld tdsv.2 q a loudspeaker, placed in the open, is 105 dB. What is the acoustic power out sdhvq ,6gvd lq27p.2tput (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 1fj l;/o1zfp56eepp d 550 W output at 1000 Hz. The power output drops by 10pep l5 e1 fj5fp/;zd6o dB at 15 kHz. What is the power output in watts at 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 aircrar hc) (vz;6vbflwc5e 9ft typically wear protective devices over their ears. Assume that the sound level of a jet airplane engine, at a distance of 30 m, is 140 dB, and that tv9)wcc b;6ze5lv f(rhhe 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 communicatio*ikx f) .kyu6 tx)mca1ns systems, the 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 tuned to a frequen;dpo ++6n q,kk0ws eqmcy 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 cra ,g2 x/z;opivg2s0um long between fixed points with a fundamental frequency of 440 Hz and a mass xirv2;pas, g/2zuo 0gper unit length 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 ope c48u/)3empcfg 4 v4re xzuy(qn tube 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 water 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 fr /uexyv43)qrc mzegc 8p44(u fequency 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 str;qtkik aq++f/l*se86s f*ez hing of mass 2.10 g is near a tube 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 a 6/seqzf8*tl+;si* e khk+f qthird harmonic 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 obssde /ag5nlj:q;w6uk9ff;:aq 6nby j 3erved to resonate 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 a9 kusmpxp -38from two sources. The sound is loudest at points equidistant from the two sources. To determine exactly what the frequency is,p-s9p mak8u3x 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. What 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. kut7yxbf;zzap v)ih *ch9w33 f2p6g2 The conductor on the stationary train hears a 3.0-Hz beat frequency when the other trafhcizubzyg ahktp) 732 p3;fv62w9*x in 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 steam train whistle as it approaches you isle1:d+s3yvb n3 ,sbu a 538 Hz. After it passes you, its frequency is measur3ba+su:3 ys,e bvl1dned 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 estim uqn5r 3/-ubxpate the speed of cars just by listening to the difference in pitch of the engine nonx b3rp-5quu /ise between approaching and receding cars. Suppose the sound of a certain car drops by a full octave (frequency halved) as it goes 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, soundingh)/ .edk/eng+lezw2 m together, produce a beat frequency of 11 Hz. The shorter one is 2.40 m long. Hog eze dh)k.2l/nm +/wew long is the 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 oppo(h zu2w*n s06oru mc:ksite ends of a railroad car as it moves past a stationary observer at 10 m/s as shown in Fig. 12–37. If the speakers have identical 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 afterm0 oh k:unwrscz(u*26 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 nor5 x5 ig;pvh.3lkihd,d 7zlr (umally about 0.32 m/s what beat frequency would pdizi(ukl. 53dh7;, vxh r5lg you expect if 5.50-MHz ultrasound waves were directed along the flow and reflected from 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 mot /dlqtouth4y:2f9cu(6m xufcr/ db,0h is flying toward the bat at speed 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 ru2y(/:db u,ctludfmxth4qr9/ o cf6 0eflects 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 pulses as it approache:dayls y: 6cvy;s 0mw5s 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 detected by5cs yy:svdm:w6;0ya l 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 signh*1xt fi 9t6iho0 c,n:gb 5oduals from one Alpine village 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 instrument, the alpenhorn must be blown in such a way that only one of the overtones is resonating. The most popular alpenhorn is abou1 ,:o ixh65 dfibhotg *n9tc0ut 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 bec)6kya3*zai4 yqbz,tn1 y8eyq4bx z 1 compromised by the presence of standing waves, whiaybyikte yzy)cq 31 8a 6z*xzq4,41nbch 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. Calculate 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 zu9yjqw 9 dt9.w)dv/u“singing rods,” involves a long, slender aluminum rod held in the hand near the 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-longwddtquvy w)9zj9/u. 9 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 frequency of ka8ua qy b fo996z:;mbabout 1000 Ham6 ;k8bub 9zq:ayo9 fz is 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 2.0. An observer on the /p.d l;g9bfh w4)y)l qn yypg*ground hears the sonic boom 1.5 min after the plane yhwn4y;b y d ))lfg 9/g.*qpplpasses directly overhead. What is the plane’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 speedboat ibm2kyr(4 epe*9jzfud( /a-0oktm; fi s 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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