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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 a cd3us v)( jrnk(:s;fbwave?
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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 oft2*k jk*gi *ap30c iil 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”k 5ze. dur 1oukg(a4r9 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 be heard at the other cup (Fig. 12–29). Explain clearly how the sound wave travels from one cupuue9(dz4 r 1.rg5ka ok 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 wate2eog z35v:m bsl33s64vgd ufir, do you expect the frequency or wavelength to changbg4i33 5mo3d2v6 ul sezfvg:se?
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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 thad28 .vkovp3eo n:eze *t the speed of sound in air does not depend significantly ozo* 2 38vn:.ev pokdeen 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-pitcmsrbc0pqbz57b21 zh bj*q3 +8lca/am hed. 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 temm8 q/koxg)m1rperature 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 amplit n8mhn(ymyop0(7 *v snude of sounds in various frequency ranges. (An example is a car mufflevm7ysm0(n *nyopnh8(r.)
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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/,a 0oq2qgi n*pycedf.r a9w2 guitar (Fig. 12–30) spaced closer together as you move up the fingerboard towarogce.,2np /*290a yiaqqrwdf d 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 bu)xucsu 8wd+q)y fu ot1k: 7r7uilding. 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-frequen7 u)udf+ 71:ycuw)8xourqsk tcy 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 vb 3q,+8dj bxh,,evubuag+u2be due to “interference in space,” whereas beats can be said to be due to “interference in time.” Expl,uubxjhegqb +3u b,+adv2 ,v8ain.
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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 speq0)38ck(qeo bhntf +qakers were lowered, would the points D and tqqk3ch)e f8qb0+ (no C (where destructive 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 protecting ty3auk- bk*wki.c)ku 7 0y*wn:tc:f wxhe hearing of people who work in areas with very high noise levels have consisted mainly of effory0 :y:3 *akx unuw f)k-cwwkbt*c k7.its 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 shown in Fig. 12–31. Each wave can b r jfp4vjvx:xp) o.k./e thought of as a superposition of two sound waves with slightly differeokfv4).. : x/pj prjxvnt frequencies, 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 obseoy:+2 q pwqmt906 tmvqrver move in the same direction, with the same velocity? Ex vtq6q2tq+9p0:mywm o plain.
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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, cn mmq,3 r q81o)*izrjwill this alter the frequency of the sound heard by a person at resq 3 r r*qzjc81,m)oimnt 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,e:e5v ac/esm9 gn1 .5wjd rgw positions 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 9r5ewwcv5 ,a . 1mdsge/gn ej: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 listeni:zcwtl99is 2yng for the echo of her shout reflected by a cliff aizt9 2c9syl:wt the far end of the lake. She hears the echo 2.0 s after shouting. Estimate the length of the lake.    ×102m

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19#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A sailor strikes the side of his ship just below the waterline. He .gw 3au6qs6rn-0zvt*bk 2ctj hears the 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 sekz6vs.23 jq*0rtbtg anw c u6-awater 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 at 2p oxmrx;4 :ty 4*dv-cd0 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 8 zl-v+yzik5p kp.e/z-u*msejust above a school 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 backfir- s8*luykpp +vk .iez5mez/z -e is heard (a) by the fish,    s (b) by the fishermen?    s


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22#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A stone is dropped from the top of a cliff. The splash it makes when du7 ukg.up/is( p9pf1 striking the water below is heard 3.5 s later. Howsp7u( gfdk/1 .9 piupu 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 hu6h o/bsi,o+ue/;sos*qx +lv mge stone strike the concrete pavement. A moment later two sounds are heard f;+/ix m+/q*sohlosbvue,6 sorom the impact: 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 .teyan;7tt +cdv / -jad/ etf7“5-second rule” for estinctf7 vt;a-e 7e /tj.tadd/y +mating 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 of a sound at the pain level of 12h- s 6ai6lc/cdlb2nf t.*r3su 0 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 whoylaz7ea/x3 4xt 3 q 0uf,/srjuse 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 dBu+j 9)nfxrqi 1 when fired simultaneously at a certain place, what will be the sound level if only one iu+q1 x j)in9frs 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 equal;q(6 hq13 c;iwap3z*p f bwngily noisy jet engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person experience if the captai wqngc6aiz ib(1;hp;w33* pqfn 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-noisphm;v z6bh 7-(gbtev.e ratio of 58 dB, whereas for a CD player it is 95 dB.hz(.7 g v-;b6vehmpbt What 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 w;wpue cv +82z(v e3rbperson speaking in normal conversation. Use Table 12–2. Assume the sound spreads roughly unifozwvrewc 3u;+b( 8p2 vermly 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 strirjp 2/ b m*gssc+-vo0 u*lmn+okes 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, wi /ut(r7bk0b9zuhr2ehile the more modest amplifier B is rated at 40 W. (a) Estimate the sound level in decibels you would expect b /ut9i r z(ebhkur207at a point 3.5 m from a loudspeaker connected in turn to each amp.I250 =    dB I40 =    dB (b) Will the expensive amp sound twice as loud as the cheaper one?

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33#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  At a rock concert, a dB meter registered 130 dB when placed 2.8 m in fjz e .)b-f.5iqtsl. rlront of a loudspeaker on )-.j5eq.t.lsli rb fzthe 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 difference in soez+/ fx4hph +dsbt)p: und level of 2.0 dB. What is the ratio of the amplitudes of two sounds epds 4+z :xtf +bhh/p)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 a sound wave is tripled, (a) by what fact wup.7/) 7(bykbnwg hmny7 lo-or will the intensity inc k7-gbn/7wpny7.) (wblyum ho rease? 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 q-blr+0 . o5hlpq/+hqrnay4 wg mf7 .iy mq;t,amplitudes, but one has twice the frequency of the+4aor 5 . wb fhq7qiy+qtmqnpmylgh;0 l/ .-,r other. What is the ratio of their intensities?   

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37#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What would be the sound level (in dB) of a sound wavexo8os )yau*8 l in air that corresponds to al 8*o)axyo 8us 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 hav:b;twk 7 f)gj ma3htthfj(09fe what sound level to seem as loud as a 100-Hz tone that has at f (b9th;mkafh g)f:07tjj w3 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 del7yp6 2c8zmmqa+ zij (tect when the sound level is 30 dB? (See Fig. 12–aq y6mic2pz+z8 (7 mjl6.)

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40#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Your auditory system can accommodate a huge range of sound levels. What is the 9uraq)z :nd l)ratio of da9rz)ulq:n )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/,i- 27esq l2j:rsj trf8ko-bl8 nbdk frequency of 440 Hz. The length of the vibje7l-nr ik/2s l-8bks2obt f8 ,jrqd: rating portion 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 long1scsqg km xm2e(( xc3-. What are the fundamental and first three audible overt-( qes xkc(1 smm2xgc3ones if the pipe is
(a) closed at one end, f1 =    Hz f3 =    Hz f5 =    Hz f7 =    Hz
(b) open at both ends?f1 =    Hz f2 =    Hz f3 =    Hz f4 =    Hz

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43#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) What resonant frequency would you expect from blowing across the top of an ebqo e :ixnifax7-5) .suca4;ympty soda boa 7xiybnqo -cu.;)x5:ief4 sa ttle that is 18 cm deep, if you assumed it was a closed tube?    Hz (b) How would that change if it was one-third full of soda?   Hz

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44#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If you were to build a pipe organ with open-tuf4lg12s)u w dbbe pipes spanning the range of human hearing (20 Hz to 20 kHz), what would u bdl 4)sfwg21be 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 of 540 Hz as its third harmonic. 8z nivpbzx-dq 49zt0-3 pk )hdWhat will be its fundamental frequency if it is fingered at a length of only 60% of i94z) znvi bq3-p-kxtpzdd80h ts 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 E abkzooy,bc * /5i cvijyb: 457wdove middle C (330 Hzwo v*:4 z7oci55j/dbky,y bic ).
(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 that emits middle:gaplt(bmkuovw 5u;j : 4-pt wn,+d c5 C (262 Hz) when the temperature is 21 k4pu-5v(g cd,b+tjp:5 w;mlo twn: ua 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 p8)x69 b(skn b7o8 ga* tzxlf:/s2-bft lyal e20 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 1m. 7f59s fnqy1 pns5m99wq auupcdq4/2–10 should the hole be that must be uncovered to play D abpfmsyaq7591qusm u fcq94nnd/ 5w.p9 ove 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 awhrud 7mih14y q,j(-xt 264 Hz, 440 Hz, and 616 Hz, but not at any othexqjihwhy47d( ur, 1-m r frequencies in between. (a) Show why this is an open or a closed pipe.   (b) What is the fundamental frequency of this pipe?   Hz

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52#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A uniform narrow tube 1.80 m long is open at both ends. It resonates atf 2;e ftbsy)qim;x,d( two successive harmonics of frequenct2fxbqm)f;;,e( d i syies 275 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 /rzg/c etv up+kkq7*, 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 audiblep8oh1) 5aqv 3ztq,krlt uja) 6 range for a 2.14-m-long organ otuq6z5q1t8l)v a hk ,3)arjp pipe 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 approximdgik +y9 +jno(t2 9jr7egon3oately 2.5 cm long. It is open to the outside and is closed at the other end by the eardrum. Est3+je2 rigk njtoy79d 9 n+(oogimate 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 :4epzo9afxs8 :uli zl 0ob b.*s when trying to adjust two strings, one of which is sounding 440 Hz. How far off in frequencypol :oxzs *bu .izf bl80e94a: 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 ifqt*g7t i5+zc8x1w gwd 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 whistlei,acp-5atvl y2u/ xoe;t b, .t operates at 23.5 kHz, while another (brand X) operates at an unknown frequencytv o; / cbauttpa52ie,xy-, .l. If neither whistle can be heard by humans when played separately, but a shrill 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 when sounded with a 350-Hz tuning fork and 9uhifvujl j-fk ;-*s:i7h* 1 nv beats/s when sounded with a 355-Hz tuning fork. What is the vibrational frequency of the string? Explain your re*kjjf-s*:if-7 v1hlvuh nu;iasoning.    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 4)u aoziq 0e0eto the same frequency, 294 Hz. The tension in one string is thez4q euao)0i0e n decreased by 2.0%. What 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 play middle C ( k.z ik1b8x,onh8 rxu)262 Hz), but one isbu,zrh. 1i8 xxk n)8ok at 5.0°C and the other at 25.0 C?    beats/sec

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62#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You have three tuning forks, A, B, and C. Fork B has a frequencytif ; )a*.,g keeqz6ed of 441 Hz; when A and B are sounded together, a beat frequency of 3 Hz is heard. When B and C are sounded togqae;e .e*)kdztf, 6i gether, the beat frequency is 4 Hz. What are the possible frequencies of A and C? What beat frequencies are possible when A and C are sounded together?fA =    Hz or    Hz
fC =    Hz or    Hz
|fA-fC|    Hz or    Hz

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63#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two loudspeakers are 1.80 m apart. e fme3w.ma f6u/;kly2r+kp3p A person stands 3.00 m from one speaker and 3.50 m from mp3 .emaue;wk/pf2 6r yl3+fk 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 vibr,uficj wfj at,b9 rh v2702v4mating at 132 Hz, but a piano tuner hears three beats every 2.0 s when they are played together. (a) If one is vibrh vta j4u cf,jf2b7r0w29iv,mating 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 mzq(sj0le1;w j in air. How many beats per second will be h1je(0zl; jws qeard? (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 siren is 155slpi9 pfz6g: :0 Hz when at rest. What frequency do yol96pif:pgs :zu 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 stilld( 0iyl slf1x:. What frequency do you detect if a fire engine whose siren emits at 15l yxlsdf:0(i 150 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 vmnceb:6g78w6c j h r3a 2000-Hz source is moving toward you at 15 m/s versus you moving toward it at 15 m/s Are the two frequencies exactly the7j38 cv6g c:6mn bewhr 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 siny2jy ) wex ) ijo18bxp2hkjv.pl6u-g3gle 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 beat frequency of 5.5 Hz. W.l kpbpoyehx6 yjg w)i- 2vxjju832 )1hat 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 wc/4u nzl -kwboy+b pew8 435jwaves 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 frequencjo4/bn w4 5 8ze+bly -wkwu3pcy?    ×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 wallxwamo-,1 a4wb at a speed of 5 m/s As it flies, the bat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency does the bat hear in the reflected wava1bx4aw o-wm, e?    ×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,k xialu+ ax *7o/uzp1) 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 was heard if the train car approached the stationxi *paozax /l) 1k7uu+ 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 ultrasoun ig0uhs;2fwxi62nv 3gd waves to measure blood-flow speeds. Suppose thiv uf3w02h s;x26ignge 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 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 ultrasoxfn6h62z y )uknic 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 emits soundvt;afb1u01q l of frequency 570 Hz. When the wind velocity is 12 m/s from the north a1;f btu1l0qv, what frequency will observers hear who are located, at rest,
(a) due north,   Hz
(b) due south,   Hz
(c) due east,    Hz
(d) due west, of the whistle? What frequency is heard by a cyclist heading    Hz
(e) north    Hz
(f) west, toward the whistle at 15 m/s?   Hz
Assume T = 20 C

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76#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How fast is an object moving on land if its speedyy:1h tsrbk0 f jga. h00,(6:plr lgii 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) pajcsv3:x 4payl dr* y4awpiow p9/5//6emr 2What is the angle the shock wave makes a*y/vcpr 4wae64r:5/a p2i9l j mo/ wp3y sxpdwith 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 thin atmosphere of a planet where t ubbkorf)i;-kfzx2ui d4 7 hw16l gi9,he speed of sound is o-f h2w izrk ;giudx64il)o k19bbuf,7nly about 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. 8mtmc o x j8f18a5j ;rzo0ho zymzc*1*Determine the shock wave angle it promjto1rmoyc88 fz oh c ;**ax 05jz18mzduces
(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 9xor v0wh*/ z4:phkky /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 overho86: ccu 8xi ,gyv(pa1gsfm)c ead 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 boom, thecf gv)1 oxga(, 886muiy :spcc 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- qk8w*2nnm dddj7 xwkpj, ;n;-Hz sound pulses downward from the bottom of the boat, and then detects echoes. If the maximum depth for which it is designed to work is 200,7p*x 8w2kddj- ;qwnk;d jnnm m, what is the minimum time between pulses (in fresh water)?    s

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83#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Approximately how many octaves are there in the human audible ra-z t vndq;*b9omkji.f+ + lyz(nge?    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 za59 ovlnb7;k sewer pipe symphony. It consists of manynbv9l ka75 zo; plastic pipes of various lengths, which are open on both ends.
(a) If the pipes have lengths of 3.0 m, 2.5 m, 2.0 m, 1.5 m and 1.0 m, what frequencies will be heard by a visitor’s ear placed near the ends of the pipes?
f3.0 =    Hz
f2.5 =    Hz
f2.0 =    Hz
f1.5    Hz (Round to the nearest integer)
f1.0    Hz (Round to the nearest integer)
(b) Why does this display work better on a noisy day than on a quiet day?

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85#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A single mosquito 5.0 m from a persoz,5 wzlayk ( cknvr/2;n makes a sound close to the threshold of human hearing (0 dB). What will be the sound level of 1000 suchac5 z /;ywlk nr2,vk(z 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 n oeda7d hc--*sound level when an 82-dB sound and an 87-dB sound are heard simultan n7a*o --dechdeously?    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 lou 28ym py4rop2kdspeaker, placed in the open, is 105 dB. What is the acoustic pk2 p2om4yrp y8ower output (W) of the speaker, assuming it radiates equally in all directions?    W

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88#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A stereo amplifier is rated at 150 W output at 1000 Hz. The pow(2aq5tk m/ hdwer output drops by 10 dB athmqa(k 5d t2w/ 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 devi 7(yxw,+ tgvqcces over their ears. Assume that the sound level,t cvyx7q( +gw 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 intercepted by an unprotected ear at a distance of 30 m from a jet airplane engine?    W

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90#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  In audio and communications systems, the ga3k. (mm3;x0rhp cfn zmin, 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 frequen8a 9tsms2v)+us ;5up;ar kpi,luh sq.cy 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 ayro9a0q vi5 mx,p0w*nj2f3 tk fundamental frnr0 ,5v9wftay*xp2oim 3kqj0 equency of 440 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 filled with wa mwlljkodlo: ) /.4ke3ter (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 waterje /ll.dl:)oo m4kkw3 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.l6 w4bcuuwh 7im/y 5+e10 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 third harmonihub+7 /i5wel 4cuwm6 yc 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 on46 gl /x66gkko; lgtsh,w1vsfe 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 500–1004)rgxr38prv )ukh9 t b0-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 souhkgr))3brv4t p9r 8uxnd 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 trainvp)xwpufdkq( x in uv8 0,/z(: is stationary. The conductor on the stationary train hears ,v0)/i : npw((q xzfkuvp8duxa 3.0-Hz beat frequency when the other train approaches. What is the speed of the moving train?   m/s

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98#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The frequency of a steam train hxq f+3km n-tb+-i dp)my+f k0whistle as it approaches you is 538 Hz. After it passes you, its frequency is measured as 486 Hz. How fast was tf dy qb -)mik0n3-hmtpf+xk++he train moving (assume constant velocity)?    m/s

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99#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  At a race track, you can estimate the speed of cars just by list(ftgso d*2wikwj,5bsr83fw : ening 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 by on the straightaway. How fast is it gk g:f*s 5 bd,8owfwt (js32rwioing?    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, proh+:gc,s yzt fizd) 10dduce a beat frequency of 11 Hz. The shorter one is 2.40 m long. How long is the othhyf)c:i0z +dg1 , sztder?    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 op+;k u si,a-vrrposite 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, ;+,-asu krivr 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 blyb*at-eewi5 tci,g:ff6 y a ihdr3q pi21i 27.ood flow in 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? Assumeefr f76 bp3w1i* a: i-,th2yi2ec gii5ydaq .t that the waves travel with a speed of 1.54×103 m/s   ×103Hz

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103#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bat flies toward a moth at speed 6.5 m/s while the moth is flying toward thd vdfop8yd09 ucvx8( 4si l2l3e bat at speed 5 m/s The bat emits a sound wave of 51.35 kHz. 8fiup(9d c3dxdys vl408lo2vWhat 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 a motu04 j0-levj (ebj+ xlch. The pulses are approximately 70.0 ms apart, and each is about 3.0 ms long. How far away can the +cu v4e0jlj-b0exjl( 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 2qjim*i gv02 hused to send signals from one Alpine village to another. Since lower qm0* vgi22jihfrequency 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.) Model as an open tube.
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106#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Room acoustics for stereo listening can be compromised by the presence of stand +spd89 -d uobe*snf-jing 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 fd- sb9djoue 8n+ fp-*srequencies 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 demonstrat ,)t+ilc-6gmnbanty fh86 pb2 ion, called “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 +8t)yb ,gnmha-6b ti6np 2flc 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 frequkz+f;n7ih/ ts 3yru 2fency of about 1000 Hz iit s/hk+2 rf3unfz y7;s 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 the sond6x2 r *xfau(g0n3lgakf ic(l 5 yj4*dic boom 1.5 min after the plane passes directly overhead. What y4dx cdl(20xfak*g 6i*rl(na guj 53fis 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 iq cjlb2p l2vp5w5 25iis 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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