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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 travels as t7kb3zs ( pw mha;+x.za 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 94mdvc;f d dn*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 attaching a string:;gb l)6mvfjm 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). Explai:vm6 f;)jlgbm n 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 passevflu o*,zn; t+n4w/g2l qxer ,s from air into water, do you expect the frequency or wav+vlwxn2 4q *gnoe,z;t/fu ,rlelength 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 sound in 6kve vozcn vx5 bj/d4r+f;z6/air does not depend significanvv64+f z6ndv/c;j/ kz b5ox retly 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. u27a f:38z62egykxs5iy4+ ffkef poy 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 temperatzrjj,+,w 0g:z/v) tno nnzq hc+so0 7zure in a room affect the 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 amplitude of sounds ib.wd/s( a 7t d)f2pu: ttmyu k;q.kd(cn various freqp;((md bstatukwcdtf/k y.u ) :2. dq7uency 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 guitar (Fig. 12–30) spaced closer toge5 ojh;d ed1jg.ther as you move up the fingerboard toward the eohdj .; d15jgbridge?

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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. Init.ekz bgtaz5i4ve xjvz t/ )3:,ially 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-frequen,ztz. )z:k3e 4ebj5ig v vt/xacy 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 “interference in space,” wj4+iz +0 uaienhereas beats can be said to be due to “interferencejz4 en0+iaiu+ 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 speakers were lowered, would the1- uq8 liicw1x points D and C (where destructive and constructicw1iq1 -ixl8u ve 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 protecp9+xhj* 7 itekting the hearing of people who work in areas with very high noise le i+xh*jpe97kt vels have consisted mainly of efforts to block or reduce noise levels. With a relatively new technology, headphones 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 stv+ 7rp,-hll.jy* cs shown in Fig. 12–31. 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)shj v-t rly*,p7.s+lc, 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 id emf c2vdmy2t9: q/brkj, 1;f.tqv.mn the same direction, with the same velocity?.emqm:.,kmjb y2tfddr9cq1v v/2t ;f Explain.
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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 altelowehq9gg9jl w f sxj+b)89b90 f4n d/r the frequency of the sound heard by a person at re jwblgo8j+4 fn9lq9x 9ws dfge 9bh/0)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 of a child in motion on a s; e7cqclgp7g hv w22td0lcdl;u .y6;fwing. 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 7lhecc t620;qwg .v2c;d ydu7glpfl;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 length of a lake by listening for the echo omb, 0cthqb d0b;rs(tu aj755zf her shout reflected by a cliff at the far end of the lake. She hears the echo 2.0 s after; b7hca st5b(j,5dz q 0br0utm 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. H2 :co (1lnre w8-mpvbpe hears the echo of the sound reflected from the ocean floor directly below 2.5 s laterec1norp(v -8: mplbw 2. 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 wavelengths in air a /lf 2ch7alqpu. f37qwt 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 scfzb .:ua2r 8 iwt.j-dchool of tuna on a foggy day. Without warning, an engine backfire occurs on another boat 1c-.rdai.ub z2: t8jw f.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 fc p* js .e0fk+d1r8lc pyr0.larom the top of a cliff. The splash it makes when striking the water below is heard 3.5 s later. Ho*cf0d.p .rlescyp lj0a18+rkw 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 (0kb7r cx kog-:sv3u tstone strike the concrete pavement. A moment later two sounds are heard from the impact: 3:sr7gxtc( ouv0kbk -one travels in the air and the other in the concrete, and 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 percent error made over one mile of distance by the “5-seco0f;bx s e0;elvnd rule” for es 0l 0xsevb;ef;timating the distance from a lightning 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 ofp i33z7z; 9izl : ayf4nfsf0yg a sound at the pain 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 leve;byyx9lq5 ; 5qupj(nq6fcbs 3rz r4)zl 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 level of 95 dB when fired simultaneously at3 uz *dwfr4c:n a certain place, what will be the sound level if d3c ur4n f:w*zonly 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 distance from an airplane with four equally nois*cyr+c 0(8y.k et osody jet engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person experience if the capta80cdeor c.s oykt+y(*in 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-no:x3lhzfd+o4 p ise ratio of 58 dB, whereas for a CD player it is 95 dB. 3o xlz:d+h4pfWhat is the ratio of intensities of the signal and the background noise for 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 from a person speaking iewu 7,irg:,1ens-n hqgn1tc*n normal conversatio1ng, si,*rewg q-cnt n7ue 1h:n. Use Table 12–2. 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 stmy + v -fle17,3xah7/qz)dpi6hizp zarikes an 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 mw96llsyx yy5xe j p2+*ore modest amplifier B is rated at 40 W. (a) Estimate the sound level in decibels you would expect at a point 3.5 my5xlx9ye6*wpj +s l y2 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 me 7fmye;(bl12 dopqv *ag)wuo 5ter registered 130 dB when placed 2.8 m in front of a lwb7d 1a ulo)*;qmv (e2opy5fg oudspeaker 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 detect a d2t. 1oc t)y,omddagj7 vph 49mifference in sound level of 2.0 dB. What is the ratio of the amplitudes of two sounds whose levels differ by this amount? [Hint: See Section 11–9.j9t aoyv 7god.42mtm dph )c1,]   

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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 lsnat( ax*(u6 tripled, (a) by what factor will the intensity ax*(6( ltasu nincrease? 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, but one has twice the f;zn gc,gq y).urequency of the other. What is the ratio of)qyg g, uzc.n; 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 level (in dB) of a sound wave in air that corresponds g8 r+tx mg6+nhto amhrnxt+ 8g +6g displacement 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 tone thatfg 8)mx)tif8m has axm it)fmf8)8g 50-dB sound level? (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 highest frequencies that an ear can detect when the som 9;r d)la4ua 667pvwf l8, requ2znklund level is 3la8 7fp u ;nrmlrdazv62q 6 k)4ue,wl90 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 accommodatlx /kys0d ths i2hfg5j *0e14oe a huge range of sound levels. What is the ratio of highest to lx 2 1je hldthgf*ski0o/5 y04sowest 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. j8v y/mpw5p1 ;wp 58cfv(kn5dsyxu8sThe length of the vibrating p;/ v5y5( 8ykn wxc pp8m5uj p81wdsvfsortion is 32 cm, and it has a mass of 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 fum*l:zz, z,agol2o(o; gkpjxwh3 4z 6andamental and first three audible overtones ifh z,o*3 o2w;gxlml4a pz6zj ,zakg:o ( 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 frequency would you expect fw bvs2u/n* kc s:b7.iaq s07qwrom blowing across the top of an empty soda bottle that is 18 cm deep, if you assumed it was a close7iv n* kbc072 :ssqa/wsq wbu.d 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-b:u82s*,ntpggmhl*(vu)y zqb -as 5v tube pipes spanning the range of human hearing (20 Hz to 20 kHz), what would be the rangn zgq b5(8)vs *yu2haumpsv*:t, b-g le 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 freque70vd 8lyok2 )p;dc zct6r d;oancy of 540 Hz as its third harmonic. What will be its fundamental frequency if it is fingered at a length of only d;kvldtazy ;o0)p 26c or87dc60% 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 i3ig f r4k2h3mhs 0.73 m long and is tuned to play E above middle C (330 fhkrh2gm34i3 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 t)2uodn)*4b bbayyx.4 ff ixqvt-7;f uhat emits middle C (262 Hz) when the temperature - b4ti)vy;f24y x7.b)ubadfqxun * fo 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 2x /v5d7qdg ek;0 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 12–1d x d l6ld0y2l;xs10yo0 should the hole be that must be uncovl0 2sxyo 0x1;6 ddldylered to play D above middle 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, ce0*ocpd2mj/di(o/ti6 ( z eqand 616 Hz, but not at any other frequencies inoqi * e m/e 6p(idcdtjo/c2(0z 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 resonates3f9 g;wvcybr,(yst. /b+lq zw at two successive harmonics of frequencies 275 Hz and 330 Hz. What by(9s,rv;f+z ty. /w 3lcqgb wis
(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 waq0cgr :cz)2 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-long organ.,z:eixu7n)j en:nho pi.uh:),z ix: n7nj eonepe 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 outside and 9b2ltc:c0-ut a4mjkuq .d3 hsis closed at the other end by the eardrum. Estimate the frequencies (in the audible range) of the standing waves in the ear ca :02.uclk jus3q4ach9 dmtt -bnal. 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 z w6oar :*dt:uwr*i to adjust two strings, one of which is sounding 440 Hz. Hoz: wi*u r a*r6who:dt,w 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 frequency if middle C (262 Hz (o;2 cqcqj3wm(5zzxo x8 dfp6) 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) operatvwc xs:4.+xq2r *ihcfes 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 played ws.:x2 f 4h*rcvcxqi+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-.(nhv6 *nv p bd1lll(b* 4zuvmHz tuning fork and 9 be ll.v*nzlu6bhb 4d*nv1m ((pvats/s when sounded with a 355-Hz tuning fork. 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 tuned to the same frequency, 294 Hz. The te1c):y ypj tften5 jq,ca9d)0r nsion in one string is then decreased by 2.0%. Wht) yc 5yj1da,jrnc:t e9fpq )0at will be the 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 flutes each try to plwyh -oag f0tmf.x;;: cq2o3vxay middle C (262 Hz), but one is at -g23 ofoq0x.vaym ch; ftxw ;: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, As-apds7sb j )/j+zt0 f, 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 the0daps)tsz/ fb +s -jj7 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 apx.lu3 l16oz; 42l z(fyzwu wfk0cm 6qdart. A person stands 3.00 m from one speaker and 3.50 qw3zu 1;o6 4(ml2dclzf 6.flu 0xywzkm 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 supyjolp287p+ied 71u*spx- b jyposed to be vibrating at 132 Hz, but a piano tuner hears three beats every 2.0 s when they are played together. (a) If one is vibratingl 82e7+xspdjj1ipu*p-yy7 ob 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 w*4+9u :kzx6z xk2id,v ru5lkenxc ed7,dyp1m and 2.76 m in air. How many beats per second will be heard? (Assume T u52udw7kxr vzk xey:lnd,i4d6,9z + *epcxk1 = 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 sirz;6b uixp .l6 lqral92en is 1550 Hz when at rest. What frequency do you detect if you move with a p.2; a ulb9 llzi6xq6rspeed 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 do you detect if a fire engi-(zp ,*1tym+pz*y0nmlddjn o ne whose siren emits at 1550 Hz movestm o1zp dnn(0dm+*-zl,jy*py 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 :0 mcvis fhjkqk 3z845 *ikqq92000-Hz source is moving toward you at 15 m/s versus you moving toward it at 15 m/s Are the two frequencies exactly the same? Are they cloq q0ik9zvqc5ik s*3h8 fj4m:k se? 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 sam;gn7djx9ee5 e+u:me4tz -dmfe single frequency horn. When one is at rest and the t;f5:ee e79meu+dm 4xdzngj- 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? 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 x,e xqsk(z;5j man.+lultrasonic sound waves at 50.0 kHz and receives them returned from an object moving directly away from it at 25 m/s What is the received sound freque, (msk+qx la n5zje;.xncy?    ×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 1sl i*yqq3q4 c r -t+psmup59cat 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 hear iqycp 5 3ls1m*s49 -+picuq tqrn 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 w-yhm7xg ykr(); 9) 5hcxncvxexperiments, a tuba was played on a moving flat train car at a frequency of 75 Hz, and a second identical tubahyx( 75 ;yvxgmxhw n-9 k)c)cr 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 ultrasound w h5bal7;jc/j*xo ztbfrq/- p7aves to measure blood-flow speeds. Suppose the device emits sound at 3.5 MHz, and the sp- rjtafzb/7 ;7qh *c 5l/jpoxbeed 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 ulhl-rinl 4 d.5btrasonic waves 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 emits2 t5:d + g4z2pnkdwtkb sound of frequency 570 Hz. When the wind velocity is 12 m/s from the north, what frequency will observer:dbg4+dpk 5wttkz 2n2s 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 o7)u s2.ff4ko(zkxa0l*sq bs 7cp bse9n 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 th/1d.)9iat kquqx: eele speed of sound is 310 m/s (a) What is the angle the shoc1eqxk9u ltd/:a iq.e )k wave makes with the 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 9(hiif,mg38eg 1/xfyi xgm) f thin atmosphere of a planet where the speed of sound is only a1 fiy(g8 ) g/xfimmx f3ehg,9ibout 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 wq9q -jq 7 mya+0emivk1ave angle it9jqmk0 7e q-qiv+ym1a 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 gu hlsp/awv ;zrcwo8 v c0(11i/jr6h//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 sebz3b ) p cr;7p :xxv/*eikj9y bjh*8ede a plane exactly 1.5 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 distance of:jk;xd/3e9 8x b ij)*phcv p7zey*rbb 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 j-jx lkg h 86l1;4xqwzpulses downward from the bottom of the boat, and thx 8w1l k-j q4jgl;6zxhen 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 th.la d.u .7nq rjo.70kkp*pshuere 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 disqdm-c i8v),s. g kf1erplay called a sewer pipe symphony. It consists of many plastic pipes s)mvgqif,r .kd1 8-ec 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 a person makes a sound close to the threshoi 62tv rzw*gn;ld of human hearing (0 dB). What will be the sound level of 1000 such mosqugv6z; w nit2r*itoes?    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 whewv k9 8:stobn5f 3dhc5n an 82-dB sound and an 87-dB sound are heard simultaneously?9 nvd5sbf t3wkc5:8ho    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 from a louds x-g0 fa3efa;irm ,s)hvrf 8y8peaker, placed in the open, is 105 dB. What is the acoustic power output (W) of the speaker, assuming it radia)fig r,r8a 8hae-y;sxf0 vfm3tes 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 lsqrpx9wn) lxrw9 .0i tebs)+p:cdhk q;5+w:W output at 1000 Hz. The power output drops by 10 dB at 15 kHz. What is the power x)pr:l b5kn9;whq0w .w )rqp +sdsitc+x 9:le 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 typi+:+zgzak*ncdl/b 9nlq;te g0n e,tq6 cally 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 the average human ear has an effective radius of 2.0 cm. What would be the power interceptbtn:,e;kldegz9 6q+nn 0t/lcqz*+ ag ed 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, the ga )z0zz ,doiz+y3)lllm4 og+h jin, 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 frequencyfj wwnaj91- ., idwz3v 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 0zgofus ,a(aweh88 d +a fundamental frequency of 4400u88a afh( z +eg,swdo Hz and a mass per 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 tube f w x -af(nj6r.ce2rfq/illed 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 theaxe.(rc2rfj/n fw6q- 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 thq q5/( bd t.op,2kvq(wgkvsx9at is open at one end and also 75 cm long. How mbqtkv(2x/ g.qds 9pwk5o(, vq uch tension should be 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 lpl f(r84 zh w -ba.*+esq:haryoop (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 two sources. Thuh*xhoa as/)vwx 2.s9u3c d,g+ (fbl we 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 fromhw* 2x )+os.d3uwf slh,bx9gauv c(/a 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. Th ss+)s 5whqaq7e conductor on the stationary train hears a 3.0-Hz beat frequency when the other train approaches. What is the speed of the mw +h5qa qs7)ssoving 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)9 y1r* thtvh x-mvhjkr27p g, it approaches you is 538 Hz. After it passes you, its frequency is measured as 486 Hz. How fast was the train movingkxrt-mh1 2,v)hv9*ptjgyh7r (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 theof 2 u:re:k:l v35igdk 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 by on the strg2vud35 l ekkrf :i:o:aightaway. 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, produ27q zjh9v- ulsce a beat frequency of 11 Hz. The shorter one is 2.40 7qzhu 2 l-vjs9m 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 past a s p 8py/md7kpb: -8eqrotationary 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 after they have passed him, at rp 8/emy7-8b :kdqpo pC?
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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 il rf0ht l +5ccynl o-v,g52rw1n the aorta is normally about 0.32 m/s what beat frequency would 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 hll-t5c25 f lc0r w+ygr v,o1n1.54×103 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 whi we)h1d1)uz rule the moth is flying toward the bat at speed 5 m/s Theeu u11d whr)z) 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 pulses as it approaches *a3o-qk0 uf,d ylzc1cn7:uxg a moth. The pulses are approximately 70.0 ms apart, and each is about 3.0 ms long. How far away can the moth0*-:accgo dn uy3luzk7 fq1x, 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 t2jbr bqhp08li- mb 4:dd:hfl 2o send signals from one Alpine village to another. Since lower frequency sounds are less susceptible to intensityjfm:2 2h-bpl8hlb rq4dib:0 d 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.) 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 b 2 2bm02 5lztu*ovy8fgg2avg ae compromised by the presence of standing waves, which c 2tgz2mlagabg2028f o5*uvvy an 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, ctyz.7dus6r ao1nq k,2 alled “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. W q 2. 7tu,oskryan1d6zith 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 thresh fh-qaim 0ly5, cl*,hgold of hearing for the human ear at a frequency of about 1000 yi5*hcglqfm la ,,h0-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 the ground hears fpwv 8l(:n ggr-.km4w4e wf 9lthe sonic boom 1.5 min after the l. (kpwlv8:ew9 -mwnf gr 4gf4plane 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 speedboat il(lgzh0 egae)0li m5 ,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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