What is the evidence that sound travelsf wgss,z x6)6+mns.hgn7fi l5 as a wave?

What is the evidence that sound is a form of enei4z, e orw:uk5 zjh0u3g*g)zyrgy?

Children sometimes play with a homemade “telephone” dg1irzo8q)jpo 9lisbd. )t / k2s 0nm(by attaching a string to the bottoms of two paper cups. When the string is soob21gs(8l)sktdrm0 q)d .9pn/jz iitretched and a child speaks into one cup, the sound can be heard at the other cup (Fig. 12–29). Explain clearly how the sound wave travels from one cup to the other.

When a sound wave passes xeez n hkv7f1ek2n++8from air into water, do you expect the frequency or wavelength to e e2kh k 1fnx+ev8+nz7change?

What evidence can you give that the speed of sounv,8dt6za3r 3kacspy * wl ,u/ds/8h wsd in air does not depend significantly on l dh8w du3sws,yt8a,c *z vr/pa/s6 k3frequency?

The voice of a person who has inhaled helium sounds very high-pitched.l( :iw*ts3s yq Why?

How will the air temperature in a room affect the pitch ofhi0.m9,k8kxq.fyb8ky l evw- a jm; 8i organ pipes?

Explain how a tube might be used as a filter to reduce o:hc l.ubf:i 2kz70 aothe amplitude of sounds in vari uczl:foo07. ikbah :2ous frequency ranges. (An example is a car muffler.)

Why are the frets on a guitar (Fig. 12–30) spaced clos9n3isp xw3e1ueu t(-:z)p azzer together as you move up the fingerboard toward the bridge?3azu) (1spue3 t -piw :x9zenz

A noisy truck approaches you froaxm;zg,e jj0qr( -eustq)0-lm 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 high-frequency noise. Explain. [Hint: See Section 11–15 oe ) s0j,rltgq z-u(x qe-mj0a;n diffraction.]

Standing waves can be said to be due to “intecf ix,r82+ yxkrference in space,” whereas beats can ber+k ,ixf2x8yc said to be due to “interference in time.” Explain.

In Fig. 12–16, if th; pya1 t7i/hfje frequency of the speakers were lowered, would the points D and C (w7a1 /;i ypfthjhere destructive and constructive interference occur) move farther apart or closer together?

Traditional methods of protecting the hearing of people 5z)yux( p.:ls l(ivrk who work in areas with very high noise levels have consisted mainly of efforts to block or reduce noise levels. With rlk.(sil 5y)v(:z xpua 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?

Consider the two waves shown in Fig. 12–31. Each wahbsdf+ nu71t8ve can be thought of as a superposition of two sound waves with slightly dis7u1 nb+t hf8dfferent 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 source and obsegar wq75fb1o.g3rs u, rver move in the same direction, w.rbu1rg5q 7 3gao,w fsith the same velocity? Explain.

If a wind is blowing, will this al0toc*lf+kf6 czxwyq .r0oh38 ter the frequency of the sound heard by a persc k.rohcx f6w8y03 *qflozt0+on at rest with respect to the source? Is the wavelength or velocity changed?

Figure 12–32 shows various positions of a child in2-ea3 yuo ft 2vvuy1s s)0kb3b motion on a swing. A monitor is u a s3 12vobvfu0e-3k)sb2tyyblowing 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.

  A hiker determines the length of a lak3u(ti, xnpx d g4qg:f2e by listening for the echo of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.0 s after shouting. Estimate tq fi23gut (4gp: ,xdnxhe length of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship just below the waterline. He hears theg 9() lxtyw9ia7akmymr v9p2- 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 seawater is 1560 m/s ag(-79mvmw9itap)r2 ly9k yx (Table 12–1) and does not vary significantly with depth.    $ \times10^{ 3}$m

  (a) Calculate the wavz2gc)7dbfx37lw .w)kz2 sii : sjm3uselengths 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 fogp*a8 q8db5h skd;mhx* gy day. Without warning, an engine backfire occurs on *pq dkhm* 5sdx8b8h; aanother 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 from the top of a cliff. The spl6jyln qbp4s82i3j *blfrm2q7 ash it makes when striking the water below is heard 3.6 q3ji7 q bly84jb p2nrls2*fm5 s later. How high is the cliff?    m

  A person, with his ear to the ground, sees a huge stone p+xm9b p3nn -0*5udvy sidrto4zx m0 bv.te(-strike the concrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other in the concrete, and they are 1.1 s apart. How far away did the impact occur? See Table 1m0tbvd(d n mx -zor -0pn 9+b*5piv3.ytsex4u2–1.$\approx$    $ \times10^{2 }$m

  Calculate the percent error made over one mile of distance by twi y.s2inf5 b/8ga sx/he “5-second rule” for esn/5xy.asbf8i/wgi2 s timating the distance from a lightning strike if the temperature is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity of a sound at the pain level )/i9c)fda kuc1v/s( t ae/prbc9okqm w-0 sh7 of 120 dB?    W/$m^2$Compare it to that of a whisper at 20 dB.    $ \times10^{-10 }$W/$m^2$

  What is the sound level of a sound whose intensity iz. ijxz-f vyg9w-w*h9y m-/xis $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound level of 95 dB when fired simulta0q qc5)l 1 bj2zre7bxhneously at a certain place, what will be th7hzqj x1el)0c2b b 5rqe sound level if only one is exploded? [Hint: Add intensities, not dB’s.]    dB

  A person standing a certain distance jv11 l rzh)deru ul+17from an airplane with four equally noisy jet engines is experiencing a sound level bordering on )uu1 jvh1rl+e1r dz7lpain, 120 dB. What sound level would this person experience if the captain shut down all but one engine? [Hint: Add intensities, not dB’s.]    dB

  A cassette player is is(,ji4y lfo2 said 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 background noise f4if(si,o 2ly jor each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of sound from a pe)sf-sl r1 j92utxy 8obrson speaking in normal conversation. Use Table 12–2. Ass8 ys -btx 1f)9rl2uojsume 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

  A 50-dB sound wave strikes an eardk1so +4b.;bqeur ; mykrum 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 rated at 250 W, while the more modest amk,h )eqjcm8 e4pe*b v+plifier B is rated at 40 W. (a) Estimate the sound level in decibels you would expect at a point 3.5 m from a loudspeak eekhc4 8+pvq ),ejmb*er 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 mete3idhifz4bp q*7 2wjs -r registered 130 dB when placed 2.8 m in front of a loudspeaker on thw7si3 2f4 *bzj-ph diqe 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 differe :mf jknezbx0ot)6 uck /.q11dnce in sound level of 2.0 dB. What is the ratio of the amplitudes of two sounds whose leveq nx1 t/ km)16:.u0zc ejdbokfls differ by this amount? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound wave is tripled, (a) by what factor will the indz2,qe bbl6e6u w:)ee tensity inu6bze:e)6b qee l2dw, crease? Increase by a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal displace(o)hg(r 1/7h.r e i1ggef7zv ur hhvu)ment amplitudes, but one has twice the frequency of the other. What is the ratio of their intensif)uhr)g 7hgh1(ue71i r vze g(v.h/orties?   

  What would be the sound level (in dB) of a sound wrpk br(lu nxoqj 31 zp(4/3lpbee+l -;ave in air that corresponds to a displacement amplitude of vibrating air moleculese31 4r lu(qxjkpep; +-o3 lpbzr b/(nl of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level to seem as loud as a 100-Hz tone* i;bstn:wx6e that has a 506*sx: be tn;iw-dB sound level? (See Fig. 12–6.)    dB

What are the lowest and highest frequencies that an ear can detect when the s h d-l we-wx2lcy(c.6found level is 30 dB? (See F. ewdx-y (l6 fclc-w2hig. 12–6.)

  Your auditory system can accommodate a huge range of sound lewpz5 (p hx6l -exisg)dc.ai5 6e4u e,avels. What is the ratio of highest t cg6ie.uax5 xpwzl6s (5eep i-d), ah4o lowest intensity at
(a) 100 Hz,$ \times10^{ a }$ a =   
(b) 5000 Hz? $ \times10^{ a }$ a =   
(See Fig. 12–6.)

  The A string on a violin has a fundamental frequency of 440 Hz. Thfl42ksu3tg (2 p9vas he length of the vibrating portion is 32 cm, and it has a mass of 0.35 g. Undess423( uvhfakptlg92 r what tension must the string be placed?    N

  An organ pipe is 112 cm long.r k akb1no+q; cz2ov+p /ah9+//mrwkf n)jy,t What are the fundamental and first three audible overtones if tha +/qaw+,kc;ny mo rkb+jzn)f v/19 2oh/tprke 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 fre1l,tv 3qy1ejx3 d o5ccpt 7.epquency would you expect from blowing across the top of an empty soda bottle that is 18 cm deep, if you assumed it was a clo3.1 7plovcdpxt y3e 1jtcq5e,sed tube?    Hz (b) How would that change if it was one-third full of soda?   Hz

  If you were to build a pipe organ with open-o s hpxwk dc62r.zoku*:,2+qhtube pipes spanning the range of human hearing (20 Hz to 20 kHz), what would be the range of the lengths of pipe:k*h. qhopzodwu 22cs, x6 k+rs required? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

  A tight guitar string has a frequency of 5402p,ksaxbhhgj.w;0c /y 99 i kh Hz as its third harmonic. What will be its fundamental frequency if it is fingered at a length of onlyh2;.jhihxg bcw/ akp 9y,9s k0 60% of its original length?   Hz

  An unfingered guitar string is 0.73 m long andgokwn4+sjnt jo//v.1v)* bsm is tuned to play E above middle C (330ows)g +vjnk vot/./1 4nms*bj 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 organ pip4wajikx0 , 7rae that emits middle C (262 Hz) when tw ,jxai704kra he temperature 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 ap1r: de9x1bno97t/rn l)a rv gt 20 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece y+(8pewd2m: i o*rpkvq7 p1uhof the flute in Example 12–10 should the hole be that must be uncovered ye8mhirw*7poq+v1dup 2: p( kto play D above middle 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 at 264 Hz, 4wty0idn/rh i(88-t a d40 Hz, and 616 Hz, but not at any other frequencies in between. (a) Show why this is an open ord/tr wnh ydi-a(0i 8t8 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 bothgg n;tnkpocn8 p49f1i 6 kbg-h54 jl0w ends. It resonates at two successive harmonics of frequencies 275 Hz c4pn;n-0gjk98 pfh45 b1ongi twl k6gand 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 w +ttad,dcr(/gld1c a i0-.a b$^{\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 audlvcgpg, q:c79 ible range for a 2.14-m-long organ pipe at 2:9 cgq,7cl gvp0 $^{\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+qm h.fn kwm/mvg); p/ to the outside and is closed at the other end by the eardrum. Estimate the frequencies (in the audible range) of the standing waves in the ear canal. What is the relationship of your answer to thnw.kp)mgmfq/v +/hm; e 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 trying to adjust two c070m suyb5 hgstrings, one of which is sounding 440 Hz. How far00ch bum7gys5 off in frequency is the other string? ±    Hz

  What is the beat frequency i:ie j kn7nxecso;;(7af 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

  A certain dog whistle operates at 23.5 kHz, while r )2t8;sgyg 7i(jvulfo5/jvwanother (brand X) operates at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whine of gig8jur;s vj2v5t /(o7y)wfl frequency 5000 Hz occurs when they are played simultaneously, estimate the operating frequency of brand X.    kHz

  A guitar string produces 4 beats/s when sound j:(70eop glbred with a 350-Hz tuning fork and 9 beats/s when sounded wit:o(7pb le0 jrgh a 355-Hz tuning fork. What is the vibrational frequency of the string? Explain your reasoning.    Hz

  Two violin strings are tuned tlju ,s tb34: bvkm(7yyo the same frequency, 294 Hz. The tension in one string is then decreased by 2.0%. What will be the beat frequencbj,u7 tl m4ys (vk:3byy heard when the two strings are played together? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be heard iukd+scamcrb6 ,, 0mi qs,c 6(xf two identical flutes each try to play middle C (262 Hz), but one is at 5.0°C anad0,,sb(ccrcq6,kmu 6 im+sx d the other at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks, A, B, andh1w(0vh pj))rus-zyp 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 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 h(0y 1urzh)pw vs)-pjtogether?$f_A$ =    Hz or    Hz
$f_C$ =    Hz or    Hz
|$f_A$-$f_C$|    Hz or    Hz

  Two loudspeakers are 1.80 m apart. A person stanth23b1(b d oa) 3hwfkyds 3.00 m from one speaker and 3.50 m from )( bf k2h3oya1bhdw 3tthe other.
(a) What is the lowest frequency at which destructive interference will occur at this point? f =    Hz
(b) Calculate two other frequencies that also result in destructive interference at this point (give the next two highest). Let T = 20 $^{\circ} $C $\approx$    Hz $\approx$    Hz

  Two piano strings are supposed to be vibrating at 1 g: to sk3 ak,,mm;kt9vtisq)532 Hz, but a piano tuner hears three beats every 2.0 s when they are played together. (a) If one is vibrating at 1i3mtkvgkattq;s,9s5o,km :) 32 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/xdrmb5, syc 4.76 m in air. How many beats per second will be hearsc x/rd,b y45md? (Assume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain fire engine’s siren is 1550 v8.jken;5 3nox hu*bsHz when at rest. What frequejon.n vx3s uh5b8;* kency do you detect if you move with a speed of 30 m/s
(a) toward the fire engine,    Hz
(b) away from it?   Hz

  You are standing still. What frequency do you detect if a fire enginta0tk;s9jp8(b /nqw q nd lm-;e whose siren emits at 1550 Hz moves at a speedm- k;0anljwd/8qs9(tpqn b t; of 32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift in frequency if o5me zve2(5vr a 2000-Hz source is moving toward you at 15 m/s versus you moving toward it at 15 m/s Are the two frequen5e ro 5m2ezv(vcies 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 w l9x,t. 8fesyzith the same single frequency horn. When one is at rest9xf8z.l, eyst and the other is 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 07btend a3j3e kHz and receives them returned from an object moving directly awe3en d07abj t3ay from it at 25 m/s What is the received sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wae oucjt+0d5vn4 x.tu5hf8ub g92s 7kcll at a speed of 5 m/s As it flies, the bat emits an ultrasontsb5 n48h0+ 2ctuejkg5xvc 9do.uu7fic sound wave with frequency 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 played on a moving flat ip ucb) 2-f*/e:1 fmg som3mw)qg -beetrain car at a frequency of 75 Hz, and a second identical tuba played the same tone while at rest 3qe megbswu ofm1 /-g*if :-))bep2m cin 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 ultrasound waves to measure7f mm 4vev69md blood-flow speeds. Suppose the deviv7v946fmm md ece emits sound at 3.5 MHz, and the speed of sound in human tissue is taken to be 1540 m/s What is the expected beat frequency if blood is flowing in large leg arteries at 2 cm/s directly away from the sound source?   Hz

  The Doppler effect using ultrasonic wavj qo,t5mj jderwm1v0 y, t7)r.es 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 57xtz -kyk7 t(7k m;f1me0 Hz. When the wind velocity is 12 m/s from the north, what frequency will observers hear who are located, at rt;xem 7kk y (k-z71tmfest,
(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 objectm1)aa3w)t(ux(dn) jmsvsy,afc(k hd a1y 46f moving on land if its speed 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

  An airplane travels at Mach 2.3 where the svj- ijfq7k-g*peed of sound is 310 m/s (a) What is the angle the shock wave makes with the direction g-f-j*kjq7v i 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 a planet9+/ g ovpq6m2iz4s hjo where the speed of sound is only about 35j9o 4 z qim6hpg+vo2s/ 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 ocean. Determine t+a 3lycr -fp5sx6k,1bbwa j 0she shock wave angle6b1kjc-l b s swp5f0+ayx ,ra3 it 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 lt:f9gq2n5;8l, a/ l nhwrqsh$/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly overhead and see a plane exactly 1.5 km above t(p fe;q(ub z)fhe ground flying faster than the speed of sound. By the time you hear the sonic boom, the plane has traveled a horizontal distance of 2.0 km. See Fig. 12–p;)((fzu be qf34. 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 sends 20,000-Hz sound pulses downwa oxkg l8ov5,-.3q nyd- jgqi.p.lxum/ rd 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 (in fresh water)? / - 8,vqinxkljoqy. xdgg-mo..l p5u 3   s

  Approximately how many octaves are there in the human audible rangvu ,a f-tfwdc-;i.0kq7 1j nsie? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display called a sewer -fy+ 7b 0djtyekv4h8w zm:9rf pipe symphony. It consists of many plastic pipey7tkw94fyz +8 -0ejvhbmrf: ds 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 a personkp*oow mua r24 :9(o4 xasw8bx makes a sound close to the threshold of human hearing (0 dB). What will be the sound level of 1000 such kp 48 ao24*ao(xmwouwbxr:s9 mosquitoes?    dB

  What is the resultant sound level when a t l9i:pr(xb1 tgz5nn.n 82-dB sound and an 87-dB sound are heard simub5(:l ntz9 .tp1r gixnltaneously?    dB

  The sound level 12.0 um (b8oj-xj;rm from a loudspeaker, placed in the open, is 105 dB. What is the acoustic power output (W) ofb(;um jrxj- 8o the speaker, assuming it radiates equally in all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 Hz. The power outpu-+h y0u (+cahdla aqh0 ks30y*jgohu6t drops by 10 dB at 15 kHz. What is the powe h6+ah3jq ga+*k0da0ul y ho chu0(-ysr output in watts at 15 kHz?    dB

  Workers around jet aircraft typically wear protective devices over their earsdo6cq n. j1 h4jmjnk*5. 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 *ojcqn 5j6mn4 j.d1hkthe power intercepted by an unprotected ear at a distance of 30 m from a jet airplane engine?    W

  In audio and communications syst6mwp jhq u ae f8q28.3j3e/erlems, 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

  Each string on a violin is tuned to a frequency 0n*d7d l ufd:h2:1pnjp 5nfqz9nay +a1$\frac{1}{2}$ 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 is 32 cm long bjo6+a5rrb( ki- hps /cetween fixed points with a fundamental frequency of 440 Hz and a mass per unit length ba56-s/p krj( ihcr+ oof $6.1 \times10^{-4 }$ 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 d)nor5 nbg7b :io(l(v into vibration above a vertical open tube filled with water (Fig. 12–35). The water level is allowed to drop slowly. As it does so, the airln ib() :ng57dbovr(o 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 st/ xr,e o+hdq7.;7 emuqqpg5n jring of mass 2.10 g is near a tube that is open at one end and also 75 cm long. How much tension should be in the string if it is to produce resonance (in its fundamental mode) with the d/en5oj;r. 7 e,xhq7mq+ qgputhird harmonic in the tube?    $ \times10^{ 2}$ N

A highway overpass was observed to resonate as on,ff rbxjpc6a 03pgfa v09 l+k82h z.mze full 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 coming frh1s7phq)ya zy74eqlys6n) p3om 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 the frequency of thhp1qln7y6)y )h zpa y47s sq3ee sound?   Hz

  Two trains emit 424-Hz whistles. One train is stationary. The cc emr1kg;tu6 x6.znbir7 y-b0 onductor on the stationary train hears a 3.0-Hz beat frequency when the other train approaches. What is the speed of the moviug; ntm-b1b yk.rxr ze76 ci60ng train?   m/s

  The frequency of a steam train d-e:6(en1-xmrxhc e8) bo lb rwhistle as it approaches you is 538 Hz. After it passes you, its fr:) hc6bee(- xore 8 ldn1rm-bxequency 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 the d yrk;z)ev.3/h ct3tpqifference in pitch of the engine noise between approaching and receding cars. Suppose the sound of a certain car drops by a full octave (frequency halved) as it goes bypkt q;zev3 hctr y/).3 on the straightaway. How fast is it going?    m/s

  Two open organ pipes, sounding together, pr*p0 gae56blc coduce a beat frequency of 11 Hz. The shorter one is 2.40c aeg*c pb50l6 m long. How long is the other?    m

Two loudspeakers are 6u8 )mu3zu iw so-a*afat opposite ends of a railroad car as it moves past a stationary observer at 10 m/s as shown in Fig. 12–37. If the speakers have identical sound frequencies of 212 Hz, what is the beat frequency heard by 6iu)a 3 -z*8suaf uwmothe observer when (a) he listens from the position A, in front of the car, (b) he is between the speakers, at B, and (c) he hears the speakers after they have passed him, at C?

  If the velocity of blood flow in the aorta is no2/;cz:cwp8jzbwi d5 brmally about 0.32 m/s what beat frequency would you expect if 5.50-MHz ultrasoun bz2; jdz/cw bci5:pw8d waves were directed 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 speed 6.5 m/s while the moth is fl 8)b (v6ajewe blml/w8ying toward the bat at speed 5 m/s The bat emits a sound wave of 51.35 kHz. What is the frequency of the wave detected j 6mb w8 wl8e/)la(ebvby the bat after that wave reflects off the moth?    kHz

  A bat emits a series of high frequency sound pulses as it3k1 .jpzfe0cd 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 next chirp is em.pe ck0j3 d1zfitted?    m

The “alpenhorn” (Fig. )ckib ,wb3afq k)g8.e12–38) was once used to send signals from one Alpine village to another. Since lower frequency sounds are less susceptible to intensity loss, long horns were used to create deep sounds. When played as a musical instrument, the alpenhorn must be blown in such a way that only one of the overtones is resonating. The most popular alpenhorn is about 3.4 m long, and it is called the F sharp (or G flat) 3q bwab k.e)8 ikgf)c,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.

  Room acoustics for stereo listening can be compromised by the presence of stand r;;rizx-frb( ing 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 frbr ;-iz ;(rxfrequencies for the standing waves in this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

  A dramatic demonstration, called “sii/we 5;ynasyt - 95f7dma+rv pnging rods,” involves a long, slender aluminum rod held in the hand near the rod’s midpoint. The rod is stroked with the other hand. With a little practice, the vaias5/d7efw -;n 9rm+ 5t yyprod 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

  The intensity at the threshold of hearing for t e.b,wox,6com he human ear at a frequency of about 1000 Hz6 eo, ,cxwb.mo 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 Mach 2.0. An observer on the ground hears the1*la7a*aso azf/ h 03cv5axhl sonic boom 1.5 min after the plane passes directly overhead. What 0sx fa/ av*hh1oa3 aa7*zl5lcis the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboat is kyo60x :vx +hv9nxvb715 $^{\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