What is the evidence that sound tramq/ qoqivtm-i5c qo7h (271 qfvels as a wave?

What is the evidence that sound is a form of energy? ah37+ dyb cx3vyy-sc0 m)wa7 ,ydu5lk

Children sometimes play with a homemade “telephone” by attaching a string to thhjorz 0 ieblrfpft3 7n5+09v7 e bottoms of two paper cups. When the string is stretched and a child sperv0e hl tj+b3f7rf5z70 9ip noaks 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.

When a sound wave passes from air into k+irk1 qut0 s.hq5gi5.4xof/ h zqe)qwater, do you expect the frequency or wavel.k5/h04thqq i1 ruezi q q )5g+.fskoxength to change?

What evidence can you give that the speed of sound in air does not drx1-cgyackdcsj(7i q:5 1o w9epend significantlrgodcc51skx yc-aq7j :iw 9(1y on frequency?

The voice of a person who has inh4k pv1dso0nud pi*02j;s, hew aled helium sounds very high-pitched. Why?

How will the air temperature in a room affect the pitch of or8+ i jbk:xbym-gan pipes?

Explain how a tube might be ujow ;-nbr+.l bsed as a filter to reduce the amplitude of sounds in various frequency ranges. (Anonl+ wrj.;bb - example is a car muffler.)

Why are the frets on /9mtjzjg66: gzt0 rrf2mo8 aba guitar (Fig. 12–30) spaced closer together as you move up the fingerbf6 tr 6o8trgzj2 mb/:jgmz90 aoard toward the bridge?

A noisy truck approaches youk9ik-++afix;rhl 9w l:(+3ficn fopw from behind a building. 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 l- koxckw;pin+r +3(: i9f w9alfh f+ihigh-frequency noise. Explain. [Hint: See Section 11–15 on diffraction.]

Standing waves can be said to kgqr/n6ejh5.b uxr48 4b ww9ruvy4d;be due to “interference in space,” whereas beats can bq;5ku gv dx9w4y4errb/j84b rw6un h .e said to be due to “interference in time.” Explain.

In Fig. 12–16, if the freqpg pzu)1u, mry0qeoh*yc* i 3+uency of the speakers were lowered, would the points D and C (where destructive and constructive interference occp+) i0myyh* * 1uugr,oe3qzcp ur) move farther apart or closer together?

Traditional methods of protecting the hearing of people who work in are75ojv 8krc h hzyg264das 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 it electronically, then feeds it to the headphones in addition to the ambient noise. How could adding more noise v6 4crj7o zygh52dk8hreduce the sound levels reaching the ears?

Consider the two waves shown in Fig. 12–31. Each wave can be thought of ruga . dg:;,gvd,xm fy(hfl:*0c 1lhsas a superposition of two soun xy1* caf ,:u m.rgv;ghdhfd:gs(0,lld 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)

Is there a Doppler shift if the sod bntzi3o x8n3, p94+dzgnu/gurce and observer move in the same direction, with4gzzddpu3 ix, /g b38t+nn 9on the same velocity? Explain.

If a wind is blowing2)lxp) op4 ofo, will this alter the frequency of the sound heard by a person at p lxof2)4 opo)rest with respect to the source? Is the wavelength or velocity changed?

Figure 12–32 shows vatg u 4uly9q1) og3ji(arious positions of a child in motion on a swing. A monitor is blowing a whistle in front of the child on the ground. At which position, A through E, wiug4j(u3tqoil91 y) agll the child hear the highest frequency for the sound of the whistle? Explain your reasoning.

  A hiker determines the length of a lake by listening for the ecxab* s9w a.c;b0 p7 j5yxw*; tzy:gqoh5: zxzmho of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.0 s after shouting. Estimate the length of the lopwhb09ayt*z*abs .x5x7 : xwqg;:y;zcj5 z make. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his vr1u,r.f,dm(0rvzjff 5)l dbwa.tx + ship just below the waterline. He hears the echo of the sound reflected from the ocean floor directly below 2.5 s later. How deep is the ocean at this point? Assume the speed of sound in sr(ubvda0)jr1z+wfd. .tlvm,5 ,xrf feawater is 1560 m/s (Table 12–1) and does not vary significantly with depth.    $ \times10^{ 3}$m

  (a) Calculate the waujy,7qwnpx 7, velengths 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

  An ocean fishing boat is drifting just above a school of tuna on a foggy day7)fqe /*v h6no cet4+hw3bzyy. Without warning, an engine backfire occurs w)ot7ey4q *h hycb3e vzf6+n /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

  A stone is dropped frombya qmb02g+zv8zas7 + the top of a cliff. The splash it makes when striking the water below is heard 3.5 s later. How high is the m+z 7zv a8gba2b+y q0scliff?    m

  A person, with his ear to the ground, sees a huge stone strike the concrete pav:zko 7 ny30lanement. 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. How far away did the impact occur? See Table 3 7o 0kaynnz:l12–1.$\approx$    $ \times10^{2 }$m

  Calculate the percenxt;wqvr(z d4 9tuz.rv03j /ait error made over one mile of distance by the “5-second rule” for estimating the distance from a lightning strike if the temperature tvtrri.vaz9uw4dx;/qz 30(j is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity of a sound at the pain level of 120 dBlco6z p :*k *iz,nbn0y?    W/$m^2$Compare it to that of a whisper at 20 dB.    $ \times10^{-10 }$W/$m^2$

  What is the sound le6 p)ml fqlwn8-vel of a sound whose intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sou34niwucauk .uczc 4(m - 9sec7nd 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, n i.kecu9cu(3z 4mc74as n-ucwot dB’s.]    dB

  A person standing a certain distance from an airplane with four equally noisy j6/6k5q6o u fp:odrewc et engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person exper6:5d6 owko crpeq /uf6ience if the captain shut down all but one engine? [Hint: Add intensities, not dB’s.]    dB

  A cassette player is sai +suia)0em8p, bzlgb0d to have a signal-to-noise ratio of 58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensities of the signal and the backmz bg0bu +)8l0,apiesground noise for each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of sound from a person sv,67j yp:gs0so*sgopra9c0 hpeaking in normal conversation. Use Table 12–2. Assume the sound spreads roughlyv0og 7cp:spya* sr9 6sh gj0,o 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

  A 50-dB sound wave strikes an e *iz l7-szpdzub8 g7r0c,ong0ardrum whose area 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

  Expensive amplifier A is ragkk) x(7 uzsqfdc2 p(w1mqa6p , j-gb(ted at 250 W, while the more modest amplifier B is rated at 40 W. (a) Estimate the sound level in decibels you would expect a(26p )qasjf,1mkk-(qx b uz(d 7ggwpct a point 3.5 m from a loudspeaker 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?

  At a rock concert, a dB meter register/ fr qy:)a8xi off*uxq;(y2yzed 130 dB when placed 2.8 m in front of a loudf/(ax*q:f zy ;iox2ur qf)8yyspeaker 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

  Human beings can typically detect a difference in sound level of 2.0 dB. What iszv03 , hs 7frppcoqg+9 the ratio of the amplitudes of two sounds whose levels differ by this amoup70cpqvo ,rzh9 3+fsgnt? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound wave is tripled, (a) by what factor will 8ref )eac hp8f.(ij-na;a )ktthe intensity increase? I 8p f.a-in t)efc haeka;)8rj(ncrease by a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal displacemen htzg v*a0lpcc5mf24,wc 2 j;rt amplitudes, but one has twice the frequency of the other. What r0z;t,vcl2 5c4gfm hc 2* jawpis the ratio of their intensities?   

  What would be the sound level (5lb:vq ;lv :ind l. 0j-maqohe3,rpr 8in dB) of a sound wave in air that corresponds to a displacement amplitude of rl.o br-qq l8h0li3 5 vm,ped:na;v :jvibrating air molecules of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level to seem as loud as )pp8l +jy 7nqx.)ghc7qxvizcb4 a1f*a 100-Hz tone that has a 50-dB sound le4a vq)c+7x.jfbp zi 1gnp)* cxl87hqyvel? (See Fig. 12–6.)    dB

What are the lowest and highest frequencies that an ear can d95k f5v rs(4c* +xpxtsolc m2letect when the soundsltkro9xfmc 5 x4 lp 2c(*5s+v level is 30 dB? (See Fig. 12–6.)

  Your auditory system can accommodaj+p2s c2q. m98l eljm0b gul+bte a huge range of sound levels. What is the ratio of highest to lowest in+uj bse0l2m2p lm+q. 9cj lgb8tensity at
(a) 100 Hz,$ \times10^{ a }$ a =   
(b) 5000 Hz? $ \times10^{ a }$ a =   
(See Fig. 12–6.)

  The A string on a violin has 3)0o83 nxti, bsqepjc a fundamental frequency of 440 Hz. The length of the ejs830cpn t x3o)bi,qvibrating portion is 32 cm, and it has a mass of 0.35 g. Under what tension must the string be placed?    N

  An organ pipe is 112 cm long j/rg2jvwwsn1nzdo : *:mt /h*di-kc-. What are the fundamental and first three audible over k12 t*j-sjww-/:dn rodz:mn*/chvg itones if 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

  (a) What resonant frequency would you expect from blowing across the top of an eorlts5 70v* vqzao88ampty soda bottle that is 18 c* 58o7lv08rtvqzaoas m deep, if you assumed it was a closed tube?    Hz (b) How would that change if it was one-third full of soda?   Hz

  If you were to build 3;0tidzw 3d jba pipe organ with open-tube pipes spanning the range of human hearing (20 Hz to 20 kHz), what wou jwtid3;3dz 0bld be the range of the lengths of pipes required? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

  A tight guitar string has a frequency of 540 Hz) cu.c4gjrc jzr 87a/jl9c 5hh as its third harmonic. What will be its fundamental frequency if it is finghlz48agcj 5hcr/7j .j u)cc r9ered at a length of only 60% of its original length?   Hz

  An unfingered guitar string is 0.73 m longtpcbkp f )781g and is tuned to play E above middle C (1ftbpk7p )c g8330 Hz).
(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

  (a) Determine the length of an open orgamtu k.j-bt d31y0h9pu n pipe that emits middle C (262 Hz) when the ttujhym9. u0 b -t13dpkemperature is 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

  An organ is in tune at 2.xnfb*8w h2j5 j; zjtedr,mw 20 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece of the flute in Examp al9k a/vy xz5xlg/p;9le 12–10 should the hole be that must be uncovered to play D above midd9 la xkl/v5z/pa9xy g;le C at 294 Hz?    m

  (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

  A particular organ pipe can resonate a . ja32cd*kbtjf iq .6/x3wyzyt 264 Hz, 440 Hz, and 616 Hz, but not at any other frequencies in between. (a) Show why tdj c/ 2iyxjb6tfw *33zy.ak.qhis is an open or a closed pipe. ----待选择----closedopen  (b) What is the fundamental frequency of this pipe?   Hz

  A uniform narrow tube 1.80 m long is open at both enf)rc j2xz ni1ks+ssn0k1n0 72 dvo sf/ds. It resonates at two successive harmonics of frequen 7dcj20ss 2)+/11 sknrs noifnx k0vfzcies 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

  A pipe in air at 20 45* 9fbjp y66c iaybzb$^{\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?  ----待选择----closedopen  f =    m

  How many overtones are present within the audible range for a 2.uku9c-x+tjfd*s; (:: jmxuwl 14-m-long organ pipe at:xw+mj9-*u ; fk (uj:cldstxu 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximately 2.5 cm long. It is open to the.yu3ig1a gbav:i)- n s 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 of your answer tonu3va .1y)bg -aig:is the information in the graph of Fig. 12–6? $f_1$ =    Hz $f_3$ =    Hz $f_5$ =    Hz

  A piano tuner hears one beat every 2.0 s when/nf o+)apl-, jf-zna4 k1ykek trying to adjust two strings, one of which is sounopea4kznn 1 kfy,)fjl - /+ka-ding 440 Hz. How far off in frequency is the other string? ±    Hz

  What is the beat frequency if middle C (262 Hz) and o4cex r q..n-ba,h9n eitik(( $C^＃$ (277 Hz) are played together?    Hz What if each is played two octaves lower (each frequency reduced by a factor of 4)? $\approx$    Hz

  A certain dog whistle operaw0qmtzr t9u 10tes 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 frequency 5000 Hz occurs when they are played simultaneousl9ttur1z qm 0w0y, estimate the operating frequency of brand X.    kHz

  A guitar string produces 4 beats/s whs6pdwo 90ngzc-2m a0l6vweec+.sz-hc* -z s ven sounded with a 350-Hz tuning fork and 9 beats/s when sounded with a 355-Hz tuning fork. What is the vibrationsgss06v6de+wpmh cz-z. 0w-- vec9ozan l2* c al frequency of the string? Explain your reasoning.    Hz

  Two violin strings are tuned to the same fr :t:l0lt6kumx3av:wu+r be ;uequency, 294 Hz. The tension in one string is then decreased by 2.0%. What will be the be k+ru:3t x:ev mb;ultu lw0a6:at frequency heard when the two strings are played together? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be heavgdn(vd)rm 84u. 9 vuhrd if two identical flutes each try to play middle C (262 Hz), but vd48hun.9)mvdu( vgr one is at 5.0°C and the other at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning f* ih v:5dy14ih *nobxzorks, A, B, and C. Fork B has a frequency of 441 Hz; when A and B are sounded together, a beat frequency of 3 Hz is heard. When B and C are sounded togetheyn: 5d*1vh zi*4obixhr, 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

  Two loudspeakers are 1.80 m apart. Aki3oon3z 6 w,x person stands 3.00 m from one speaker and 3.50 m from the otheriw33oxn 6o k,z.
(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

  Two piano strings are supposed to be o e8wz3*p dgjc4p16swvibrating at 132 Hz, but a piano tuner hears three bedwepoz41w8 gjs3 6pc *ats every 2.0 s when they are played together. (a) If one is 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

  A source emits sound of wavelengths 2.64 m and 2.76 m in air. How many beats m6 byop tx4ejfg80-+mper second will be heard? (Asyp 40 8ojtmmg-6ef+xbsume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain firx -bg7y8ibcv3 alyn7 /e engine’s siren is 1550 Hz when at rest. What frequency do you detect if you move witil7yb 3x7- c8aybg/vn h a speed of 30 m/s
(a) toward the fire engine,    Hz
(b) away from it?   Hz

  You are standing stilq )k *u82-gb jelmdmcy)-sda4l. What frequency do you detect if a fire engine whose siren emits at 1550 Hz moves at a speed of 32 m8bkqu )*ymd4jc2-asmel d )g- /s
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift yfd5 1vb(0rb ub(b5c4l0v li rin frequency if a 2000-Hz source is moving toward you at 15 m/s versus you moving toward it at 15 dbl5v014 (b bfl5r c(buv yr0im/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

  Two automobiles are equipped with the sqz 1h.lvqygm tyg,. jq+qak98u98f r1ame single frequency horn. When one is at rest and the other iyr qz.fugqj+ q y8.q9h11l8, a9vmktgs moving toward the first at 15 m/s the driver at rest hears a beat frequency of 5.5 Hz. What is the frequency the horns emit? Assume T = 20 $^{\circ} $C    Hz

  A bat at rest sends out ultrasonic sound waves at 50.0 kHz and receean6bkawe./h5n) . lgzn*if 5ives them returned from an object moving directly away from it at 25 m/sw e b.ngenalzaki 5/.)hn*f6 5 What is the received sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed of 5 m/s A x,;jo2k/uw )hfzwp s2s it flies, the bat emits an ultrasonic sound wave with frequeps/2 u; jxko2hz)fw, wncy 30.0 kHz. What frequency does the bat hear in the reflected wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experiments, a tuba was playej+-rgdtrr4cf( -l 6y dd on a moving flat train car at a frequency of 75 Hz, and a second identical tuba played the same tone while4( r+dfrgd-j 6-tly cr 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

  A Doppler flow meter uses ultrasouq9kk,nvzja+ , nd 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 154 ,kj +nvzk9,aq0 m/s What is the expected beat frequency if blood is flowing in large leg arteries at 2 cm/s directly away from the sound source?   Hz

  The Doppler effect uz(qw y:r/5ppqwz2+ cjsing ultrasonic waves of 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

  A factory whistle emits sound of frequency 570 Hz. When the wind vely . tj,c.2tyv6km: h;qhr4iya)bi* goocity is 12 m/s fromtch; 6tb ). rki*v.24ygyj h,amqo:yi the north, 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

  How fast is an object moving on land if its speed at 2/ 9cop/ (tyzr1qa;qbv, z awh20 $^{\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

  An airplane travels at Mach 2.3 where the speed of sound is7m.iaiw)g fw,t: q;cf 310 m/s (a) What is thf m);qit .icfgw:7a,w e angle 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)

  A space probe enters the thin atmosphere of su.fqauv 6uzkop3e6k4by)- 2a planet where the speed of sound is only usf 2)euk3o-au6k4 p.qb6vzy 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} $

  A meteorite traveling 8500 m/s strikes the ocbcrn3wf5y 2ay w37 o3iean. Determine the shock wave angle inr233ybcw7 f3 owa 5yit produces
(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

Show that the angle k3x+oy pj.6i ko( o-lg$/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly overhead and s,v/fs 0z1r e/hxcfaz/ee a plane exactly 1.5 km above the ground flying faster than the speed of sound. By the time you hear the sonic boom, the plane has traveled a hr/,/ /a sfz01cefvzx 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   

  A fish finder uses a sonar device that /cjk1 movl w.q-n k4.wsends 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 200vwkkmqlw /c- ..o4nj1 m, what is the minimum time between pulses (in fresh water)?    s

  Approximately how many octaves are there in the human audible rak42/ z)mm jjkx q3ip0gnge? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display called a sewer pipe symphony. Iz kn ;*ifw;7adt consists of many pl*dz;fn wi;ka 7astic pipes of various lengths, which are open on both ends.
(a) If the pipes have lengths of 3.0 m, 2.5 m, 2.0 m, 1.5 m and 1.0 m, what frequencies will be heard by a visitor’s ear placed near the ends of the pipes?
$f_{3.0}$ =    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?

  A single mosquito 5.0 m from ehugv k) rezzv) .nz2n7we i -u*x*1+aa person makes a sound close to the threshold of human hearing (0 dB). What will be the sound level of 1000 a e)w *z7n+g*)vuhk1r iue en-zx.vz2 such mosquitoes?    dB

  What is the resultant sound level when an 82-dB sound and an 87-dB sound axjy ,.4qrou on./qty1 q5zc-c3buqh .re heard simul1,5.z-n .y qyu4rcqbxtoq u /q3oc hj.taneously?    dB

  The sound level 12.0 m fr+cyb1ao3 mp fn:,m lb.,zfa.yom a loudspeaker, placed in the open, is 105 dB. What is the acoustic power output (W) of the speaker, assuming it radiates equally in all directi. mclm3b1ona +,bf,:ayz y.pf ons?    W

  A stereo amplifier is rated at 150 W output at 1000 Hz. The power output)du g h3ep9cw, drops by 10 dB at 15 kHz. What is the power output in watts at 15 kHz?hed )wp u9,g3c    dB

  Workers around jet aircraft typically wear p01*gm/cxbpu fqrw+d0zn : 1berotective devices over their ears. Assume that the sound level of a jet air*nzf/d1bqx+c:wbp 0e m1r0guplane 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

  In audio and communications systems, the gain, q40 8: cjntjsj$\beta$ 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

  Each string on a violin is tuned to a frequep3i eamu1/o e, s7kle0l;j-ue ncy 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?
$f_{A}$ =    $\mu_{A}$
$f_{B}$ =    $\mu_{A}$
$f_{C}$ =    $\mu_{A}$

  The A string of a violin i- t) f;r nnw+vcaa*b6:t/vuuis 32 cm long between fixed points with a fundamental frequency of 440 Hz and a mass p rtc:wa*nu /; )fbvva-i6 utn+er 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

  A tuning fork is set into vibration above a vertical oper;vzhi ct 0k5*n tube filled with water (Fig. 12–35). The 5vczi trk*h0;water level is allowed to drop slowly. As it does so, the air in the tube above the water level is heard to resonate with the tuning fork when the distance from the tube opening to the water level is 0.125 m and again at 0.395 m. What is the frequency of the tuning fork?   Hz

  A 75-cm-long guitar string of mass 2.10 g is near a tube that is open at one s k ;pitx)klnkb k- (gxor:691end and also 75 cm long. How much tension should be in the string if it is to produce resonance 19roptgkk(6s kb)xxl : i nk-;(in its fundamental mode) with the third harmonic in the tube?    $ \times10^{ 2}$ N

A highway overpass was observed to resonate as one ful5glk 7qg,ko6tl 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?

  A person hears a pure tone in the 500–1000-Hz range cjn qo41)boy 2zoming from two sources. The sound is loudest at points equidistant from the two sour1qz4 )2noyjbo ces. 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

  Two trains emit 424-Hz whistles. w5bbjzroh- qw5o7v07 One train is stationary. The conductor on the stationary train hears a 3.0-Hz beat frequency when the ozh5 jwv bw50o-r q7b7other train approaches. What is the speed of the moving train?   m/s

  The frequency of a steam train whistle as it approaches you is 538 Hz. After* 9d ujvq7w6r k)jif7b it passes yd7f9*rjbuivk6 q7)jw ou, its frequency is measured as 486 Hz. How fast was the train moving (assume constant velocity)?    m/s

  At a race track, you can estimate the speed of cars just by listening to a a/3zjdn 8ik8mqhz -+the difference in pitch of the engine noise between approaching and receding cars. Suppose the sound of a certain+ka8z zji 3q-n/ 8dmha car drops by a full octave (frequency halved) as it goes by on the straightaway. How fast is it going?    m/s

  Two open organ pipes, sounding together, produce a*vme(yduo/ 8x beat frequency of 11 Hz. The shorter one is 2.40 m long do(v/* 8ymuxe. How long is the other?    m

Two loudspeakers are at opposite ends of a railroad car as it moves ;nd 09t mdb3yd8 x4nmapast 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 is betweea ntd0m4xnb m9dyd;3 8n the speakers, at B, and (c) he hears the speakers after they have passed him, at C?

  If the velocity of blood flow in the aorta brv*ofjjv/o/80zl+ x adg0h 6is normally about 0.32 m/s what beat frequency would you expect if 5.50-MHz ultrasound waves were dfvax0/ldh8z*6 b ov0j+rjog /irected along the flow and reflected from the red blood cells? Assume that the waves travel with a speed of $1.54 \times10^{3 }$ m/s   $ \times10^{3 }$Hz

  A bat flies toward a moth at qa f5z36 oq0zq0y*dj/ dtsfrpiop948 speed 6.5 m/s while the moth is flying toward the bat at speed 5 m/s The bat emits a sound wave of 51.35 kHz. Wha*5do4ifppj/t dq8q0zro3 af 6 zyq09st is the frequency of the wave detected by the bat after that wave reflects off the moth?    kHz

  A bat emits a series of high frequency sound pujigv7.iv2l g.d 0uve2ecm/x4kqe3 e0lses 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 nexdvi x uv l2 eegme .02kg4ec/j.7iq3v0t chirp is emitted?    m

The “alpenhorn” (Fig. 12–38) was once used to send sigvr2+wh c2f5hjnals 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. Wha5+hrfh2 wv2jc t is the fundamental frequency of this horn, and which overtone is close to F sharp? (See Table 12–3.) Model as an open tube.

  Room acoustics for stereo listening can be compromised by the presence of standa--t*.e o1be *xeefubing waves, which can cause acoustic “dead spots” at the locations of the pressure nodes. Consider a living room 5.0 m long, 4.0 m wide, and 2.8 m high. Calculate the fundamental frequencies for the stabeeo.fee *x-1b*ua-t nding waves in this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

  A dramatic demonstration, called “singing rods,” involves a long, sl2eh+sl i6( ookender 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,h s6io2+o (ekl” 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

  The intensity at the t 09 0ao 8bvktf0)nkc 9x,z0aurfvya+lhreshold of hearing for the human ear at a frequency of about 1000,0a k0+ a9v kzav0fxby9c8n urf)0lot Hz 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 =   

  A plane is traveling at z 0 o5e3anfmqdgik528*yz1( q;aeljj Mach 2.0. An observer on the ground hears the sonic boom 1.5 min azgq1 (q23alja 5n 0e 8iofjmdye5*;z kfter the plane passes directly overhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedb x-k2nxcd1 z*doat is 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