What is the evidence that soundpvb p9 b7:oe7e travels as a wave?

What is the evidence thai9u p0kh9av7gy0f5n( defi)tj+c hm4wl).tn t sound is a form of energy?

Children sometimes play with a homemade “telephone” by attaching a string to th)r7i hf.jdj- 08;z gheoe +tcue bottoms of two paper cups. When the string is stretched and a child speaks into one cuh7ou +ed0e h-jcjiz.r ) g8f;tp, 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 water, do you expect the frequencyy *( q:;z-rtwgk8xmktgry a): or wavelenygy-mtw:qtza*( k8r;r )k:g x gth to change?

What evidence can you give that the speed ,ahx8rrc)d6tp(fm. v of sound in air does not depend significantly on frequencvdh 8xtfc6 .m,ra)r (py?

The voice of a person who has inhaled helium sounds very high-g0*s5i7q k2qn4jq kmv pitched. Why?

How will the air temperature inq0jfdij3yvw jad +.8. a room affect the pitch of organ pipes?

Explain how a tube might be used as a filter to reduce the amplitude of sounda383+ lct0ek mu ) fgje5ra9jys in various frequency ranges. (An exefmej8 +kg05 uay 9jal3)c3 trample is a car muffler.)

Why are the frets on a guitar (Fig. 1+e 7/yzbp za3t ,mz1yfpsms(,2–30) spaced closer together as you move up the fingerboard toward the/y zsp,,atsbzzf+m3 ymp 1e7 ( bridge?

A noisy truck approaches you from behind a building. Initially you hen4c bd) q4a7zwar 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 on diffraction.] czw)4na7dqb4

Standing waves can be said to be due to “interference in space,” whereas d+k)g d18tmfmbeats can be said t )8d+md1g kmfto be due to “interference in time.” Explain.

In Fig. 12–16, if the frequ8op(z te gnd30ency of the speakers were lowered, would the points D eg 0d(nz38tpo and C (where destructive and constructive interference occur) move farther apart or closer together?

Traditional methods of /g3tn:raer(mo6,zf-9d f j ziprotecting the hearing of people who work in areas with very high noise levels have consisted mainly of efforts to block or reduce noise levels. With a relatively new technology, headphones are woa, en:tgzz-jo irf9d3fm/r( 6rn 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 wave cave +edc)m.7apn be thought of as a superposition of two sound waves with slightly different frequencies, as in Fig. 12–18. In which of the waves, (a) or (b), are the two component frequee+.ea m7)dc pvncies farther apart? Explain.
(12-31)
(12-18)

Is there a Doppler shift if the source and observer move in the same direction,zci:pbi87- nz with the si8n:z p c-7bziame velocity? Explain.

If a wind is blowing, will this alter the frequency of the sound heaij8ebf 6n7 fnqm+p90s rd by a person at rest with respect to the source? Is the wave 6qfn bienjs+f m8709plength or velocity changed?

Figure 12–32 shows various positions of a child in motion on a swing. A 6:e md op;mu ped-3lj6agnr)t4)x;almonitor is blowing a whistle in front of the child on the ground. At which position, A through E, will the child hear the highes3xo;g- d:prej 6plmd)ue)a6t l 4;namt frequency for the sound of the whistle? Explain your reasoning.

  A hiker determines the length of a lake by listsw2xp2 j3pam1ening 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 the leng13j a2wmxpsp2th of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship just below the waterline. He hears pnarf tu20uzvw tn4+c. 5b*m 0the 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 1cu4+0bnrm 5ftu. p0v ntaz*2w560 m/s (Table 12–1) and does not vary significantly with depth.    $ \times10^{ 3}$m

  (a) Calculate the wavelengths in air at hlb6le36ba s 8 ah. x)j/s7myt20 $^{\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 schoo/ m;npi6.iu4pj*u as1m-(wjflb ( *evyfu en2l of tuna on a foggy day. Without warning, an engine backfire occurs on another boat 1.0 km away (F2 l/w.eun4*jb6e1s;mi p*ivua f(-p n(um jf yig. 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 splash it makes when strikiz(/rc8 q qxf f4e .f*-e3ltnvmng the water below is heard 3.5 s later. How high is the clif4m8-/(f qf r3vef.z neqtc l*xf?    m

  A person, with his ear to the ground, sees a huglfy :0(zk aucjt3:7yne stone strike the concrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other ikaucty(zj3 n :70yfl :n the concrete, and they are 1.1 s apart. How far away did the impact occur? See Table 12–1.$\approx$    $ \times10^{2 }$m

  Calculate the percent error made over one mile) c )1epde.esu of distance by the “5-second rule”. 1d) ucepese) for estimating 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 of 120 dB?ive,4m y k0tkqh5r;,00y lxoob11uhs    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 e/x 5r9 1ne(l plmgr6cl8gi8esound whose intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers prod1o*yjj bm(+c 6( ezkvijkt9m)pa+n/g swn: 6duce a sound level of 95 dB when fired simultaneously at a certain place, what will be the sound level if onvzjmn6w/)(a + (n+pj* ks o :y61dbtmgc j9kiely one is exploded? [Hint: Add intensities, not dB’s.]    dB

  A person standing a certain distance from anlwu5;m a6pdt6co 89t pc8gyqbsac9 -9 airplane with four equally noisy jet engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person experience if the captain shut down all but one ecpq68msba6c9o 5d gc8pla-9w9 u;tyt ngine? [Hint: Add intensities, not dB’s.]    dB

  A cassette player is said to have a signal-to-noise ratio of 84 rktmhyzsv*vct.-9fmoz;1l8a) s z58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensities of the signal and the background noise for each device?zz h9ss8;ov*v r.y1 ztc )-4fl8kmmta 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of sound from a person speaking ibba lhsn8k-k/es l zh(8m(o-0n normal conversation. Use Table 12–2. Assume the sound spreads roughly uniformly over a sphere centered on the mhzeb h8 l(k(b-8sol-as/0kn 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 std+yj*zu4i :gqrikes an eardrum 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 amplifie;dzritpt( ( kon8 0bgx88mj /mr B is rated at 40 W. (a) Estimate the sound level in decibels you would expect at a point 3.5 m from a loudspeakernto/td8jmz ibx8g8( m(0pr ;k 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 regx 6rg+q7iud6l:-t jih*k-ny a istered 130 dB when placed 2.8 m in front of a loudspeaker -qjax 6digu+ n :rt*- ihy6l7kon 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 2.0w;b0toq:x+s 9 zj1;vcvw1 ucjz8 qr o( dB. What is the ratio of the amplitudes of two sounds whose levels differ by this amount? [Hint: See +q;9tsvqxojww 1 oz8c 0brvz(:j;1uc Section 11–9.]$\approx$   

  If the amplitude of a sound wave is tripled, (a) by whau839xo0sko o1 vqhg1y3 cmd)q 8hl:bmt factor will the intensity increase? Incrov9 1 g)8xhmkqosuq1 b:83d0oy3l hc mease by a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal displacefn;2f2wbdwrg -v ngs57c )be4ment amplitudes, but one has twice the frequency of the other. What is the ratio of their intensities?74g rbwgcdfn );s enwfv-b522   

  What would be the sound level (in dB) of a sound wave in air that corresponds tobmc kn: ip2((w a displacement amplitude of vibrating air molecules of 0.13 wb2(mkn(p :icmm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level j j n g*y+)mymvre7a;4to seem as loud as a 100-Hz tone that has a 50-dB sound*nj4gyam+ym ) jvre; 7 level? (See Fig. 12–6.)    dB

What are the lowest and highest frequencies b/00syscc1 bi btw +8bthat an ear can detect when the sound level is 30 dB? c00ti+s cb8bsbbw/y1 (See Fig. 12–6.)

  Your auditory system can accommodate a huge range of sound levels. What-4am6wi wg m4y is the ratio of highest to lowestyg 6wmwa44 mi- 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 frequen o+vry9 ,dhof y;l(xs+cy of 440 Hz. The length of the vibrating portion is 32 cm, and it has a mass of 0.35 g. Under what tension must the string be h x9sry+lo ;+yv(do f,placed?    N

  An organ pipe is 112 cm long. What are the fundamental4*zli uxx f/3k and first three audible overtonesu/*ilk43fx xz 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 frequei+lgjsi +/6srw 1 os3qncy would you expect from blowing across the top of an empty soda bottle that is 18 cm deep, if you assumed it was a closed t+s1ilg6so3rs+wj i/ qube?    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-tube pipes spanning the ranvj8 1x(ke 9uxr.qvs ;zge of human hearing (20 Hz to 20 kHz), what would be the range of the lengths 9x.8 xuz ;(vqksjev1r of pipes required? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

  A tight guitar string has a frequency of 540 Hz as its third harmonic.9q-: j yoyq9,, tig slvf8ug,a What will be its fundamental frequency if it is fingered sa j:iqvq ty og9,u l,-g8f9,yat a length of only 60% of its original length?   Hz

  An unfingered guitar 9y4pnw a/xlsd;6ah-a string is 0.73 m long and is tuned to play E above middle C (330 Hz).9; py- ahana6w4 xsl/d
(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 pipe that emits middle C (262 Hz) e 1g9x3v/ dpow st;a+swhen the temperat xptowd31eg;v9as/+sure 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 ta x0 1ksl27ud dpo os6;waj.: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 Example 12–10 should toss v2wt.0s4jn:vlh -he hole be that must be unco 0nstwl.2s:ojs -vvh4vered to 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, 440 Hz, and 616 Hz, b w3 5igun)o c-xcpgizu8h:n 14ut not at any other frequencies in between. (a) Show why thi-h8o ip xc)w:nz i3 unu1gc54gs 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 opennkbk3q8h px* : at both ends. It resonates at two successive harmonics of frequencies 8k 3bnkxhq* p: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 : mpr 6xyss(4z$^{\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 2.14-m-long5 v0awf c4oi2xr*j .ex organ pipe at 20 . xva4oce0r52ji wx*f$^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximately 2.5ef/r wmjf. +ts)9v:b1v9ebc+groct - cm long. It is open to the outside and is closed at the other end by the eardrum. Estimate the frequencies (in the audible range) of the standing waves in the ear canal. What is the relationship of your answer to the informationtjcb/r19re two)mg9v f-fbc ++ sv.:e 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 t3v +voi o3-1ham c;nah.8cxnv o adjust two strings, one of which is sounding 440 Hz. How fv8m+ha3hccno.3-a ovn i ;1 xvar off in frequency is the other string? ±    Hz

  What is the beat frequency if middle g.5shc x32 q qi7 x40( fir8gcknghjv+qy)qt*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 opwjd .ucr 61 sll13jwu4erates 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 simultaneously, estimate the olu.u 3js4lj 16crd1wwperating frequency of brand X.    kHz

  A guitar string produces 4 beats/s when h0-k9ridb11 zhwvd n*al0jgsu9s(- vsounded with a 350-Hz tuning fork and 9 beats/s when sol-0z9rd 1-dgjakvi9 0wh(v*h1sunsb unded with a 355-Hz tuning fork. What is the vibrational frequency of the string? Explain your reasoning.    Hz

  Two violin strings are tuned to the same frequency, 29.p:l *d/ursew 4 Hz. The tension in one string is then decreased by 2.0%. What will be the beat frequency heard when the two strings are wulp. r:/es*dplayed together? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be heard if two id o/cm d-*fj5xoentical flutes each try to play middle C (262 Hz), but one is at 5.*jo x-of5 d/mc0°C and the other at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks, A, B, an10prd sb9d77i. dyh/fc2se qed 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 frequefee.h02 dcdip sb7sdq9/ r1y7ncy 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 19;c16sa ie 0+hw nyyxucct34wvi ,n7p.80 m apart. A person stands 3.00 m from one speaker and 3.50 m from eu 6n7;,1 sn9 ii0twc pxycv+h43wc aythe 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 132 Hz, butiqo 7)) pgnfd9 a piano tuner hears three beats every 2.0 s when they are played together. (a) If one is vibrating at 132 Hz, what must be the frequency of the gf n7)p oqd)i9other ?   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 ai ;8ecgnbmc k(p1gkauin -o1.0r. How many beats per second will be heard? (Assume g0keco.;-1kg (1bn 8nu pcia mT = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain 8nu)lbdbuuw 3ix 9 u+g h)w( va-ltl37aoiw8/ fire engine’s siren is 1550 Hz when at rest. What frequency do you detect if you move wugii83t7/ w3)luo- u dnab +lw( u)a9b vlxw8hith 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 if6(ap grv1cey89;g l-rc0 v8 gq3hqtw h a fire engine whose siren emits at 1550 Hz moves;gv -gvcc ey 89hp6 q3lqar(t1hr80 gw at a speed of 32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift in frequency if 277u y, x jhdlxf j*.6ghjw6cva 2000-Hz source is moving toward you at 15 m/s versus you movwvuj f*d.j7cx, 6 jxyh27h6 lging 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

  Two automobiles are equipped with the same singyx wzk89fd4dxjwy hf16o, 3u,v4z* uvle frequency horn. When one is at rest and the other is moving toward the first at 15 m/s the driver at rest hears a 9,3 , zyx udfj6o*w4wx41kuvh8vdyzfbeat 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 i (jz:ibb(fs(. bicd0and receives them returned from an object moving directly away from it at 25 m/s What is the receiz:ifb . csbd(b (j0i(ived sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed of 5 m/s As it flies, tdvvao 0: kj ayzf8z),(he bat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency does the bat df8vvaza,ky:(j )z0 ohear in the reflected wave?    $ \times10^{4}$ Hz

  In one of the original(;(ewc 5 jhuza Doppler experiments, a tuba was played on a moving flat train car at a frequency of 75 Hz, and a second identical tuba played the same tone while at rest in the railway station. What beat frequency was heard if the train cae aju(5c(z wh;r approached the station at a speed of 10 m/s ?   Hz

  A Doppler flow meter uses ultrasound waves to measure blooad)ycvur 1+o4 d-flow speeds. Suppose the device emits sound at 3.5 MHz, and the c ur+)1adyo4v 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 ue4 e6ldcy-r w /.zq2sysing 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 ofdy 5/mb 3q-hhi frequency 570 Hz. When the wind velocity is 12 m/s from the north, what frequency will observerib-qdh3my 5/hs 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 atb t7)bon pu/4o 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 paok 1kzpv004 2.3 where the speed of sound is 310 m/s (a) What is the angle the shock wa0kzopv1a0p k4ve 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 a planet where the speed d0wo b0kso8k+ exgvlycuc65k s 05 ,i:of sound is only about 35 m/suisw,s:x 0+ c ed5v8co0lo50kk 6ygbk
(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 8b-7+zn48hdo b:paa lnq + hgj3500 m/s strikes the ocean. Determine the shock wave angle it produces phdb gnzjb:a-l8 37na h++oq4
(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 h7d9d66/f7*aqyw ai yjg3 nxx$/theta$ 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 the grouner9*5ui zekf ) wo5 *vnuauz9)d flying fasv*nu*i u5o95k)9aeuz ze)w rfter 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. 12–34. 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 sends 20,000qi lue olrt-;75 ,,r/xpakz sns1kv-ew66ou/-Hz sound pulses downward from the bottom of the boat, and thenkoo6,v,rus-lk 6etl / u 1wxq 5a;s7ip-r/zen 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

  Approximately how many octaves are there in the n4b4ffr/rp:u *osap gk): gehqa5 p4:human audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display called a sewer pipe symph0juix,e5/rip9)7k mm tr+oomony. It consists of many plastic pipes of various lengths, which are/ei 9uxr5o0)km,7ipojt rmm+ 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 fromf)n. whb(gwk*afyezw-- j2m pj- 6 iw( a person makes a sound close to the threshold of human heari(( iaj2.bf-wjm n -gky6whfw*p) zew-ng (0 dB). What will be the sound level of 1000 such mosquitoes?    dB

  What is the resultant sound level when an 82f u64jt.t yl+h-dB sound and an 87-dB sound are heard.y ul4th6t+fj simultaneously?    dB

  The sound level 12.0 m from a loudspeaker, placed in the open, is 105 dB. Whaby8uta8b g3o5j0w1 9. i-ivvc ahl o;tt is the acoustwjgbc 9t3uo oh- a8t.;0 a5vyv1b8ii lic power output (W) of the speaker, assuming it radiates equally in all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 Hz. The power outpo 3myj-d5d;vd ut drops by 10vd- oddj3m;y5 dB at 15 kHz. What is the power output in watts at 15 kHz?    dB

  Workers around jet aircraft typically l+,+tm+bx *7ezwcqdt3g4rk vwear 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 th+*c ,xb+ 3ekgtz+7m wr4vdtqlat 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 communicatio)qyeqoj 9g t/+ns systems, the gain, $\beta$ in decibels is defined as
$\beta$ = 10log($\frac{P_{out}}{P_{in}}$)
where $P_{in}$ is the power input to the system and $P_{out}$ is the power output. A particular stereo amplifier puts out 100 W of power for an input of 1 mW. What is its gain in dB?   dB

  Each string on a violin is tunetzmbi+ --az7 x ;x.nppd 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?
$f_{A}$ =    $\mu_{A}$
$f_{B}$ =    $\mu_{A}$
$f_{C}$ =    $\mu_{A}$

  The A string of a violin is 32 cm long between fixt.i r8qlm5+5 nzii 6vhed points with a fundamental frequency of 440 Hz and a mass per unit lenilhi+m 85qtin z r56v.gth 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 open tube filled wd*d*n rulosd9k 2-5olith 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 resonate with the tuning fork when the distance from the tube opening to the water level is 0.125 m and agaor-u*do 9n*s 5ll dd2kin 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 o +czthao,.s1tsu2 xkco 0bk9.pen at one end and also 75 cm long. How much tension should be in the string if it is to produce resonance (in its fund 9xo 2bt+stsk .hcuz 0c1a,o.kamental mode) with the third harmonic in the tube?    $ \times10^{ 2}$ N

A highway overpass was ovxg*3ki l2xa j:cw4,9j:kh yqbserved to resonate as one 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 0u mmk78 d,krgrange coming from 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 sog7d80 k,murm kurce than the other. What is the frequency of the sound?   Hz

  Two trains emit 424-Hz whistlet0e.*rx y)ugl;lm av(s. One train is stationary. The conductor on the stationary train hears a 3.0-Hz beat frequency when the or0t.ul)(e; xg*vymlather train approaches. What is the speed of the moving train?   m/s

  The frequency of a steam train whistlewd5zquc:-8 jt as it approaches you is 538 Hz. After it puqzt: - 5wj8dcasses you, 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 cars0m; ag5y )h8;1 is;r xpjhosqi just by listening to the difference in pitch of the engine noise between approaching and receding cars. Suppose the sound of a certain car drops by a full octave (frequency halved) as it goes by on the straightaway. How fastxag;siy80hj osr ;qhpm i)1;5 is it going?    m/s

  Two open organ pipes, soundin8lw*53tvw o r fuxb476wb8 yovueiy)9 g together, produce a beat frequency of 11 Hz. The shorter one is 2.40 m long. How byx*8vuiu fvy w748ooebww6t9 r35 )l long is the other?    m

Two loudspeakers are at opposite ends of a railroad car as it moves past a stnt+ bjafd pc2sw5,+c 044qi9 k/s osomationary 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 j/qw 4n, cb+o5 sos90kdtm4 +sp2iaf cis 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 normally about 0.32 m/s what beaq8ttzs kd;*- cs ;mrv4t frequency would you expect if 5.50-MHz ultras;cq-tv* srsmkd ;z84 tound 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 flying towa:phkaexp;ewi;)i ff ra 25c26rd the bat at speed 5 m/s The ;i fpek rwaa p2i5cfeh6x :2;)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

  A bat emits a series of high frequency slfm4f66 -0rgo z oyxi(ound pulses as it approaches a moth. The pulses are r6f4zl go o-xyf m0i(6approximately 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 emitted?    m

The “alpenhorn” (Fig. 12–38) was once used to send signals from one Alpine villsfc2jod2.ls-w uvcn, k,jd3(age 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 blovulfd ks,3- o s,2jc.jw2(cndwn 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.

  Room acoustics for stereo listening can bket3o9bax8 h*0e-r jue compromised by the presence of standing waves, which can cause acoustic “huebaet0r jx8 -k39o*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 standing waves in this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

  A dramatic demonstration, called “singing rods,” involves a long,h(rc h8z *:5 mlgt+vfb 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 rod can be made to “sing,” or emit a clear, lohf b5:l8c+ zmhtg*v(rud, 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 fo0q :+r;zwt0+obckxnu r the human ear at a frequency of about 1000 Hz ou0bckqr z w; n++:0xtis $I_0$ = $1 \times10^{12 } W / m^2$ 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 the sob l;7lkucknz2. *xn;6kg q)opnic boom 1.5 min afterlz67.)ucx n;kgqnk bpo*2;lk the plane passes directly overhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboat is 6+ jzj7vfspe9e p:a8b15 $^{\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