What is the evidence that sound prd k9 wyfb0l9 o5y:*htravels as a wave?

What is the evidence that hp. c 9; i;jncmz/u9,pcj erz1sound is a form of energy?

Children sometimes play with a homemaddyx woxdd 70hs/b (geim082q4e “telephone” by attaching a string to the bottoms of two paper cups. When the striow07 4ixeym/hdg (d280dqsx b ng is stretched and a child speaks into one cup, the sound can be heard at the other cup (Fig. 12–29). Explain clearly how the sound wave travels from one cup to the other.

When a sound wave passes 2vku1 uqxw-zb+1r;m dd rm*1qfrom air into water, do you expect the frequency or wavelen*rw1d mvr1qu zdu-;q21xk m b+gth to change?

What evidence can you give that the(8+xjay9q3 (ns j /7gei smtgv speed of sound in air does not depend significantly on fv x/ nai(sge87tj+sy(j 9q mg3requency?

The voice of a person who has inhaled helium sounds ver8xmf8c+cn n) ee 5c3bey high-pitched. Why?

How will the air temperature in a room affect the pitch of organ pipesso )bhfudq)i+r5 r5wt -5 m1+emqlo(s?

Explain how a tube might be used as a filter to reduce the amplitude of sounds i0dpfd 1hg26jgmp n 4+dn various frequency ranges. (An example is a g16m4pdg0hp j2 n+ddf car muffler.)

Why are the frets on a guitar (Fig. 12–30) spaced pqjt,.x s8a*6 ob1obd closer together as you move up the fingerbpod ba .jq,so61 *8xbtoard toward the bridge?

A noisy truck approaches you from behind a building. Iniq wtg/y9(7h mitially 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 Sectg9 tm7q/hy i(wion 11–15 on diffraction.]

Standing waves can be said to be due to “interference in space,” whereas beats1qro.n e a*o7u 7azv2s can be said to be due to “interference in time1sao2au 7.eo v* rzq7n.” Explain.

In Fig. 12–16, if the frequency of the speakers were lowered, would *:f8 wyn6zdirz )r w7athe points D and C (where destructive and constructive interference o n)w6zy7: *zirraw8f dccur) move farther apart or closer together?

Traditional methods of protecting the hearing of people who worqiz4-d(r pm 7w +bqev7. 4ljmak 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 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 qq w +7(jmepia.-4blz4 7mrdv the ears?

Consider the two waves s3 :0usqy id88vguam2shown in Fig. 12–31. Each wave can 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), y2auqi:g3 v ds80 ums8are the two component frequencies farther apart? Explain.
(12-31)
(12-18)

Is there a Doppler shift if the source and observer move in the same direc-gjv/xx0/-21n z mog:ecd e k *w0jlaption, wil- cj 2ov -/zewgkp0x: d/xe*1j0amgn th the same velocity? Explain.

If a wind is blowing, will this alter the frequency9j cak 98wl y z4-fycyur8x93aa:ak,l of the sound heard by a person at rest with respect to the source? Is the wavelength or velocity chan9 kyaw9ac ay9,ya4lrk-z8 c l3:xfuj 8ged?

Figure 12–32 shows various positions of a child in motion on a swing. A mksn *0zds + kekfi9y- z+ j1fr)*k0nhkonitor is blowing a whistle in front of the child on the ground. At which position, A through E, will the child hear the highest frequency for the sound of the whistle? Explain your reasdkk* +z+9)n kffhyrj1szik* 00-eskn oning.

  A hiker determines the length of a lake by listening for the ec5 kph89znvp5l ho of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.0 ph nkzl95p58v s after shouting. Estimate the length of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship justyeyii g(5./ vp bddn/7 below the waterline. He hears the echo of the sound reflected from the ocean floor directly below 2.5 s laterdyiy7ng.ei5vd ( bp// . How deep is the ocean at this point? Assume the speed of sound in seawater is 1560 m/s (Table 12–1) and does not vary significantly with depth.    $ \times10^{ 3}$m

  (a) Calculate the wavelengths in air at 7cnb5vys*g 5 l20 $^{\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 drif*vdvitkp .gibl-( ),yting just above a school of tuna on a foggy day. Without warning, an engine backfire occurs on anoth)igiyp( ,-. t klv*dvber 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 splash it makes when striking tha8mo/ rq bfmj p.3;t1ne water below is hea 3/porm .qj8tf1a;nb mrd 3.5 s later. How high is the cliff?    m

  A person, with his ear to the ground, se3b apd l+1z k .kjp0gfff6co12es a huge stone strike the concrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other in the concrete, and they are 1.1 s apart. How far awayop 6lf f1 cagz1kbf.j0pd3k2+ did the impact occur? See Table 12–1.$\approx$    $ \times10^{2 }$m

  Calculate the percent error made over o. 1juvm l- w.om+v *xyk q:67qoqgda0hne mile of distance by the “5-second rule” for estimating the0m1.w6 qvmky-dv og*ao :.luqqx7jh + 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 ldyv ib01bo)v7 evel 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 whoseg;dyili0k x26ind. m- intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound level of 95 dB when fired simultaneouslyjs / 3wobcf++3zfbp kh243tup at a certain place, what will be the sound level if only one is exploded? [Hint: Add inten o cb3jf2b+fzskhp p3+u3w/t4 sities, not dB’s.]    dB

  A person standing a certain .-u tqcracz64nfu*/yje65px distance from an 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 engine? [Hint: Addp 6-*jru5tyuf /xe zq6c.c4na intensities, not dB’s.]    dB

  A cassette player is said to have a signal-to-noise iy1uf0c1i 3ib2)2dee6 agt ohratio of 58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensu ba i de 0i)g2h631et2yicf1oities of the signal and the background noise for each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of s) pul8(;asu(.,ifv vllj 8smp ound from a person speaking in normal conversation. Use Table 12–2. Assume the sound spreads roughly uniformly over a sphl.)vulf mv 8u;( lji8p (sa,psere 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 eardrum ye/g t;js04x,s; s8svomhb6 t 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 c 2dewm )1kr(lmore modest amplifier B is rated at 40 W. (a) Estimate the sound level in decibels you would expect at a point 3.5 m from a l 1ldkm2) crew(oudspeaker 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 regoz0vwej3fu fj.76gq 5istered 130 dB when placed 2.8 m in front of a loudspeaker ongv3uz0 5j.w of f6e7jq 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 typica7-p- zu d+luwwtgb/l,lly detect a difference in sound level of 2.0 dB. What is the ratio of the amplitudes of two sounds whose level+w, 7g/ub ptw dzu-l-ls differ by this amount? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound k f i9d;ifqkev,- il.am 3uz:gc; e6zt4 c(zz:wave is tripled, (a) by what factor will the intensity increase? Increasefi,z(qg.zz m6 i:ke;4kcdte93ic -vulz: f a; by a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal displacement amplitudes, but one has twicegi c4 v8voh8-+zrz*br the frequency of the other. What is the ratio of their intensitiesi88v*br-zzgcr vh4 o+?   

  What would be the sound :t8 xijw0+d ,7ve(a2qiy p;*h6uwmw yhwfmw 4level (in dB) of a sound wave in air that corresponds to a displaceme,wmw 7w;8v+hyda:2u ept wmyix q*fhj0wi64( nt amplitude of vibrating air molecules of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level to seem as loud as a 100-Hzq ( u8kkgi30qq u-/ook9e1 mhy tone that has a 50-dB sound level? (See Fko-y1 q i/k0qu3h(m98qu oeg kig. 12–6.)    dB

What are the lowest and highest frequencies that an ear can detect when the soup;7+l0hh r 6zg1sz2x jziw5fpnd level is 30 dB? (See Fig. 12–6.) hg 0; ij1r z7z+2fswx6p5lhpz

  Your auditory system can accommodate a huge range of soun**,mpawly1z p.y /dlud levels. What is the ratio ulpm*,ya1.ywz *pld/ of highest to 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. 6uh9-mcr 1tybr-zo sxeab, 0rz/v,8gThe length of the vibrating portion is 32 cm, and it has a mass of 0.35 g. Under what tension must the string be pz,gbub/ror9xe0y61h- 8 r z t,-cs mavlaced?    N

  An organ pipe is 112 cm long. What are the oh6apjektxc ; 5i(8j6 fundamental and first three audible overtones if theta; p(kc8jj6 5 xeoh6i 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 frequencya (5ey./s+7g/l bjfl 7zvktw t would you expect from blowing across the top of an empty soda bottle that is 18 cm deep, if you assumed it waj 5yef wtt/l7. bv7l zgs/(+kas a closed tube?    Hz (b) How would that change if it was one-third full of soda?   Hz

  If you were to build a pipe ormmyzu8bkn(ny n ,np3l7c)r 2)6hl ip 2gan with open-tube pipes spanning the range of human hearing (20 Hz to 20 kHz), whatpl)z )nb2(i 3k7mmynnr,cl8uy 2p nh6 would 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 k1t0zu + jq 25-xb:ev jm,++cpfsv cje6vv3lhHz as its third harmonic. What will be its fundamental frequency if it is fingered at a length of only+v,qe +h 3 -6jkcm 0e5vfzp2utvxbsj l:c+1jv 60% of its original length?   Hz

  An unfingered guitar * druydu3j+70nsh; ihstring is 0.73 m long and is tuned to play E above middle C (33hu;7+3 0dyurj*i nh ds0 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 pipe that emitsqt9tl hupt7 6sx+j,e 33*a 6zxpe2hlw middle C (262 Hz) when the temperature iszx s6,ut7 hpw*tlhe632+tpxq 93jl e a 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, 3+6uusyj3jc a*pd hc0 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece of the (s9a kg*cr s)(,tiwzdflute in Example 12–10 should the hole be that must be uncovered to pla *, (()ridsztawkgc9 sy 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, 44 ,/y woknvx5,r0 Hz, and 616 Hz, but not at any other frequencies in between. (a) Show why this is an vxrw ny/o k5,,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 lmj xut1+6eg/9fgc7 c ut9)fnx9v -qwqong is open at both ends. It resonates at two successive ha 6t9x1w 9gu79 -ugme ffqtn+jqv/c cx)rmonics of frequencies 275 Hz and 330 Hz. What is
(a) the fundamental frequency,    Hz
(b) the speed of sound in the gas in the tube?$\approx$    $ \times10^{2 }$ m/s

  A pipe in air at 20 uhn(y (()yze5j i,kkr $^{\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- . h2t3qnbwc:7niftt /m-long organ pipe 7qtbwcn. 3f th2 t/n:iat 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximately 2.5 0s iep rvli14be94 xjpo( l8g;yv,d+zcm long. It is open to the outside and is cloopz1 ljpe xb 9+ 8;idg(yv4v4se,l0rised 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 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.;c-iencp al2n5a5u+ xp.qu e+0 s when trying to adjust two strings, one of which is sounding 440 Hz. How far off in 5 lp;cne-uei+nc uq.pxa2a5+frequency is the other string? ±    Hz

  What is the beat frequency if middle C (262 Hz) - h1h0cxc*kmi 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 another (brandgr4n. 7fe4fz*)esk n t;*kyvo 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 operating fresko*tvz7)nngkye * r fe;44f.quency of brand X.    kHz

  A guitar string produces 4 beatj8n50 v5 :*dwc.u)8n2w xiusq anv gqds/s when sounded with a 350-Hz tuning fork and 9 beats/s when sounded with a 355-Hz s ug5u5jdna :.2cvwdq wxv8*80i)n nq tuning fork. What is the vibrational frequency of the string? Explain your reasoning.    Hz

  Two violin strings are tuned to the same frequen-2fhklt g- zx4pc/q5zcy, 294 Hz. The tension in one string is then decreased by 2.0%. What will be the beat frequency heard when the two strqc-tz x-5 lh/zpf4k2g ings are played together? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be dbsu)80m v2tp heard if two identical flutes each try to play middle C (262 Hz), but one is at 5.0°C and the othtsp2bd0um8 v) er at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks, A, B, and C. Fork B hy7su2pxf 55/ kuo0a ecp1n5bx5g k fp.as 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 p5 fxy/7.op5 1ngp5fesc bu520 u kxkafrequencies 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. A person stands 3.00 m from oxtjd+ (/godll7 q( wp+ne speaker and 3.50 m from the +d t /+o g7px(qwld(ljother.
(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 H 7t/r/jtein2up 4i9zceym p5 )z, but a piano tuner hears three beats every 2.0 s when they are played together. (a) If one is vibrating at 132 pm/ n zjcye274t/ieuirt)59pHz, 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 yof5+y1yuo*x 8u1z eg m in air. How many beats per f zouu *1yy 1e5+ygox8second will be heard? (Assume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain fire engine’s siren is 1550 Hz when at:(f ko+uxc./jui -zr f rest. What fr/u+f-k. :uz(ofjr ix cequency 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 d fn 9*su:dhq0ys/xe;yetect if a fire engine whose siren emits at 15 yx:90nqu;*/hd yfe ss50 Hz moves at a speed of 32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shif67+qm2zq wg mtt gc ht6(s,(xvt in frequency if a 2000-Hz source is moving toward you at 15 m/s versus you moving toward it at 15 m/s Are the two frequencies exac7q thzg x26s,mc (mvwg6t(tq+tly 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 3.cc* rcty cxh*i4:mdequipped with the same single 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 beat frequency of 5.5 Hz. What is the frequency tc*.xcc tdyh: 3*ricm4he horns emit? Assume T = 20 $^{\circ} $C    Hz

  A bat at rest sends out ultrasonic sound waves at /:h xlgkm v2h1;paw*dat/nr -s ar0,h50.0 kHz and receives them returned from an object moving directll*: / x-rpdhnhhwr a/mk; 0tv1g2,saa y away from it at 25 m/s What is the received sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed z1ytmpt.2l3- t(rw t/c r*hnl, nsqy) of 5 m/s As it flies, the bat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency does the bat hear in the reflected wavs )t mrtrq t3.zh*yc1,nl2wp /t l-ny(e?    $ \times10^{4}$ Hz

  In one of the original Doppler experiments, a tuba was played on a movins *u7cm6,8mm mga er)a(,yn jlg flat train car at a frequency of 75 Hz, and a seconse* aca, mm6jgmrumln(y,8 7)d identical tuba played the same tone while at rest in the railway station. What beat frequency was heard if the train car approached the station at a speed of 10 m/s ?   Hz

  A Doppler flow meter uses ultrasound waves to mr,g5 cc x2lart40e hy(easure blood-flow speeds. Suppose the device emits sound at 3.5 MHz, and the speed of sound in human tissue is taken to be 1540 m/s What is the expected beat frequency if blood is flowing in large leg arteries at y ce l,2x0ahr(cr45tg 2 cm/s directly away from the sound source?   Hz

  The Doppler effect using ultrasq5dnafc h7h0i ch7)yh:q3 4qzonic 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 4tu6yv c3vzx*14 zrjkgkve( 0the wind velocity is 12 m/s from the north, what frequency will observers hear who are locateuvkkxvz1tc643 (erv *zj 04ygd, 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 speedw1l(j lq1 6v*pyel47vi r4 cc* vmvjh( 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 vsu9t/lp15r z7 nd-l7 byo vv;2.3 where the speed of sound is 310 m/s (a) What is the angle th9v7z/p dlvl-;1t b r7uy5 vsnoe 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 a planet where tr zy-:ac(fm, rhe speed of sound is only abr:r-cz(,a fm yout 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 thhe9te )+ guutxyp 4l0+e ocean. Determine the shock wave angle it produces tgu0t+x )luh p 4+9yee
(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 a,2jk -jbphupsze9)e/l r ,v0$/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly ovlff.9 s)e piu2g2wy.werhead and see a plane exactly 1.5 km above the ground flying faster than the speed o9l2pi uf) .fye2ww .gsf 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 20,000-Hz sound pulsesjzkt9 cf2g-e,kfngqmzg12 9v nw4..d downward from the bottom of the boat, and then detects echoes. If the maximum depth for which it is designed to work is 200 m, wg4v -9mk9 1fcen2 nzd.kgqzj2,fw.gt hat is the minimum time between pulses (in fresh water)?    s

  Approximately how many octav+ opg x7r,/k+o4+qu2tr1wek fh a paa1es are there in the human audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display called a sew/a l7,qg tmrip41x6xper pipe symphony. It consists of many plastic pipes of various lengths, whi/ ligq 71, atp6m4xpxrch 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 froesyxg401vy pps2: 9ejm a person makes a sound close to the threshold of human hearing (0 dB). What will be the sound level of 1000 such24y 01vee y: psxgj9ps mosquitoes?    dB

  What is the resultant sound level when an 82-dB sound and an 87-dB soq0oo cr ; .vqpijwvi;.fw-n14und are heard si vqcj..0wipro1-n qwo fiv; 4;multaneously?    dB

  The sound level 12.0 m from a loudspeaker, r- jrwc--bp/xybb r3 .placed in the open, is 105 dB. What is the acoustic power output (W) of the speaker, assuming it radiat w-x-cpbjy/ rbrbr-.3es equally in all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 Hz. Tw48a ws5,qgin m ay.l6he power output drops by 10 dB at 15 kHz. What is the power output in syl w5a.6ngi m8qa4 ,wwatts at 15 kHz?    dB

  Workers around jet aircraft t pappfu (9j:g(ypically wear protective devices over their ears. Ajf( p9gp:(u passume that the sound level of a jet airplane engine, at a distance of 30 m, is 140 dB, and that the average human ear has an effective radius of 2.0 cm. What would be the power intercepted by an unprotected ear at a distance of 30 m from a jet airplane engine?    W

  In audio and communications systexiq7,-c9nnvim0ot , lms, 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 tuxup/ 5v,c 8ywus5,mpaz khh:7ned 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 fixed points widfy-ksm(dn2)jr pf0 *th a fundamental frequency of 440 Hp 0d*jynr-m 2f(sk )fdz and a mass per unit length of $6.1 \times10^{-4 }$ kg/m
(a) What are the wave speed and tension in the string?    $ \times10^{2 }$ m/s    N
(b) What is the length of the tube of a simple wind instrument (say, an organ pipe) closed at one end whose fundamental is also 440 Hz if the speed of sound is in air?    m
(c) What is the frequency of the first overtone of each instrument?   Hz    Hz

  A tuning fork is set into vibration above a vertical open tube ft96+5vfeb 3azr- lz-:w o/csdox nwm)illed with 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 xbr s l/-)zvom-+c zww53n6ode9fa:t 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 gw8ue.i 5p7xtu1 :agqk is near a tube that is open at one end and also 75 cm lonpwu tk 1eag5quix: .87g. How much tension should be in the string if it is to produce resonance (in its fundamental mode) with the third harmonic in the tube?    $ \times10^{ 2}$ N

A highway overpass was observed to resonate as one full c) 3gauphhkkklbg/-1 9f)--g0tun qt 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 ranizpk-ku 9:th.(e g1sq ge 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 o.zqgh(-k1 u9p : tskiene source than the other. What is the frequency of the sound?   Hz

  Two trains emit 424-Hz whistles. One train is stationary. The conductor 86x0)u g-nwf hh/iqvn on the stationary train hears ax6vwqgn hu/n-h 08i)f 3.0-Hz beat frequency when the other train approaches. What is the speed of the moving train?   m/s

  The frequency of a steam train whistle as it approaches yoummrmj5u*m:+di 1thi x*mi *gx4h z -9l is 538 Hz. After it passes you, its frequency is measured as 486 Hz. How fast was the train mov1*rm9-d lx5:*4h imuzxt mjmi*mg+ihing (assume constant velocity)?    m/s

  At a race track, you can estimate the speed w , p5nk(1wmvyof cars just by listening to the difference in pitch of the engine noise between approaching and receding cars. Suppose the sound of a certain car drops by a full octave (frequency halved) as it goes by on the straightaway. How fast is it gowvn51ypw,(km ing?    m/s

  Two open organ pipes, sounding together, produce a beat frequency of 11 Hz hoe5qw+84 +wp kp0ygk. The shorter one is 2.40 m long. How long is the otheq+ +yk phpk0wgo58w e4r?    m

Two loudspeakers are at opposite ends of a railroad car as h 3-mnsmf8*4i(mdpkt it moves past a stationary observer at 10 m/s as shown in Fig. 12–37. If the speakers have identical sound frequencies of 212 Hz, what is the beat frequency heard by the observer when (a) he listens from the position A, in front of the car, (b) he is between the speakers, at B, and (c) he hear-n*m m3 (ms hpidft48ks the speakers after they have passed him, at C?

  If the velocity of blood flow in the aorta is normally h8.xoq+t n uigy5b)x:+36eaa 7k gspmr h65ogabout 0.32 m/s what beat frequency would you expect if 5.50-MHz ultrasound waves were directed along the flow and reflected from the red blood cellbo +hs7)o mu5 aygi r8ke6:x naxg+63h5gtp.qs? 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 t 41odxnuf+k5 mk71) oeisob4w oward 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 by the bat after that 54ubk+ x7)owino fdmsoe114k wave reflects off the moth?    kHz

  A bat emits a series of high frequency 6pt/yr+2czn zh,)g5t r w(naasound pulses as it approaches a moth. The pulses are approximately 70.0 ms apart, and each is about 3.0 ms long. How far away can the moth be detected by the bgw y),(+6nz pt/ thazr25 ncraat so that the echo from one chirp returns before the next chirp is emitted?    m

The “alpenhorn” (Fig. 1p cszp g08y6/c2–38) 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 insts c8/6 pgzc0yprument, the alpenhorn must be blown in such a way that only one of the overtones is resonating. The most popular alpenhorn is about 3.4 m long, and it is called the F sharp (or G flat) horn. What is the fundamental frequency of this horn, and which overtone is close to F sharp? (See Table 12–3.) Model as an open tube.

  Room acoustics for stereo listening can be compromised by rwx6hd .+2a)q koc x3lthe presence of standing waves, which can cause acoustic “dead spots” at the locations of the pressure nodes. Consider a living room 5.0 m long, 4.0 m wide, and 2.8 m high. Calculate the fundamental frequencies for theq32.rk6d+o c)x awxlh standing waves in this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

  A dramatic demonstration, callaq*2o:jk 6xf2bo hrh6-rbtd*ed “singing 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 rod can :2b2hqho-6r6f job* artxk *dbe 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 the human ear at a frequency oz dxd7*t2).ckvvjpxr owo )..f about 1000 Hzpddo x72)o..r w*kjxc)ztvv. 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;,m8i23/j dfqn *ruuswi m k2s observer on the ground hears the sonic boom 1.5 min after the plane passes directly overhead. What iud/ wsm3;j, s2r 8*inkqf mu2is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboatkg:a b/*0s fn7cl5pst2; e gff 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