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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 that sound travels+jb jv g-)iwe2px8:yq 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 s1oyb zn.*h q 4jhzqv*-ound is a form of energy?
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3#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Children sometimes play with a homemade “telh b /,f9w:.hx ppx5eoj0xwyb4 ephone” 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 .xex:/bphwj4bpox5w 09 f,yh 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 frequ+bcjzpu do;hbtq8xmc2 k3: w/h75ff :ency or wavelength to change:z3bh8fod5 hc:;tmj7/w xubf p q2 ck+?
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5#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
What evidence can you give that the speed bh2+ so5vm mz*ay)q20sc7o xwof sound in air does not depend significantly oc*+mwqbsmoaz2v) x0 shy 527 on frequency?
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6#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
The voice of a person who has inhaled helium sounds very high-pit*apph*m h9+9bhjdj z 2ched. 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 or2, ij(;hkv6p7-,gd0lquvn ubx w z zn9gan pipes?
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8#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Explain how a tube might be used as a filter to reduce the amplitude of sp7txjv2o3 6w 9kr7guzounds in various frequency ranges. (An examplz7xo p7k29uj w3r6vgte 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 vo6j0.z3mbhtm0+ ewg qvo hh q 8kzxb.c+5t19you move up the fingerboard toward the br h.b 500ooqtvh6c.hqjb+z 3me1k t m8z9gv wx+idge?

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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 buildc7wwc: v vg,9zing. Initially you hear it but cannotzvvcw 9 g7wc,: 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: 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 “inte e+pjn )a 7vz9gv+ezy12dhks6rference in space,” whereas beats can be said nyd1j+e )zvs9gzp +hvk 7ea 26to 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 the points rg1lwe 0(lfzxkc 2+c;D and C (where destructive and constructive interference occ f (+zw ;k01lxegcc2rlur) move farther apart or closer together?
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13#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Traditional methods of protecting the hearing of people who work in areas with v.mxtrg37 qcdemych.+ jkm (ze7*(a n +ery 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 it electronically, then feeds it to the headphones in g3m c7rh(znya xk7cqtm(mej. +.+de*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 w5ra e-* u9xpswkx 9j 4unw(7gin Fig. 12–31. Each wave can be thought of as a superposition of two sound waves with slightly different frequencies, as9w7(4 ka xuex ngrjp9u5*ww-s 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,po-8 )wdhb+r uwfs:d. with the same vehwbwfd s 8 .+)d:u-oprlocity? 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 soundsuqkx5g :q ,s0 heard by a person at rest with respect to the qx0u:skq s5, gsource? Is the wavelength or velocity changed?
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17#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Figure 12–32 shows various positions of a child in motion on a swing. A moni8 e:,f ogxmi0w:kb1eotor is blowing a whistle in 0 o 1gxek om:8,wbeif: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 echod e)s jcth6 czh m h0x;c2rn+.ok3+*jo of her shout reflected by a cliff at the far ccjm okh)026x+j3 +e shtd.nz hr*;ocend 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 hhup(ow 90/* yiucmi *n1 1j:pj dpwe/cis ship just below the waterline. He hears the echo of the sound reflected from the ocean floor direct*cip(jud9 n / ju*i:1whpw 1y0eo/cpmly 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 wavelengths in air at 20 cai ixv; 5ns9nrg)sm *0g3xn 4$^{\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 sq.yo(ap w-rt5)jihard3sa0;chool of tuna on a foggy day. Without warning, an engine backfire occ p;a3(r5w.0r- sqdi jhoaya)turs 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 r(-xb)b5x fkikab-uyalh/ mt.9fc68 cliff. The splash it makes when striking the water below is heard 3.5 s later. How high is amk-.(5k - /t )xluhf9aiyb8cb bx f6rthe cliff?    m

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23#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A person, with his ear to the ground, sees a huge stone strike thq m28r4, e0 cmyvvu)rz4pojf4snz u77e concrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other in the c,u zp4o 8v 7ycsjq4)e7nmr ufzv4m 0r2oncrete, and they are 1.1 s apart. 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 e p2 lx5p8pfk3zws4xf 15m q,jlrror made over one mile of distance by the “5-second rule” for estimating the distance from a lightning strz4 pq8pf1j,k5fwlm5l x3s2xpike 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 an nss9nne9b8o,+.l5: bgks eot the pain 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 abuoc*m.e54vaz st 2,f sound whose 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 produce a sound level of 9me1 vd9ah /zi+5 dB when fired simultaneously at a certain place, what will be the sound level if only one is exploded? [Hint: Add intensities, 1 id9 /hvmzae+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 equab)0pf1c4y sts+hb s9n :o 1dyjlly noisy jet engines is experiencing a sound level bordering on pain, 120y yj+49nsp:o t)fdb10s bs1h c dB. What sound level would this person experience if the captain 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 av :v;cs c-yy*t signal-to-noise ratio of 58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensitis tcy-v: vy*c;es of the signal and the background noise for each device? 58 dB =    $ \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 from a person speag w8x go8 -gqkwr+ a0r8l7bow-king in normal conversation. Use Table 1q87wxgoalwo8 -08- wrb+g rkg2–2. Assume the sound spreads roughly uniformly over a sphere centered 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 arejjx 3309rra awa 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, whil9uea3wps8 bh+ e the more modest amplifier B is rated at 40 W. (a) Estimate the sound level in decibels you would expect at a point 3.5 m from a loud9e w+ hpsbu8a3speaker connected in turn to each 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 whe 5o+s+ +etvmimn placed 2.8 m in front of a loudspeaker on tot +e +5+isvmmhe 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 ii)nv 6t : igesyw6+pa+ lx7fi*n sound level of 2.0 dB. What is the ratio of the amplitudes of two sounds whose levels differ by thi ivn)ipts6+7y*6wxil:eagf+ s 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 wave is tripled, (a) by what factor will the 5 0sz/v9n7mu2vyzfinintensity izfnn /s 572zv 0yi9umvncrease? 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 equa;hk ag;7rj1iul displacement amplitudes, but one has twice the frequency of the other. What is the ratio of thh7;ra1k ;uj gieir 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 (inya,m r;2,8ozy4 d v4opur(k ms dB) of a sound wave in air that corresponds to a displacement ao 2,dp(ov;myk4 yzrrms,u a84mplitude 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 havtholpnbck 3 g,0 kr7(4e what sound level to seem as loud as a 100-Hz tone that has a 50-dB sound level? (See F b0o7t 4n k3clk(prh,gig. 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 aya u6 *chidr5o9iahf4e)l/ 6kn ear can detect when the sound level is 30 dB? (See Fig. 12–c *y) ielua 64r5odkhif/a9 h66.)

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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. Whahrdlg9t+6rgvck8ltmcw3 l- c :l:x )2t is the ratio of highest to lowest intensity h kg::)+2v-3l l96d wmgrlctrtl8ccxat
(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 freq1dxu6p ebj98q i0jdo .uency of 440 Hz. The length of the vibrating portion is 32 cm, and it has a mass of 0 qi1 j0u.9ddoex 8bj6p.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 firsto yl- ahr(y+k(l x 88umzrvi./ three audible overtones ik .v8(-lmx(hr+yu z/oarl8yif 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 yfl w56;r.w(0 op uelyan empty soda bottle that is 18 cm deep, if you a0;w u.w 6 eyrp5oy(llfssumed 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 kx e4(4ne) 4gpsye /clpipes spanning the range of human hearing (20 ylc/gpn4e 4)(e sek 4xHz to 20 kHz), what would be the range of the lengths 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 has a frequency of 540 Hz as its third hl-qdk, qtu9kk q)n3*yarmonic. What will be its fundamental frequency if it is fingered at a length of only 60% of its original lqk-ku dk l9),tqq n*y3ength?   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 0.7es5dnngn 8o.gpy:6 1 f3 m long and is tuned to play E above middle C (330 n:gnfeop .6gn518dy sHz).
(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 length of an open organ pikptp *iaj21 76tv0hebpe that emits middle C (262 Hz) when the temperature ip ea* t6hj1i02kb7pvt s 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 20k378evij h6 +vtw7teke e 2f5a $^{\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 mouthpiece jrf o6z,kft.o2u3k p4of the flute in Example 12–10 should the hole be that must be uncovered to play D above middle C o j6z3kp.f 4,u tkfro2at 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 Hz, b)go px5w 4)rawut not at any other frequencies in between. (a) Show why this is an open g)ap5r)wx4wo 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 e9 cllixyuq7;ohl 4). ok21 cfdnds. It resonates at two successive harmonics of frequencies 275 Hz and 330 Hz. Wio xk19l4c dly 2c) .;qfuh7lohat 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 q1l3a1jht9ed+mib w e1 dm:4a $^{\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 przq9r6yrj v,b.esent within the audible range for a 2.14-m-long organ p9 q .yvzbrr,6jipe 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 lo 7;+qzw4zvcnfn6w /t png. It is open to the outside and is closed at the other end by the eardrupwzn4wq cnf+;/v 7zt6m. 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? $f_1$ =    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 one beat every 2.0 s (:0okgyhf r,i8.waw bwhen trying to adjust two strings, one of which is sounding 440 Hz. How far off in frequency is the ot.0ior, gayk8h(w fwb :her 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 freq45czo*m9uz7fi -vb mle/k*um uency if 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)? $\approx$    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) oqu7f+2.g g. cd k1j5lvbt6 iskperates at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whine of frequency 5000 Hz occurs when they are pcb 5qugi+6g d1f.l kvk.7jst2 layed 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 for7v49 i(3zh v s5u, k:rsqpeovpk and 9 beats/s when sounded with a 355spv psq(e :9 ,z4oi5hrukv73v-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, 29 /4 9lz+ *dggtnzvwcw54 Hz. The tension in one string is then decreased by 2.0%. What will be the beat frequency heard when the two strings are played together? [Hint: Recall Eq. 11–13.]9*lwznctw +5 /g4gd vz    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 heardp8 lss5ia7,iv nr u5h/ if two identical flutes each try to play middle C (262 H5r i ,vp5l i/7s8nhuasz), but one is at 5.0°C and the other at 25.0 $^{\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 ae uv( l*fko4:g94nwji frequency of 441 Hz; when A and B are sounded togeth4 ji l:vge9wukf4n(o* er, a beat frequency of 3 Hz is heard. When B and C are sounded together, the beat frequency is 4 Hz. What are the possible frequencies of A and C? What beat frequencies are 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 person stands 3.00 m from one speaker and r zl9 9lyv*9qm3.50 m from the other. 9m l *zrl9vy9q
(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 132 Hz, but a piano tuner 6wazw+wf h ti*,/;al6;i jcwo hears three beats every 2.0 s when they are played together. (a) If one is viwi+z;w fi/tjc ww h 6o,;laa6*brating 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 *9 fnxf6d, q4doec :fd3riz-a.64 m and 2.76 m in air. How many beats per secofd4fozrnx9 *3 ,c a:q-di fde6nd 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 frequencyg6p zetij5j lz1/4,)pt + qctw of a certain fire engine’s siren is 1550 Hz when at rest. What frequency do ljticjt)pz /5 t4+,pg6z qwe1you detect if you move with a speed of 30 m/s
(a) toward the fire engine,    Hz
(b) away from it?   Hz

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67#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You are standing still. What frequencyj5bl,*7ujkk 7kt5w x t do you detect if a fire engine whose sirenk7k7ux,k5* jbwt5j tl emits at 1550 Hz moves at a speed of 32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

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68#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) Compare the shifttslul1u+ ;bzi3b p73n in frequency if a 2000-Hz source is moving toward you at 15 m/s versus you7 3bi+ ;lluzptnbu13s moving toward it at 15 m/s Are the two frequencies 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 withh9epkp3f2 n *;m fhsnhdq3spv)z69-ff1 g ep9 the same single frequency horn. When one is at rest and the other is moving toward the first at s32p9qp1ee hff;9h kpdfs- pm39gnn zv)f6h *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 50.0 kHz and receives they)sqz l1 a9aswz52x1mm returned from an o 1sm2slzz)xy51 waaq9bject moving directly away from it at 25 m/s What is the received sound frequency?    $ \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 of 5 m/s 1:l4fujcnhu1l. l)f hAs it flies, the bat emits an ultrasonic sound wave with frequency u .:fh1ln uj1l 4)lchf30.0 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, a tuba was played on chm onx.flw02a 9+g1m a moving flat train car at a frequency of 75 Hz, and a second identical tuba pla92xlg m fchn 0a1wo+.myed 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 usest:: z. ak32qqgjw l6bu )h3ejx ultrasound waves to measure blood-flow speeds. 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 i ) qt2hue .jk336bwxlgq:jz:af 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 of freq *7nlzcdonc c6i:)2f kuency $2.25 \times10^{ 6}$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 sound of frequency 570 Hz. When the wind v9ahsd evg 36u4 l4sp2nelocity is 12 m/s from the north, what frequency will observers hear who a as u49nhv34 62pgledsre 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 mwj,g1jygw gaq s*ys-:pm1 ; b-cmi0 2 +ztbr8speed at 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 Mac esdj o5.md gus9i63gd() 5,r+z cwqtth 2.3 where the speed of sound is 310 m/s (a) What is the angle the shock 95+d,rtssot(d6zwue j 3dmgig ) cq.5wave 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 whers cvfvcvbg9)*x5 m:,k ,tyu;oe the speed of sound is only about 35 m*,ob: ys5ftcvxk ,mvug9 vc;) /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. Determine the shock waver)0aq90m4u2ek +gkgju; x wad angle it produceq 2 wxumgk0 e+adj90;a4)kgurs
(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 ,n 7ajvqbth/dn/huk(p. (o3d$/theta$ 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 - wh 0s p)*x3heaz6hdkplane exactly 1.5 km above the ground flying faster than the speed of sound. By the time you hear the sonic boom, the plane has traveled a horizontal distance of 2.0ep)*zh6a dk03x -hwhs 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 sound5i pcpa.* wvo1 pulses downward from the bottom of thp*1c .5ow apive 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 (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 hc*g jc s ozgy33 a.lvs(a5iy/9.gm m7luman audible range? $\approx$    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 called a sewer pipe symphony. It consistfjuque1m6c) qvh2l;6 x)t2f cs of many plastic pipes of various lengths, which are open2 fm;2x6) qqjelu )hc1vtu6 cf 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 sound close tjef4 h4fh5 p4ro the threshold of human hearing (0 dB). What will be the r4 eff4 45hphjsound 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 souzbkxc5 wao+ w)ozkd;r-f:a 9-nd are hearw ok5c-d+za- af)k9b:xwz r;o d simultaneously?    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, plai)k g c2j+)cevli:f+o4 )rzgpced in the open, is 105 dB. What is the acoustic power output (W) of the speaker, assuming it radiates equally in all dij vel+pig2gc4kf )i rz)co+) :rections?    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 vl7rg/k)f phgr3 y+7bqu9 gc*W output at 1000 Hz. The power output drops by 10 dB at 15 kHz. What is the power output in watts a9rlgh7 rc f+gkbp)y 7q3*g/v ut 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 typiilk,m ;/dns e x poia6l -p70q f.9xri*l;d.uocally wear protective devices over their ears. Assume that the sound level of a jet airplane engine, at a distance of 30 m, is 140 dB, and that the avei.lx i; pp;nf/dique 6,m9o k a0xrod-sl7.*lrage 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 syst h8u15u(3qg q*czrr ndems, 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 tune)c+sm6 - d:xmvgf64-epqqwa wd to 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 vicgy *gre-:no +olin is 32 cm long between fixed points with a fundamental frequence* -cngyor+g:y of 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 a vertical open tube filled withr : v t(./v yujpxd(ygdys)71o water (Fig. 12–35). The water level is allowed to drop slowly. As it does so, the air in the tube above the water level is heard to res/o:g(vv.py1ydr7j (uytd s x)onate with the tuning fork when the distance from the tube opening to the water level is 0.125 m and again at 0.395 m. What is the frequency of the tuning fork?   Hz


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94#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 75-cm-long guitar string of mass 2.10 g is near a tu orvcij3 xz12+be that is open at one end and also 75 cm long. How much tension should be in the string if it is to producixr1 o+ 3vjzc2e resonance (in its fundamental 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 full loov1;dn w 1iq8wyp ($\frac{1}{2}\lambda$) 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 frxzdz/8tptlpv (ib op6(gj ):, om two sources. The sound is loudest at points equidistant from the two sources. To determine exactly what the frequency is, the person moves about and finds that the sound level is minimal at a point 0.34 m farther from one source than the other. What is thet lpopd6)ip:vx/, (g8z(tbzj frequency of the sound?   Hz

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97#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two trains emit 424-Hz whistles. One train is stationary. The co1 ts- bv)tee5 j/z8qxl1 i-rupnductor on the stationary train hears a 3.0-Hz beat frequency when the other train approaches. Whax1rz8lj)b p1--tt evsq/ue5 i t 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 d/2w vgl1 .ov9afxl5j538 Hz. After it passes you, its frequency is measured as 486 Hz. How fast was the train moving (assumeg/wlojxl1 5dfv 2.9 av 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 jk(1 i6a- uxix0wsj1jh ust by listening to the difference in pitch of the kj01xi(sh ui1j -6xwaengine 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 going?    m/s

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100#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two open organ pipes, sounding together, produbezth(3 qr8(etm-b-q/-onf xce a beat frequency of 11 Hz. The shorter one is 2.40 m long (bz8-mt t q-x3ebhr/(eonq-f. 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 ra5s q((awlji j*6a,nv d rd:va/ilroad 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 frequency heard by the observer when (a) he listens from the position A, in front of the car, (b) he /*s6, ljniada dvv5: (ar( jwqis 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 if*ll8e isi;xao 9(2u xdaq64 ds 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 blsi98a(xfl;do*l 2 a euidq4 6xood cells? Assume that the 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/sz 1 hrx5.32z)zbrq 52bbs xfix while the moth is flying toward the bat at 2 br15 3rx 5bxfqx2bsz)hiz.zspeed 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 n3k;d1 bl/-edd8t;mb xw ml5tsound 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 t/tw m;5dd;be- kd13mn8 xtl lbhe 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) w(dmw2kbf j6/ kas once used to send signals from one Alpine village to another. Since lower frequency sounds are less susceptible to intensity loss, long horns werewbdk /6(f2jkm 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 listenip yl r4 yfaly6s6ug7iz(j:1a3ng can be compromised by the presence of standing waves, which can cause acoustic “dead spots” at the locations of the pressure nodes. Consider a living room 5.0 m long, 4.0 m wide, and 2.8 m high. Calculatp6r6(sf 1l3ujgaz4 7yy y:ilae 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 lon5 gpo8qpj f(ct5 0m5xfg, slender aluminum rod held in the hand near the rod’s midpoint. The rod is stroked w58g pmxfjtcf p0( 5qo5ith the other hand. 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 the human ear at a frequency a szx:dl4 bwtg-cy:lxr 2j5 epr)8s:8of about 1000 Hz : 25rj8g:lla)r-4 8ebpyxdtsxws:cz is $I_0$ = $1 \times10^{12 } W / m^2$ 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 hears the sonic p/4bex so ;v3dboom 1.5 min after the plane passes direcov e;sb4x p3d/tly overhead. What is the plane’s altitude?    $ \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 is45rrf 9q: um-qg /ewzc 15 $^{\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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