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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 sounok bhpvk1x9 oe 4,+.mad 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 formulj0:fe khc1zh uah98 i h.73z 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 homndm z)4p(nfx8i. fkwfd+ .d h:emade “telephone” by attaching a string to the bottoms of two paper cups. When the string is stretched and a 8 fdim+:pfdd.. 4f)n hz(w nxkchild speaks into one cup, the sound can be 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)(j9jkytw/k u krz-od- ;s( bg you expect the frequency or wavelength to chang y s(gktku)jj/wo- zr(bk;-9 de?
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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 giv 2j9i vtl. in8xj3c;eje that the speed of sound in air does not depend significantly on frequencjx 3ij8;i.e2vc 9jntly?
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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 vkk+uj;b(qh0 bery 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 tyf,o13v t9xcmhe 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 t,s qzb94.fu6sxv3k/im4jdh fhe amplitude of sounds in various frequency ranges. (An example is x/,3i9vfzjfq.k4udbsm h6 4s 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 guitar (Fig. 12–f4b 15vm gw7zi30) spaced closer together as you move up the fingerboard47 z5wmvg1ibf 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 behind a bive/ax-39 awr ud+o.muilding. 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. Explainu3ev -wdxo/a +.i9mra. [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 tos0o c;,ji2se fwe+.sl be due to “interference in space,” whereas beats can be said to be due to “interference in time.” Explain i2+e;wc. eslfs ,o0sj.
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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 speakers were lowered3wu* hug8x(kev0 p z//zw;5oku p zc0w, would the points D and C (where destructive and constructive interference;0cpo5/ux zzu(k 0u/vw 8*w3z khe wpg 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 protecting the hearing of people who work in areas wiovd5/2mzvl ae)(w-g4 db i2i kth very high noise levels have consisted mainly of efforts to block or reduce noise levels. With a relatively new technology, d/ 2)gdzb (5iw 2ov ma-i4eklvheadphones are worn that do not block the ambient 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. Each wave can bep8 pf0jf)4ix x thought of as a superposition of two sound waves with slightly different frequencies, as in Fig. 12–18. In whi0 x) ifx8pjfp4ch 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 s3 dc-;o y5x2nyr;cdp uource and observer move in the same direction, with the same velocity? Explain.c;3dd r5y uy 2np-x;co
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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 this alter the frequency of the sfr x+*g*kvh*f4ywxl: ound heard by a person at rek**gl4 w:hrx fxyfv+*st with respect to the source? Is the wavelength or velocity 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 positions j2abz7 ue*zpc7sghl) 2-j 0a2n zdt/nof 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 reasoning. 7us2 ja)n2 l20 z- e*ab tzjzdchpng/7

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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 for thec,f2u2h :ltauf9n w- c echo of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.0 sfut2:9 l- c,2ac nwfuh 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 thghwwn4jf )uw03va y3b(k+cc2 e echo of the sound reflected from the ocean floor directly below 2.5 s later. How deep is the ocean at this point? Assume the speed of sound in seawater is 15gy 2 )ww jv w04h+bc3afcu(n3k60 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 wavelw jwj zzt(-pu+.m bj x.k83c3dengths 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 sch n4a2.ht/x:8-amtjfyc al f,c ool of tuna on a foggy day. Without warning, an engine backfire occurs on another boat 1.0 km away (Fig. 12–33). How much time elapses before the backfire is heard (a) by thj24cf a, yct-ma8axftl: hn./e 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 whe; aaqy0y;ddis82 -at bn striking the water below is heard 3.5 s lasy2a dbdia ;t8-;qy0ater. 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 the ground, sees a huge stone sto z uj(5 djyel-2/uf3krike 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 1.1 s apart. How far away didzy- (l/3uu 2f dj5jkoe 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 one mile )bbhdd k s 6zff8 er5u/ah:3x+of distance by the “5-second rule” for estimating the distance from a lightning s/ ah3 rbudbf6s )hxd 8z+f:5ketrike 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 pain level of 120ilh+gi wr4d8 q.)sb 5ib7a;yj 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 levu qz-; oee6x4sel of a sound whose 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 leve xmtg4xm7ojwbr o4))l 1g:rn: l of 95 dB when fired simultaneously at a certain place, what will b4xg :nrg:xjol 7)m4twbm1)ro e 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 c*lvuu6( (woli hd /+09wilmgy ertain distance from an airplane with four equally noisy jet engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person experience if the captain shut down all but one engineouuh +(6llg/wiy mw d( *90vli? [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 gq9- qvja/l/whp y+:x8gm g*hratio 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 ea g /h+/xam*wjq9:qgygph8v l -ch 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 sounjbv e ob9h7 bt5,r1us-d from a person speaking in normal conversation. Use Table 12–2. Assume tbb159evbuoj, -7th r she 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 eardrum whosezdx4;t.xx q-nh4 r/pa ocy8( h 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 morenz3qw rv08gm- modest amplifier B is rated at 40 W. -vzr8 03 qgmwn(a) Estimate the sound level in decibels you 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 registere,tpx0 pkaz3zkb: l86e 2yz+xrd 130 dB when placed 2.8 m in front of a loudspeaker onk +:k6rt8zeazbzy xx0p2 ,pl3 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 detect sx0jcx. 8o(q-bczb5 ta difference in sound level of 2.0 dB. What is the ratio of the amo0sjtc(qx8 cbzb.5 -xplitudes of two sounds whose levels 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 ajm:mj5 q.z) xlf:z/) onrc 5xu sound wave is tripled, (a) by what factor will the intensity increase? Ixun )5 mjj/lmz.oc::z) f5qrxncrease 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 displacemnx ewk,)7 6bg,hdqt2k*czf q:ent amplitudes, but one has twice the frequency of the other. What is the ratio of d gth n7)2q :6qk*b,kfzew ,xctheir 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 gug7bftmfyc+8l)f25 level (in dB) of a sound wave in air that corresponds to a displygf 7+fmb 8c)tf ul25gacement 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 what sound level to seem as loud as a 100-Hz ton(g o 9u3hcthom5s0t x9e that has a 50-dB sound levet 0mc9hx o9s( tog5uh3l? (See 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 highe)etfw pkmw0 (frt5 x;/st frequencies that an ear can detect when the sound levelewtf;0p t/(k w5 f)rxm 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 eh,4/lrlsm hptelff29- s 5:g range of sound levels. What is the rati l mef2: ftehslh59pls,-r/g 4o 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 Hz. Th 7*l)rcy.be cpe length of the vibrating portion is 32 cm, and it has a mass of 7eypcbrcl*) .0.35 g. Under 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 fundamental and first three audiblhajd ,6 s btl,f*sw57be overtones if the pipe 6,db *,5fbsh7ts jawlis
(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 frd dti9b2wo-:i0j xu3iw/yk.io e5-rry.(v pyom blowing across the top of an empty soda bottle that is 18 cm wxydy:k- y -tvi pbow0ji9.(ou2ed.5 r /rii3deep, 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 range u68on,j.lg-opcocb/ a :ef 0cof human hearing (20 Hz-8a 6,o: of n p/ucojcge0lc.b to 20 kHz), what would be the range of 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 9 gfv kyt1d6z9of 540 Hz as its third harmonic. What will be its fundamental frequency if it is fingered atv9 t6 9kd1zgfy 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 long and is tuned to play 14y9fega6fdf8f x9,h k . qarzE above middle C (330 Hz) a z8kh9rf ed,fa69f.fyxq41g.
(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 opegj ;o. 9xx4 bk7jdv(sen organ pipe that emits middle C (262 Hz) when the temperature ikg;ejs( 4oxd7bx vj.9s 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 bx2qhcp/ flyt ba4027at 20 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 flute in Example 12–10 should the a a6y04smcw1 rzhy4p, hole be that must be uncovered to play D above midd1h 40,4p a6zyscaywm rle C at 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 264 Hz, 440 Hz, and nj-osi e4/ k7s616 Hz, but not at any other frequen4-es7 jkoi /sncies 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 5 )0o-d-ygi9 wj vlhuwopen at both ends. It resonates at two successive harmonics of frequencies 275 Hz l )i9wv-d0y wu-go5hjand 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 mt 7-i yo4m76 dmp*sgz 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 au,i.)qiyx,laqe h. xx6 dible range for a 2.14-m-long organ pipe ayxq),e.qalxi6x h.i ,t 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 outsideyrmos fk 1,c*3 and is closed at th*fyc3 o r1,mkse other end by the 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 h;cbq/abj/hb*o c k;2to adjust two strings, one of which is sounding 440 Hz. How far off in frequency is the other strb//q *;2chakh;ocbj bing? ±    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 (262 soa( l2 rp;a8u bljw4ii;n 5z e35xk3bk4o( rgHz) 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 anoth/ / h7zi,trxe4:4ojzeg piko8er (brand X) operates at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whine of frequeni4:o/ixtr ,z8 heg/4j7peozk cy 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/o0j gyq+624dpht08rp tr eu -ms when sounded with a 350-Hz tuning fork and 9 beats/s when sounded with a 355-Hz tuning fork. What is the vibrational frequency or0u4 gttdr0p-2ho+m 8j pe 6yqf 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 tu ekbwoi4; ;)mnned to the same frequency, 294 Hz. The tension in one string is then decreased by 2.0%. What will be the beat frequency heard when the two strings are played together? [Hinbi;; kew4mo )nt: 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 flutes each try to play middle d2jg03 cemcotx dn 92*C (262 Hz), but one is at 5.0°C and the other at c90cn xgj 2m23dt od*e25.0 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 m3tij;dni4 d f,at)y :forks, A, B, 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 p:3ta idtm4 f, jdy)in;ossible 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 speaker73g6yhz: e:4lj)(gp k mf irru and 3.5 gp3:rhfgmj e47z)(kur iyl6: 0 m from 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, but a piano tuneddsy1n :v9)m yr hears three beats every 2.:9)mvns1 dd yy0 s 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 wavelef(p6/ic ,ojw angths 2.64 m and 2.76 m in air. How many beats per second will be heard? (Assume c,fja6 iow(p /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 sire)s u+6(- h*typzoij(aq yjxb 6p8rv*un is 1550 Hz when at rest. What frequency do ypjqzorj(u - *6( )y*+ pxtyv8uis bh6aou 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 zel2cbv)0nhqs 0wea4w:d ct tq e*d 1:f6w/r5frequency do you detect if a fire engine whose siren emits at5vf /0 we*w 2):se:t1ccn w4dzqbtehr 06dqal 1550 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 youge me :-11e2 pviv wl(ph+(tb ;uaj)kv at 15 m/s versus you moving toward it at 15 m/s Are th+-h (j mpuv( vetle1;vg: be ia2)1pkwe 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 s4 uk x+9jnqkj.ingle frequency horn. When one is at rest and the other is moving toward the first at 15 m/s the driver at rest hears a beatk.qx+j4nu k j9 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 waves at.o2dx p3dcs, j 50.0 kHz and receives them returned from an object moving direc2j3docpxd s.,tly 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 ofiga35mkw ewtl2y, i73q 6((9ijmm knl 5 m/s As it flies, the bat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency does t59((2i3 ma ,i3 gmlt ynlwmkikwq 76ejhe 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 experf r; m9b2th/zwiments, 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 while at rest in the railway station. What beat frequency wa2;t r /mf9zwbhs 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 to measure blood-flow speed6;6 ;k pfbkpyf.,)1jxnjru sjs. Suppose the device emits sound at 3.5 MHz, and the speed of sound in human tissue is taken to be 1540 m/s What is the expected beat fryf;rpb,jx)s6j;ku j p.n6f 1kequency 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 w 1h:xaf /rafub-f7 p2h5u lt1gr/nn2xaves of 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 frequenc 8r/ vj0ty um88;tmcwah s9e8cy 570 Hz. When the wind velocity is 12 m/s from the north, what freqce v 88;8yrtmcaju8smw/ht90 uency 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 moving on land l3, o+ezu il2nif 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.cocn mzn+3 f3 where the speed of sound is 310 m/s (a) What is the angle the shock wave makes with the dirnc.3zon+ mcf 3ection 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 m3mfqp).gx2p+3fu./m ftzuoplanet where the speed of sound is only about 35 m/s mf.pg+mo3f )uxf3umz2 . pt/ q
(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. Determineo8. *hr48 ojpc i;)dxey* zgde the shock wave angle it produc)dz*4o gei;x*.yro8 hcd p8je 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 h1 j cuv 4x0,gh1 vka,j3v)lzz/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 1.5 km above the gr4byt7svye y4 98xt;. qgkrj2w du j/)yound flying faster than the speed drt4)ekqwy;7t 2 9u/g sbvy .4xyjy8jof sound. By the time you hear the sonic boom, 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 sendsh+ +zf:e* wb kcndh)9u 20,000-Hz sound pulses downward from the bottom of the ebh+ kn u)+ f:*dhwcz9boat, and then detects echoes. 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 thssw6r (zm1p kt.d ax)m5y. ,fwere 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 display called a sewer pipe 99zyhl.,2hg x(mtonysymphony. It consists of many plastic pipes of various lengths, which are open oym,x2n y t 9lgo(hz.h9n 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 mak i/* 7hy)lskpies a sound close to the threshold of human hearing (0 dB). What will be the sound level ofih pl i/*s)k7y 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 sound0qkf,2pr1ah62yn: 2m;:d g yiw jya pnwn 3yz1 are heard sazy0 nw; :f2ny ykyr12312, h iw:npgqamj6pdimultaneously?    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 meff:.;uq0cep from a loudspeaker, placed in the open, is 105 dB. What is the acoustic power output (W) of the speaker, assuming it radiates equally in all directionc eeu. 0q:pf;fs?    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 1ov ;g) w:n:nuq7 v9rad50 W output at 1000 Hz. The power output drops by 10 uwaorng : ;7:nq) vvd9dB 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 aircraft typically wear protective deva g2d)o.jpm9s/2ehmf bk:s k0 ices over their ears. Assume that the sound level of a jet airplane engine, at a distance of 30 m, is 140 dB, and that the average human ear has anshk.p jg/a90omb)kef2s : d2m 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 systemsfsxl sd v*xm-d +ad2wh:2mb)+, 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 au(nzw;, fb0x*larm6v (dqsi8 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 points3bia3: im 7oi+r(hcui:1ww wwy ry9b* with a fundamental frequency of 440 Hz and a mass peyy3m7 bw:ir ahw3r wboi*19iw:c i (+ur 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 open tub dsq4qwx-70 n3p l+usz6 gjd*he 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 leve3gz6dl*d+ujq74sspq -x n hw0l 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 tube thp4wol 3f6 bzhd:1;lb eat is open at one end and also 75 cm long. How much tension should bbo6 l 4f1lwbh3ez:dp ;e in the string if it is to produce resonance (in its fundamental mode) with the third 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 observed to resonate as one full loo6bne or )1p)mfp (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 5p 1m1 g zkjbj+13.wpnmb,e6cl00–1000-Hz range coming from 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. What is the frequency of the so. j,gknzjbb +6mlwp1c1pme 13und?   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 whi7)i+d8c dfw uzstles. One train is stationary. The conductor on the stationary train hears a 3.0-Hz beat frequenc z7)+fd8cdu wiy 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 steam train whistle as it approach byajh7u*.e)e ) wwdj+ rt2)tnes you is 538 Hz. After it passes you, its frequency is measur)a j.w2*reju wd)7h+tt )yeb ned 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 cars22 ogyf. x.qce just by listening to the difference 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 goes bf.o2y .gecqx2 y 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,tgf ,*h9nw2vs produce a beat frequency of 11 Hz. The shorter one , vg fnh*t2sw9is 2.40 m long. How 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 opposite ends of a railroad car as it moves p xjiw+:tdl7e.ast a stationary observer at 10 m/s as shown in Fig. 12–37. If theji: wlxt. +7de 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 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 thev(*ljk r,ex:( to(xv+i vn 8fs aorta is normally about 0.32 m/s what beat frequency would you expect if 5.50-MHz ultrasound waves were directed x(itv :xn v r8of, k+sj(vle(*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 moth is5aqq0d+9 ( ta2wjxft q flying toward the bat at speed 5 m/s The bat etj0 a q+ qwxq9a5dt2(fmits 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 soulb 1nqtxa.e ,1nd pulses as it approaches a moth. The pulses are approxqn1 a xl,1.bteimately 70.0 ms apart, and each is about 3.0 ms long. How far away can the moth be detected 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 onzk/i,5o2oks le4fdv, e 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 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.) Modoi,5kk,2 e 4d/zlfvosel 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 compromised bylmxp4og,y : o: 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. Calculate the fundamental frequencies for the standiym:xopo:4 g l,ng 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 r-cqpjqik:cn 7 4 66flaluminum rod held in the hand near the rod’s midpoint. The rod is stroked with the other hand. With a littl7n p4ck- ir6qqc6lj f:e 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 freq .plusj(fr 12oy am:i0ibay.7r.fqc;uency of about01ijaa f.ic27 up. b:sry(;mrf .qyol 1000 Hz 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)pwm-sde13)(s r01jpcw;fp 1dij zgk the ground hears the sonic boom 1.5 min after thed(m pres3)-zg pf 1 jws;ijc)01k1pwd plane passes 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 speedbov9ph,, q(+te s9b b/muf-clwjat 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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