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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: 游客未登录  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 thaz x7vol/vpzi:5d 0hv (t sound travels as a wave?
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2#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
What is the evidence that sound is a forx 8 u i08xeaativrz 206*axd8km 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 “telepho 8)s65yfc2t q5x sp vdnn g)*fgsx*m1pne” by attaching a string to the bottoms of two5s)tcs)gpvg nm*s6 qpxx25 ydn f* 81f 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 cup to the other.
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4#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
When a sound wave passes from air into water, do you expect the frequlfo r)y/k9;edency or wavelength to chane /;9fdk ly)orge?
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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 thata yv zb5:ea(/gv)o*w y7 t 2hsui*rr9n the speed of sound in air does not depend significantly on frequencuszr/e)gnobh2(v iy *97a5rt:y*a wvy?
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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 hastxzx )lqjn o33ler6nx5 6m s1fge k023 inhaled helium sounds very high-pitched. Why?
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7#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
How will the air temperature in a room ao(la.4f skq3affect 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 nh- f.em8vw r+be used as a filter to reduce the amplitude of sounds in various frequency ranges. (An exa. n-vrem+hf8wmple 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 togeth ,8zmdv r ;xffpep8g95/dx ec8er as you move up the fingerboard toward the bridge?gr;8d /z9,f8v8em xcex pfdp5

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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 q.:bt- : rqn5bda /huqbehind a building. Initially you hear it but cannot see it. When it emerges and you do see it, its soun.5- rhd qbq:/:nuaqbtd is suddenly “brighter” — you hear more of the high-frequency noise. Explain. [Hint: See Section 11–15 on diffraction.]
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11#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Standing waves can be said to be due to “interference in space,” w4)psaz0i lhn (hereas beats can be pn)a z0(ilsh 4said to be due to “interference in time.” Explain.
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12#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
In Fig. 12–16, if the frequency of the speakers were lowered, would 7vsd ga+q03hythe points D and C (where destructd+ avgs3h y0q7ive 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 the hearing of people who work in arec1nzwf6x s2kb+3 gn;n,,ey vlas with very high noise levels have consisted mainly of efforts to block or reduce noise levels. With a relatively new technology, headphones are worn that do not block the ambient noise. Instead, a device is used which detects the noise, inverts izvn21g;cnny6+kwe3, xs,fbl t 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 be thought of as a supczb6v vph c kj*ms8+)(erposition of t6v(jvc) 8c*m bpshk+zwo sound waves with slightly different 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 i4fzqfb0z bn50w r:t ib gri0016u+ixthe source and observer move in the same direction, with the sai4ux bgzi5r rt0bn6fb f: 0wi001izq+me velocity? 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 alter the fs. 5x8eqxjupau 3 u(e0requency of the sound heard by a person at rest with respect to the source? Is the wavelength or velocity changa8eu(5p .u3eq 0su xxjed?
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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 chz:x zv0n, h-kii 3os:hild 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, zk :inx:io0s 3hzh ,v-will the child hear the highest frequency for the sound of the whistle? Explain your reasoning.

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18#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A hiker determines thex+c 8fowq2 bx) length of a lake by listening for the echo of her shout reflected by a cliff at t wxofc2+xqb) 8he far end of the lake. She hears the echo 2.0 s after shouting. Estimate the length of the lake. $\approx$    $ \times10^{ 2}$m

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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 thc9 0jttpscv4 l4y0)hbe echo of the sound reflected from the ocean flooch 90v)04t ytbcj4s lpr directly below 2.5 s later. How deep is the ocean at this point? Assume the speed of sound in seawater is 1560 m/s (Table 12–1) and does not vary significantly with depth.    $ \times10^{ 3}$m

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20#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Calculate the wavelengtb-6 uvoh8ayg( hs in air at 20 $^{\circ} $ C for sounds in the maximum range of human hearing, 20 Hz to 20,000 Hz. $\lambda_{20Hz}$ =    m $\lambda_{20kHz}$ =    $ \times10^{-2 }$ m(b) What is the wavelength of a 10-MHz ultrasonic wave?    $ \times10^{ -5}$m

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21#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An ocean fishing boat is drifting just above a school of tuna owgv 1ae *s;9 yaegqtqd8z4w1/ n a foggy day. Without warning, an engine backfire occurs on another9y zag18 v1 eate*4sw;q/qg dw boat 1.0 km away (Fig. 12–33). How much time elapses before the backfire is heard (a) by the fish,    s (b) by the fishermen?    s


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22#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A stone is dropped from the top of a cliff. The splash it makes vl 7 pwk0/*p*zmmmoy*u 9mj8. 9 egcoabt):pnwhen striking the water below is heard 3.5 s later. How hitlma*kcnup.v p*oo jyzmb*m w9m7 )9ep08/:ggh 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 hup gixtz0nyrf.bz/-8 ( ge stone strike the concrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other in the concrete, and they are 1.1 s apart. /8i .z0-fbgypz rntx( How far away did the impact occur? See Table 12–1.$\approx$    $ \times10^{2 }$m

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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 dis z)yapknip5fr*:xd o dur9os55 y)n/5tance by the “5-second rule” for esti9 5py ouy5)d:r)nkpz/ no fa*i5xdrs5mating the distance from a lightning strike if the temperature is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

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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 pls06u*ka xnj9 zl9vw; ain level of 120 dB?    W/$m^2$Compare it to that of a whisper at 20 dB.    $ \times10^{-10 }$W/$m^2$

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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 wha;h n2,k+z.jy7fcqyiose intensity is $2 \times10^{ -6}W/m^2$?    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 prvebzirk50r3 6oduce a sound level of 95 dB when fired simultaneously at a certain place, what will be the sound level if only one is exploded? [Hint: Add intensities, no5izkre6v3r0b t 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 :hv2n. -ngr zenoisy 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 buz.ne-v g2rn:ht one engine? [Hint: Add intensities, not dB’s.]    dB

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29#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A cassette player is said to have a signal-to-noise ratio of 58 dB, wp7bprgi :),hvhereas for a CD player it is 95 dB. What is the ratio of intensities of the signal and the background noise for each device? 58 d,:7bv gh)irp pB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

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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 fro. 8;m6 bvvybr( 2lasfjm a person speaking in normal conversation. Use Table 12–2. Assume the sound spreads roughly uniformly over a sphere cen2a8(6vj;vsr.y fl mbb tered on the mouth. $\approx$    $ \times10^{ -6}$W(Round to the nearest integer)
(b) How many people would it take to produce a total sound output of 100 W of ordinary conversation? [Hint: Add intensities, not dB’s.]$\approx$    $ \times10^{7}$people

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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 whose areae1 )-s lzf1hjx;iy2dx5f 860oiy dtrx is $5 \times10^{ -5} m^2$ (a) How much energy is absorbed by the eardrum per second?    $ \times10^{-12}$W (b) At this rate, how long would it take your eardrum to receive a total energy of 1.0 J?   $ \times10^{ 3}$yr

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32#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Expensive amplifier A is rated at 250 W, while the more modest amplifie8. sh9 wu ,*elgsvel 9slv-z+qr B is rated at 40 W. (a) Estimate the sound level in decibels you would expect at a point 3.5 m from a loudspeaker connected in turn to eache 8sg s. zs-,ehl*lwqu 9v+9vl amp.$I_{250}$ =    dB $I_{40}$ =    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 frokgkor/h xoh2 4,s d4j1nt of a soh 4hj2/x d4o,g k1rkloudspeaker 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?$\approx$    $ \times10^{2 }$W(“Round to one decimal place)
(b) How far away would the sound level be a somewhat reasonable 90 dB?   $ \times10^{2}$m

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34#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Human beings can typically detect a difference in sound level of 2.0 dze5b en,s0 (ji6m yjo7*gq uj.B. What is the ratio of the amplitudes of two soundsy5 ijouneqe gj60j(mb*z7. ,s whose levels differ by this amount? [Hint: See Section 11–9.]$\approx$   

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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 r,1pacf/.i+ pn pg2v ov 3po:x6e9tfjwave is tripled, (a) by what factor will the intensity increase? Incref9+6 3x pg /c2.a tpoo:ifp,v1nerv pjase 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 d2 +77 aitx,bsqf8bnexisplacement amplitudes, but one has twice the frequency of the other. What is the ratio of their int 2+b7itsfx 8a qneb7,xensities?   

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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 thaewb yww4c 9 t1ui84l4ut corresponds to a displacement amplitude of vibrating air mol1ult8ewb y4wcuwi 449ecules 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 thhi9 t0b /6yc+.s skdufat has a 50-dB sound leveld ycf90hki/ubs 6+st. ? (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 highy.u0ew c/x z*;yftqxh.jo1 4rest frequencies that an ear can detect when the sound ltf xcu yyqzwj./oh;41.0xre*evel 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 rangeoyqamu9j(k y a*;k 1z;-fxw;e of sound levels. What is the ratio of highest to lowest inte;az;j e*uwk q9yfo-1 a;m(xy knsity at
(a) 100 Hz,$ \times10^{ a }$ a =   
(b) 5000 Hz? $ \times10^{ a }$ 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 frequencyk7o -xl*n 1fjv of 440 Hz. The length of the vibrating portion is 32 cm, and it has a mass of 0.35 g. Under what *x7nf-k ovjl1tension 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 lo/503)z h/ldfk ck+xwidvdyop92 lrcq/nd5v4 ng. What are the fundamental and first three audible overtones ifr vkz2dk y4l3 x0l)ofc+dn5viw/ h9dd c/pq/5 the pipe is
(a) closed at one end, $f_{1}$ =    Hz $f_{3}$ =    Hz $f_{5}$ =    Hz $f_{7}$ =    Hz
(b) open at both ends?$f_{1}$ =    Hz $f_{2}$ =    Hz $f_{3}$ =    Hz $f_{4}$ =    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 a ybvh,( (o6upzs8niu-n empty svoh np8uzu6sb-(y(i ,oda bottle 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-tube pipes spanning the range cih;pehzg5y) 7 o2hy:of human hearing (20 Hz to 20 kHz), what would be the range of the lehh oychez5;p2: giy)7ngths of pipes required? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

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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 hz8 hjtiq :9;zwv (v+xras a frequency of 540 Hz as its third harmonic. What will be its fundamental frequency if it is fingered+j:;qhtvi8zrvw (z x9 at a length of only 60% of its original length?   Hz

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46#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An unfingered guitar string is 0.73 m long an wtmjud9.3e nc17adh 6xa 6;eb3mj2ljd is tuned to play E above middle C (330 ct.7jamd6 632 eh9 mlj;uj3n dwxb1 aeHz).
(a) How far from the end of this string must the finger be placed to play A above middle C (440 Hz)?$\approx$    m
(b) What is the wavelength on the string of this 440-Hz wave? $\approx$    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 leng( bzxy rp:xsq51 ho(.wth of an open organ pipe that emits middle C (262 Hz) when the temperature yw5.:b r sx( pq(h1xzois 21 $^{\circ} $ C.    m
(b) What are the wavelength and frequency of the fundamental standing wave in the tube?    Hz    m
(c) What are $\lambda$ and $f$in 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 2jry / ju797bpc0 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ 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 mouthpieceh3co lte 0+avnh7dv;/ of the flute in Example 12–10 should the hole be that must b +dnova lth ch7v0e3/;e uncovered 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 $^{\circ} $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 616 Hz0b7hg6k: pw ax, but not at any other fr hbkxg706pw:aequencies 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 resona,-;vt e0 zed d69pqngetes at two successiv nev,d; tqpe6e-0 9zgde harmonics of frequencies 275 Hz and 330 Hz. What is
(a) the fundamental frequency,    Hz
(b) the speed of sound in the gas in the tube?$\approx$    $ \times10^{2 }$ 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 or1t 1s 3l/jyvwi/)fg$^{\circ} $ 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 2.14-3( .db2s rhjxma nr*-hm-long organ pipejh2drs*a(. m r3nx-hb at 20 $^{\circ} $ 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 lonjl .)in 9:ecwog. It is open to the outside and is closed at the other end by the eardrum. Estimate the frequencies (in the audible range) of the standing waves in the ear canal. What is the relationship on:e w. licj9)of your answer to the information in the graph of Fig. 12–6? $f_1$ =    Hz $f_3$ =    Hz $f_5$ =    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 onem/q ,ut2xd(c e7i:qcs beat every 2.0 s when trying to adjust two strings, one of which is so, 7uesxm(t 2q/c:cqdi unding 440 Hz. How 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 mirj o::c8 ohzcc :ra87tddle 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)? $\approx$    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) operates y. uo o)yn h1c,qglbd( ln l+)p0)fd;vat 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 play)y n;od0h.n c+p,g oql 1v(bl f))ydlued 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 tunius v/)s+ d2mbang fork and 9 beats/s whe)b+avd/s2 umsn 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 tensiodl 6 ug uxhh y1-k3)uxw*3*is2g ari5cn in one string is th-l ugk2h 6u3 r*u*a5 cy3hs wi1gxxid)en 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 be7aok ycrf2 2lyj gb336 heard if two identical flutes each try to play middle C (262 Hz), but one is at 5.0°C and the other at 25y c3 2 gf2al3jobryk67.0 $^{\circ} $ C?    beats/sec

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62#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You have three tuning forks, A, B, and C. Fork B has a frequency jp1 jt yobmh);-:woh/ 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 t1tp hjm;):j hwyo /o-bhe possible frequencies of A and C? What beat frequencies are possible when A and C are sounded together?$f_A$ =    Hz or    Hz
$f_C$ =    Hz or    Hz
|$f_A$-$f_C$|    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 5tcdwlu1 am51z;z(f wperson stands 3.00 m from one speaker and 3.50 m from the ocf alz51(t5 wwum;1dz ther.
(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 $^{\circ} $C $\approx$    Hz $\approx$    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 ozv3ls4yy 1g7 132 Hz, but a piano tuner hears three beats every 2.0 s when they are played together. (a) If one is vibrating at 132 Hz, what must be the frequency of the oogl1 4ys3y7zv ther ?   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 2qgq-9vj iy/ j8 cxbg3t(;vt oaw0)u f2.76 m in air. How many beats per -biq3)2w q 8(gtujvtjo fygv0c9;a/x second will be heard? (Assume T = 20 $^{\circ} $C)$\approx$    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 firep;(; 8 wa:;8fhjkwfkz i5dztz engine’s siren is 1550 Hz when at rest. What frequency do you detect if you move withz kit;;zj wp(;f8a5w k8zh:df a speed of 30 m/s
(a) toward the fire engine,    Hz
(b) away from it?   Hz

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67#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You are standing still. What frequency do yovhp 6+;+w/iio b:jj vau detect if a fire engine whose siren emits at jvbw;va6+/:ijoh +pi1550 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 av3c9-fwjfo dx/pj w,fcy8 5-l 2000-Hz source is moving toward you at 15 m/s versus you moving toward it at 15 m/s Are the two frequencies 8l,wow/5f --9j cvjffdcyx 3p exactly the same? Are they close? $f'_{source\,movine}$    Hz
$f'_{observe\,movine}$    Hz
(b) Repeat the calculation for 150 m/s and then again
$f'_{source\,movine}$    $ \times10^{ 3}$Hz
$f'_{observer\,movine}$    $ \times10^{ 3}$Hz
(c) for 300 m/s What can you conclude about the asymmetry of the Doppler formulas?$f'_{source\,movine}$    $ \times10^{ 3}$Hz
$f'_{observer\,movine}$    $ \times10^{ 3}$Hz

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69#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two automobiles are equipped with the same single frequency horn. When one isc( y5h5lbs3 fy at rest and the other is moving toward the fyc3lhby s5(5 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 $^{\circ} $C    Hz

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70#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bat at rest sends out ultrasonic sound waves at 50.0w1(p ewvc g9+ d4) wapx3uxix- kHz and receives them returned from an object moving directly away from it at 25 m/s What is the received sound frequ xp- dpix)wwa v1u3ce4(xw9g+ency?    $ \times10^{ 4}$ 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 q2s6(qn t,ykp + yn38ag2x;u2rosl crof 5 m/s As it flies, the bat emits an ultrasonic srp xkt36 rns;,yo+qau2(scylq 28gn2ound wave with frequency 30.0 kHz. What frequency does the bat hear in the reflected wave?    $ \times10^{4}$ 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, ,vwt 8wva9hw9a tuba was played on a moving flat train car at a frequency of 75 Hz, and a second identical tuba pw,9 9wvtv h8awlayed 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 waves to measure blood-flow speeds. Suppotmv al r*,h3gej/5s t.se 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 frequency if blood is flowing in large leg arteries at 2 cm/s./3g s,v ahjetm *5ltr directly away from the sound source?   Hz

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74#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The Doppler effect using ultrasonic waves of uo(j)p -1bh1wpumz0b frequency $2.25 \times10^{ 6}$Hz 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 $1.54 \times10^{3 }$ 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 sound5o-ivt (m +2eei)4h:lf hvrar of frequency 570 Hz. When the wind velocity is 12 m/s from the norf r4e:hv( )lv2e aitr5o+i -hmth, 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 $^{\circ} $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 speed a(vow/-38h upqf tv af 80fz;jtt 20 $^{\circ} $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 dkh hp(i(gh 7v /kgztj;zl8q u/.n4tcc*;i d1of sound is 310 m/s (a) What is the angl htqzud*cicniv/4(gkp1tlh gd z.hk/j(; ;78e the shock wave makes with the direction of the airplane’s motion?    $^{\circ} $
(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? $\approx$    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 wesgbhl -vd53 (here the speed of sound is onlydhv 5ge3 sbl(- about 35 m/s
(a) What is the probe’s Mach number if its initial speed is 15000 km/h$\approx$    (Round to the nearest integer)
(b) What is the angle of the shock wave relative to the direction of motion?    $^{\circ} $

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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. Deterav 2nt mbcpu7a+q6f 8/mine the shock wave angle it produce+vnc uf 6qm27a bp/a8ts
(a) in the air just before entering the ocean, $\approx$    (Round to the nearest integer)
(b) in the water just after entering.    $^{\circ} $
Assume T = 20 $^{\circ} $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 zf8 :uq. yafie4v 1s)f$/theta$ 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 nfiukwc t.:1 :un0*9)xfdathw 3/x qrkm above the ground flying faster than the speed of9 d:xit)3h.ta*w:u0 rn/f u nkcw 1xqf 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, $\theta$    $^{\circ} $
(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 vp u6;9lez:yl 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 m, what is the m:e6vylpu; z 9linimum 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 rasxm1 *bgh n0x(nge? $\approx$    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 cald s7vvsb65vml1 07t ftled a sewer pipe symphony. It consists of many plastic pipes of various0 t67mv7ts5vld1v fbs 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?
$f_{3.0}$ =    Hz
$f_{2.5}$ =    Hz
$f_{2.0}$ =    Hz
$f_{1.5}$ $\approx$    Hz (Round to the nearest integer)
$f_{1.0}$ $\approx$    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 s9ieq- s i6gor9pyp m(zqg- 79tound close to the threshold of human hearing (0 dB). What will be the soun(-gosrg97 izy6q-9piqmp e t9 d level of 1000 such mosquitoes?    dB

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86#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the resultant sound level when an 82-dB sound and an 87-dB :j. bv3a y, ljyz3nvd4sound are heard simultanv3j,zj3dlyvay . 4n:beously?    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 loudspeaker, placed in the open, is t52pbpxa7jory++ twno 1pj-5105 dB. What is the acoustic power output (W) of the speaker, assuming it radiates equally in all dirertpx+bo1p5 a-nytwp 5 j7 o+j2ctions?    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 a;jmjv iw1-(w mt 150 W output at 1000 Hz. The power output drops by 10 dB at 15 kHz. What is the power output in watts at 15 kHiwj 1- ;vjmw(mz?    dB

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89#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Workers around jet aircraft typically wear protective devices over t/(fx;l3x zkj cheir ears. Assume that the sound level of a jet airplakcz( x/ j3;flxne 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 communic 69vivwnn;u z-ations systems, the gain, $\beta$ in decibels is defined as
$\beta$ = 10log($\frac{P_{out}}{P_{in}}$)
where $P_{in}$ is the power input to the system and $P_{out}$ 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 tpxqhy -c,vb4+ v k+c:do a frequency 1$\frac{1}{2}$ 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?
$f_{A}$ =    $\mu_{A}$
$f_{B}$ =    $\mu_{A}$
$f_{C}$ =    $\mu_{A}$

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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 ug+q/+no2c zgcswr 22cm long between fixed points with a fundamental frequency cz2s o wq2+gng/r+c2uof 440 Hz and a mass per unit length of $6.1 \times10^{-4 }$ kg/m
(a) What are the wave speed and tension in the string?    $ \times10^{2 }$ 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 (jh7 bt.*m zaqa vertical open tube filled with water (Fig. 12–35). The water level is allowed to drop slowly zj(7.m abtq*h. As it does so, the air in the tube above the water level is heard to resonate with the tuning fork when the distance from the tube opening to the water level is 0.125 m and again at 0.395 m. What is the 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.t8 laj ci3n0g:n40 fiy10 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 fundament048 3c0i:n n fagiytjlal mode) with the third harmonic in the tube?    $ \times10^{ 2}$ 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 fully usg6 0*gl yw82t.oig loop ($\frac{1}{2}\lambda$) 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 sourc.tllb4j04otcfo57 c x es. 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 fret oclj t5fc40.7bx 4loquency of the sound?   Hz

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97#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two trains emit 424-Hz whistles. One train is stationary. The q;q/(oqfw q g:conductor on the stationary train hears a 3.0-Hz beat frequency when th;: (fw /oqgqqqe 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 whistee+d(50ve t(k o dh q3lf7lzb/le as it approaches you is 538 Hz. After it passes you, its frequency is measured as 486 Hz. Hb lez3f/+7e o 5dldqtvhe 0((kow 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 c y9 drg+bs-h5jan estimate the speed of cars 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 (frequencysj 5-b+gdr9 hy halved) as it goes by on the straightaway. How fast is it going?    m/s

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100#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two open organ pipes, sounding tosvq/i64;9s /hjgm8 scrxz6yygether, produce a beat frequency of 11 Hz. The shorter onjvm8/y ;z xg69syisq r 64hsc/e is 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 (gc 9wmaqz 0k9of a railroad car as it moves past a stationary observer at 10 m/s as shown in Fig. 12–37. If the speakers have identical sound frequencies of 212 Hz, what is the beat frequ0am(w9qg9 c kzency 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 .zlb5 mfg8n8nthe 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 the8lnbng m.zf5 8 waves travel with a speed of $1.54 \times10^{3 }$ m/s   $ \times10^{3 }$Hz

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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 thgc35o b a86hka xh(y)re moth is flying toward the baag3 ahoc kr6h)5(8b yxt at speed 5 m/s The bat emits a sound wave of 51.35 kHz. What is the frequency of the wave detected by the bat after that wave 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 ay5xn.ugz toqghye8) p y(fcv9:h* 2j7 moth. The pulses are approximately 70.0 ms apart, and each is about 3.0 ms long. How far away can the moth be detected by the bat5 y: 82xpgz.)ehyqvug*y ( hntj9cof7 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. 1xvv ;vlt33q *5qtf wky*f:p i-2–38) was once used to send signals from one Alpine village to another. Since lower frequency sounds are less susceptible to intensity loss, long horns were used to create deep sounds. When played as a musical instrument, the alpenhorn must be blown in such a way that only one of the overtones is resonating. The most popular alpenhorn is about 3.4 m long, and it is called the F sharp (or G flat) horn. What is the fundamental frequency of this horn5vv3xl :*tqfyvf;it q kp3w-*, 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 lf *z,iowz5 oodspc,68istening can be compromised by the presence of standing waves, which can cause acoustic “dead spots” at the locations of the preoz wpz5o6d,c*i f, o8sssure 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, calleup-dj9* (iraxvews-hz .8ve0d “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 wev.9ea jr*sx pvi(-h-80 udz. With a little practice, the rod can be made to “sing,” or emit a clear, loud, ringing sound. For a 90-cm-long rod,
(a) what is the fundamental frequency of the sound?    $ \times10^{ 3}$ Hz
(b) What is its wavelength in the rod,    m
(c) what is the traveling wavelength in air at 20 $^{\circ} $ 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 theuy a:kotx2. o:+gtkwwx/i8e. human ear at a frequency of about 1000 Hz yowkt/ akg:2wu8:i+tx .oe.xis $I_0$ = $1 \times10^{12 } W / m^2$ for which $\beta$ the sound level, is 0 dB. The threshold of pain at the same frequency is about 120 dB, or $I$ = $1 W / m^2$ corresponding to an increase of intensity by a factor of $10^{12}$ By what factor does the displacement amplitude, A, vary? 10$^{a}$ 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 z+b.od* i5wit5x aub9 hears the sonic boom 1.5 min after the plane passes directly overhead. What is the plane’s altitude? ax+wu9dtz .i ob55bi*    $ \times10^{4 }$ 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 is 15vkrgm.iw 2+.t)lb f0m $^{\circ} $ 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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