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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 wavw.g k(rd2cne,bovl.mv *sq n4v, ;el9e?
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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 of enecf lsh:-m8/ anrgy?
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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 hah4* mi,c s7obw4nyj0omemade “telephone” 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 traveys7n4omw hac i0jb4*, ls 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 arsdu5)d4s8 ofrequency or wavelength du 4d58saor s)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 st2( .3vhl1yuc (in hmn3ghl g3peed of sound in air does not depend signifih2mnth .gh3l ncil(y31g (3 uvcantly 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 ve 7a7 oyc wste/ ool6ynqr5(,g8ry high-pitched. Why?
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7#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
How will the air temperature in a room affect the pitch of organ pip2y7uk 69r8yrtwy ce d-es?
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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 todok7 ++z*p*s4wnf(8 cqp23 jh +m czvjzdtl9 t reduce the amplitude of sounds in various frequency ran+ zt4+ozp*w lz9q(cjm+d8 kvj2p3 7h fdstn c*ges. (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 together as y-e*vpxrs *e)k 14we 0e xpy7taou move up the fing)y**7pres w0p x4ee- ae1xvtkerboard toward the bridge?

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10#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A noisy truck approaches you from behind a building.1(s n; .rvcr1ztu,ys r Initially you hear it but cannot see it. When it emerges and you do see it, its sound is suddenly “brighter” — you hear more of the high-frequency noise. Explain. [Hint:yr;t,n.1u r1 v c(rssz 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 ao9jlvd * .xyjj2 d++v“interference in space,” whereas beats can be said to be due to “interferen+9dv2jx.+yjo jla*d vce 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 frequent p1apv,sedjse+zaqg *i pq9,+ :p-n-cy of the speakers were lowered, would the points D andspieaq+e,p pq,z g:--s +1vdtn9a*j p 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 the hearing of peddbz5 yn n d86mifzumb g;7;+6ople who work in areas with very high noise levels have consisted mainly of efforts to blob; 5dnbmu6yzmg8dd7fz ; 6in+ck 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 Ff/1:34xvstwmqoz )r *q vay;iig. 12–31. Each wave can be thought of as a superposition of two sound waves with sl4q /;was 3xmtf)qzi: yv1o*rvightly 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 the source and observer move in the same direction, o3g x i+c2rcepb)p6+rwith the same vec2pb+rxo +) i3 pr6ecglocity? 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 frequency of the oxv6e5gx;zf l9a2l(b v-wqw/ sound heard by a person at rest with respect to the sourv 5 2lbg/wqx-wv; a6o9zle(fxce? 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 posievl/xoaep:w *0 p ib9+ tggh-3tions of a child in motion on a swing. A monitor is+* wl9xeap3 tg:gih0bpe -/ov blowing a whistle in front of the child on the ground. At which position, A through E, will the child hear the highest frequency for the sound of the whistle? Explain your reasoning.

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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 of her shol 1tdj:xwx/yr(c ti6 /ut reflected by a cliff at the ftx ljt(i /dc:r/6yw1xar 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 shipv:em+ 16a9echpz v+ or just below the waterline. He hears the echo of the sound reflected from the ocean floor directly b 6+ezmv:preva +9 hoc1elow 2.5 s later. How deep is the ocean at this point? Assume the speed of sound in seawater is 1560 m/s (Table 12–1) and does not vary significantly with depth.    ×103m

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20#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Calculate the wavelengths in air at 20 hh4;ldqmw12xca )u0i q; kl/s 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 justwah(oby ve5 o d*t5g cy3m3wk7;jl ,s- above a school of tuna on a foggy day. Without warningck*v5g-t, lyoheo3a3 5 mwwjbs( d;y7, an engine backfire occurs on another boat 1.0 km away (Fig. 12–33). How much time elapses before the backfire is heard (a) by 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 s( faiqzw ,fx39 uifl.od)) 8fgplash it makes when striking th ,9 f))gqdufl8x.aiz wf i3fo(e water below is heard 3.5 s later. How high is the cliff?    m

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23#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A person, with his ear to the grou-9zn2w glz2t b2rj ;dind, sees a huge 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 w-92dgi2 rn;jz tlbz2apart. 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 dis2 j) fu63dglzttance by the “5-second rule” for estimating the distance from a lightning strike if the temperature is (a) 32)t63 gujdz fl0 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 ( ya)y 2ykxfxhh(wddj /y++(s 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 levelzw5dh :n e49cr3 o4sn,,t tpit 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 p3cjmx;) d mhi+roduce a sound level of 95 dB when fired simultaneously at a certaincx;md)mhi +j 3 place, what will be the sound level if only one is exploded? [Hint: Add intensities, not dB’s.]    dB

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28#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A person standing a certain distance from anmssq(3s uq3 x,wi-dobv i0 h14 airplane with four equally noisy jet engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person experience if the captain shut down all, h m3d q40s3uoxi-i1 q(vbssw 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-noise ratio of 58 dB, whereapbo;y o 7+ 7nj 6ir)a;axqhlb0:8 wmdts for a CD player it is 95 dB. What is the ratio of inteit7j n:8q ;mayl )0rwx; o+7h ob6adpbnsities 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 outp3-ej. x)vlredl bo) 7aut of sound from a person speaking in normal conversation. Use Tablel-rvb. ed3)7loxj)ae 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 strikes an eardrum whose are b2 k /y 4eloh(sixpd0qk7e6)ca is 5×105m2 (a) How much energy is absorbed by the eardrum per second?    ×1012W (b) At this rate, how long would it take your eardrum to receive a total energy of 1.0 J?   ×103yr

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32#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Expensive amplifier A is rated at 250 W, while the more modest amplifier B is rc,c n6e n1 r9e/3otr.pcp-emuated 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 eut 6p/ee -nop91.c,nce crmr3 ach 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 front of a a*xihd92 ;i3 bp5d/kgk*wzxulow/ khu i5idd3 ;gk9xzpa2* xb*udspeaker 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 difference in sound level ok-) w dggvb u05)a4oxwf 2.0 dB. What is the ratio of the amplitudes of two sounds whose levels differ by this amount? [Hint: See Section 11–9.a4v 5x)0w gwobud)gk- ]   

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35#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If the amplitude of a sound wave is tripled, (a) by what factor will the3advi9 h j84vn intensity increase? Increase by a factor of d v9nihjv8a34    (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, bsyicmva13zbx4; i,t- ut one has twice the frequency of the m1bx a; i,i-3sc4tyvzother. 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 so0(r+rnj,x bq4i2h.o9k fkwy wund level (in dB) of a sound wave in air that corresponds to a displacement amplitude of vibrating air molecules r 4.,w2bkw90khi onf+jqx( yrof 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 seem6of- jxwzh c,i0ap v.3 as loud as a 100-Hz tone that has a pc ix,f v.6-oz0j 3hwa50-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 canu j0d qgo40:fux0-ayg detect when the sound level is 30 dB? (See Fig. jg 0 ou04ax0uy-g :dfq12–6.)

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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 xm9,4ip)*lqtjir grs,;. oppuok j9 5range of sound levels. What is the ratio of highest to low4r9 gl,r5k. imps o*jqxi) ,to;p j9upest 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. The lengt5q m /akla .9vv z;.930oubaifohrx(nh of the vibrating portion mbnaxu a z9/.o v(kiq3.h9o5vf; 0lrais 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 fundamental and first three ah-da; altrk/1udible overtones if the pipe is hdl1a ;-k/tra
(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 the5 5wziuj7i m g/k8n44kviesdti r.z, 0 top of an emp, i.ei kzn5 z7k8/ism4j 0v wiu5t4drgty soda 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 ra/,;b7 jw,fw nj b) cks6 bagzc5i)d1lvnge of human hearing (20 Hz to 20 kHz), what would be the range of the lengths of p)lf6d 7 /n j ;1,jcc bbsv5iwa,gkz)wbipes 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. Whael kp/x6z3 ;o mizf(0+l0nmlbt will be its 0 neo;/0mzk filpm6 zxl3+ lb(fundamental frequency if it is fingered at a length of only 60% of its original length?   Hz

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46#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An unfingered guitar string is 0.73 m long and is tuned to play E ab+t i2 bl9son;2+nuzv w ijvv-8ove middle C (33029o nt uv b+lv 8;vni-wi2js+z 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 that eo * (1xdhkcz-*zdj4 iymits middle C (262 Hz) when the temperature ck4o1d-zi x d*j*(hy zis 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 au2z5qas n:8mjis4as2t 20 C. By what percent will the frequency be off at 5.0 C?    %

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49#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How far from the mouthpiece of the flute in Example 12–10 should the hole bncl(n5cmai 6 nd/2a2xe that n/(2dm2xcna n cil65amust be 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 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 Hz66):4lr zovfp; * :lqphtxs6,zc kvio, 440 Hz, and 616 Hz, but not at any other:s)otl r4 vf;6h p*,oxz lq:66vic pzk 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 resonp61mf pxqgp78eed +8tates at two successip 178eqgp6ef mdtx 8+pve 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?    ×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 rznsf; o) po3*3q3 occq q cl1jg(g1p) 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 p( q4xy,hi y+pbi3ib*cresent within the audible range for a 2.14-m-long organ pipei+4yqbpb*3 i(y, cxih 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 outsidee7 n8o w-l2 er.7tg 8xp8tqozo and is closed at the other end by th2 - 8.oetr w7lt78 egoqxz8pone eardrum. Estimate the frequencies (in the audible range) of the standing waves in the ear canal. What is the relationship of your answer to the information in the graph of Fig. 12–6? f1 =    Hz f3 =    Hz f5 =    Hz


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56#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A piano tuner hears one beat every 2.0 s when trying to adj5eqxs k2r/ 3wlust two strings, one of which is soundi5qxrsw3k/e 2 lng 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 m up9gj+9)8* o ji)dihrkn:s ujiddle 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 whistlvh ;de0f v qjjx,efh4p;n/x-4 e operates at 23.5 kHz, while another (brand X) operates at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whine of frequenhnej e4/ vhj4v;f0,q-dx;xf pcy 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 fv+l ei 40vvok7ork and 9 bevkl 47 eov0v+iats/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 tension in onjyok lp69k sl11h+y4be string is then decreased by 2yk1y4 6bsphkl 1 l+jo9.0%. 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 Cssua2jq,u4fd:h l 7 5x (262 Hz), but one is at 5.2f:sxld7husq 5 u ,ja40°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. Forktm bexb)mu 9mb-;;-dzyu ) c3k B has a frequency of 441 Hz; when A and B are sounded together, a beat frequency of 3 Hz c z-y)t 3;um bmk9-bx ebdm);uis heard. When B and C are sounded together, the beat frequency is 4 Hz. What are the possible frequencies of A and C? What beat frequencies are possible when A and C are sounded together?fA =    Hz or    Hz
fC =    Hz or    Hz
|fA-fC|    Hz or    Hz

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63#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two loudspeakers are 1.80 m apart. A person stands 3.00 m frombk84c3+: bhpe gia0d d one speaker and 3.50 m from the otbikac:p d8dg43b+ 0heher.
(a) What is the lowest frequency at which destructive interference will occur at this point? f =    Hz
(b) Calculate two other frequencies that also result in destructive interference at this point (give the next two highest). Let T = 20 C    Hz    Hz

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64#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two piano strings are supposed to be vibrating at 132 Hz, bi);hfrfvn:4z ba*6 c9gvg 0idut a piano tuner hears three beats every 2.0 s when they are played together. (a) If one in6iv ;fcbh)di*frvz:9 40gag s vibrating at 132 Hz, what must be the frequency of the other ?   Hz    Hz
(b) By how much (in percent) must the tension be increased or decreased to bring them in tune?   % increase    %decrease

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65#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A source emits sound of wavelengths 2.64 m and 2.76 m in air. How many beatenl0t*e vze(cpv ;k,8 s per second will be heard? (Assu ( ,eevzpen8t* v0ckl;me 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 91 xr2d2fl8u ,qltmmp’s siren is 1550 Hz when at rest. What freqp8qf9 2urdl 2lmx, tm1uency do you 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 sti 2 ltlj;,jb ewixq2:l1)-nqthll. What frequency do you detect if a fire engine whose siren emits at 1550 Hz moves at a speed of 3221lxwj ,lle hnq: jq) bi;tt-2 m/s
(a) toward you,    Hz
(b) away from you?   Hz

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68#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Compare the shift in frequency if a 2000-Hz source 00h g-,;, n*mzfngzb1ovt uotis moving toward you at 15 m/s versus you moving towardog ;-,t00z1tz,mg*f buohvn n it at 15 m/s Are the two frequencies exactly the same? Are they close? fsourcemovine    Hz
fobservemovine    Hz
(b) Repeat the calculation for 150 m/s and then again
fsourcemovine    ×103Hz
fobservermovine    ×103Hz
(c) for 300 m/s What can you conclude about the asymmetry of the Doppler formulas?fsourcemovine    ×103Hz
fobservermovine    ×103Hz

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69#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two automobiles are equipped with the same single mnfj jd nd n95i;4d5*wfrequency horn. When one is at rest and the other is moving toward the wni5fd mn94nj5 d;*dj 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 ultrasonic sound waves at 50.0 kHz and receives b:py 0 /+1d zze5z3fnu,pz olzjm3g(lthem returned from an object moving directly away from it at 25 m/s What lp np3:jgzm+,3e(lybd/ 0 z zzfoz5u1is the received sound frequency?    ×104 Hz

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71#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bat flies toward a wal 7 ilko-yu3i2i xv;8qwl at a speed of 5 m/s As it flies, the bat emits an ultrasonic sound wave with freixil2o7i-vw3 yqku 8 ;quency 30.0 kHz. What frequency does the bat hear in the reflected wave?    ×104 Hz

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72#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  In one of the original Doppler experiments, a tuba was played on a mojq9t b .szw5swekn i.h-f;;;jving 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.ssif tn9hwez;q j;w .jk5b;- 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 f7q3j.*l4 +u xxgynh )u5mlqhspeeds. Suppose the device emits sound at 3.5 MHz, and the speed of sound in human tissue is taken to be 1540 m/s What is the expected beat frequency ifgl. n flq)xu5xjy743hhuq *+m blood is flowing in large leg arteries at 2 cm/s directly away from the sound source?   Hz

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74#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The Doppler effect using ultrasonic waves ol.quwz nrxqo-ja4)r 8) jv 6j-f frequency 2.25×106Hz is used to monitor the heartbeat of a fetus. A (maximum) beat frequency of 500 Hz is observed. Assuming that the speed of sound in tissue is 1.54×103 m/s calculate the maximum velocity of the surface of the beating heart.    m/s

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75#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A factory whistle emits sound of frequency 570 Hz. When the wind velocity is t54 3pu;gtvww12 m/s from the north, what frequency will observers hear who are4w ;u vp53gtwt 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 lag kaf uykv(dq95) q)u-nd if its speed at 20 C is Mach 0.33?    m/s
(b) A high-flying jet cruising at 3000 km/h displays a Mach number of 3.2 on a screen. What is the speed of sound at that altitude?    m/s

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77#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An airplane travels at Mach 2.3 where the sgm)fb 0r*zoo-p wj.i; lkq*sa /k xse5z6r)p+peed of sound is 310 m/s (a) What is the angle the shock wave m/;gaokso**wxqb)rppzjk m f5 l- er0s.z i+6)akes 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 thin atmosphere of a planet wherem ou7f/ppi,q c;x6+ct the speed of sound is only about 35;6u+mpq i cco/,p7ftx 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 z7:kawfg8g3 ,qjk13ww*kn zvwave angle it producewfwv j,38 :1gkwqzgn*7a kz3ks
(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 3*z6iup(/x zru6pnf36ii xvm /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 kmjdc i4.zoajmvp8 .1j8 above the ground flying faster than the speed of sound. By the time you hear the sonic boom, the plane has traveledj p.zjo8 1 c84.vjamdi 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 sendvj++jvy /kfr-s 20,000-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 m, what is the minimum time between pulses (inyvf jj /-v+kr+ 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 ranghs +gu,b-eoa:e?    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 7kfxshdp/e2 *-o u n9 l)rr9gba sewer pipe symphony. It consists of many plastic pipes of various lengths, which are open on both en/2eh 9fdobrgx* )nr7- k9u lspds.
(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 (t z-nkfc5ip2 zu+c,h a sound close to the threshold of human hearing (0 dB). What will be the sound level of 1000 such mosquitoe-+znf5ich u zpk2t( ,cs?    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 ae **4r.9kt:keqyb bh 2y+xdhw n 82-dB sound and an 87-dB sound are heard sihtb:9*kwdbyree xyh .kq +24* multaneously?    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 loudspezaf d ;3x+fa1maker, placed in the open, is 105 dB. What is the acoustic power output (W) of1 m+a; dfzfxa3 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. Th+2x +umqhb2gge power output drops by 10 dB at h2mqub++ 2 xgg15 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 w1(q ubtz/aq +lb4 ,ljrear 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 intercepted by an unprotected ear at a distance of 30 m from a/t(zb+u brjq all41,q 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 systef/zw(gna9jviw-o 7 ;xms, the gain, β in decibels is defined as
β = 10log(PoutPin)
where Pin is the power input to the system and Pout is the power output. A particular stereo amplifier puts out 100 W of power for an input of 1 mW. What is its gain in dB?   dB

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91#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Each string on a violin is tuned to a freb o),2n6tefayquency 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 vq 3+3c6:yrc6 j qptrrwith a fundamental frequency ofqrp:r3+6j3qty6r v c c 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 vzmc u6vehcwm3m97,l(ertical open tube filled with water (Fig. 12–35). The water level is allou e7w,9 z3(hccm6 mlvmwed to drop slowly. As it does so, the air in the tube above the water level is heard to resonate with the tuning fork when the distance from the tube opening to the water level is 0.125 m and again at 0.395 m. What is the 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 2.10mq h+68 oljcl *gq,f2o 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 proq+j ,*mocghlloq68 f2 duce 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 e;z 7oi0tp; fi p35k t;t,vovifull 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 to,2x/pdxp49x :v5pj8w o)a gjf.uupe cne in the 500–1000-Hz range coming from two sources. The sound is loudest at points equidistant from the two source 2x jcapodpj9 w4 pp8ue.:5f ,ux/x)gvs. To determine exactly what the frequency is, the person moves about and finds that the sound level is minimal at a point 0.34 m farther from one source than the other. What is the frequency of the 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-u7 h.5xx :cfmkHz whistles. One train is stationary. The conductor on the stationary train hears a 3.0-Hz beat frequency when the other tr .mk x5c7f:uhxain approaches. What is the speed of the moving train?   m/s

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98#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The frequency of a steam train whistle as it approaches you is 538 Hz. After itygk+tp; ld :a( passes you, its frequency is me (kda p;ly:t+gasured as 486 Hz. How fast was the train moving (assume constant velocity)?    m/s

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99#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  At a race track, you can e1cv xc7vz1x;ustimate 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 (frequency halv;zcxvvx7 1uc1 ed) 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 pipesq.0av(sq 9 wwy0o;l3i z.om proi-a i*, sounding together, produce a beat frequency of 11 Hz. The sho3* 9.qpo rzisw.0iaam o;q0 y-ilo(vw rter one 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 of a railroad car as it moves past a pnac2b334p 4b 0h xreustationary 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 bpah2cb43r e4n03x pucar, (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 the aorta is normally about + yu9 7f0 g3dd)n;g9cbb.a+mqnoggou 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 tr7 g d+9)dgbo.q0 ubc 39m+oyungag;nfavel 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 m x1t0 iqdudt*eg,g:;at speed 6.5 m/s while the moth is flying toward the bat at speed 5 m/s The bat emits a soundd mdt:e*xg, 0 ;itqu1g 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 frequeee p1k)ru/rnbzc645w 9x 9ptw ncy sound pulses as it approaches a moth. The pulses are approximately 70.0 ms apart, and each is about 3.0 ms long. How far away can the moth be detected by the bat so that the echo from one chirp returns before the nextx b e w/t46)r9ezrpkp19cu 5wn 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 u(qdmdyssus*f. e7o 9j--qtd/b ::fupsed 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 -qjs*t:u:79.msep (q- d dffyodu sb/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 com(l;ofcv;ggf,m 39v empromised by the presence of standing waves, which can cause acoustic “dead spots” at the locations of the pressure nodes. Consid f(9mo;vf g3c;,melgver a living room 5.0 m long, 4.0 m wide, and 2.8 m high. Calculate the fundamental frequencies for the standing waves in this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

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107#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A dramatic demonstration, called “singing rods,” involves a long, slend+ ovns9(7n )qj xyjaf-ld2h, xer aluminum rod held in the hand near the rod’s midpoint. The rod is stroked with the other hand. With a little practice, the rod can be made to “sing,” or emit a clear, loud, ringing sound. For a 90-cav2 (jxoq )7sxd+-ylf jhn, n9m-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 frequency o;sgm; l8uvk.i d h(k+7blr :a3zozs *jf about 10dk7:s(ig l. ;*zlvz8;m hjbsuk+a 3or00 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)gf*a*io i d)wkv, li/ on the ground hears the sonic boom 1.5 min after the plane passes directly overhead. What is the plane’s altitude?v)dwia/*i,* kgl)f io    ×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 is(xqj 8qqhc310npt 4ud 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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