What is the evidencea+o8q rh arpm+-c(dj4z:/h hb that sound travels as a wave?

What is the evidence that sound is a fo b 3gh3vxv4sp.,gn* 7pbfn z8arm of energy?

Children sometimes play with a homemade “telephone” by attaching a /cv* :lr 5oby1jv;ble string to the bo1 y j/lovblr*5cb ev:;ttoms of two paper cups. When the string 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 u4 *xrqe:id6 vfrom air into water, do you expect the frequency or wavelength to change*xrv6qiude:4 ?

What evidence can you give that the speed of sound in air does not depeb1)yktaad-j ary..x 8nd significantly on fr.bxajt-.d 8 1kaa)y ryequency?

The voice of a person who has inhaled rei(tknio36x5i 4+z;n il y8whelium sounds very high-pitched. Why?

How will the air temperature i q j(r)y(gtsj)r/) qvsn a room affect the pitch of organ pipes?

Explain how a tube might be us ,lxy- w2hxz kanhya2vpz:1(j+cc /(wed as a filter to reduce the amplitude of sounds in various frequency rangx: hk( ycpwa(vx1cahy zn+l,2wz2 j-/ es. (An example is a car muffler.)

Why are the frets on a guita))axmfb ssxnt32 2 xi+r (Fig. 12–30) spaced closer together as you move up the fingerboard toward thm3 )tsx n) 2x2abis+fxe bridge?

A noisy truck approaches you from behind a building. Initially you hear cn26n .xrh:d- bv dpo7it but c nxdov7phcbd.2- n:r6annot 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.]

Standing waves can be said to be due to “interference in space,” whereas bm/whqoxkxv z2f) 2,.tx+r . uieats can be saiz 2xhu2xm.vowf.x +,tr)ik/qd to be due to “interference in time.” Explain.

In Fig. 12–16, if the frequency of thjf4 ohmx(t1-r e speakers were lowered, would the points D and C (or 4t1(xmh -fjwhere destructive and constructive interference occur) move farther apart or closer together?

Traditional methods of protecting the hearing of people who work in a+ofv*nwn,v; 6 c phb;mreas 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 thevnmw , h+6nopfcv;b ;* ambient noise. How could adding more noise reduce the sound levels reaching the ears?

Consider the two waves shown in Fig. 12–31. Eamwevx6dpr (o j;+7f5dch wave can be thought of as a superposition of two sound waves with slightly different frequencies, as in Fivep7;+5(o6r dwf dj xmg. 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 shif*8 v4xkcd0es5fjc3ytt if the source and observer move in the same direction, with the same velocitsk 5yf dxv4cte0*38jc y? Explain.

If a wind is blowing, will this alter the frequency of the sound hkpilqn )tax5vl 0*zuabv fgo 86jv8u+ rv*)/,eard by a person at rest with resp*lokzv5f0rql)8u p* v),ajx a/gv68+ n itbuvect to the source? Is the wavelength or velocity changed?

Figure 12–32 shows various positions of a child i. kljwp+ x 6p:/,v qkwmvj.j-dn motion on a swing. A monitor is blowing a whistle in front of the child on the ground. At which position, A through E,j.pvwml :q/ 6,jd kv-x.pjw+k will the child hear the highest frequency for the sound of the whistle? Explain your reasoning.

  A hiker determines the length of a lake by listening for the echo of her5zo 9 7eii86u (fr.jsogg3ltt shout reflected by a cliff at the far end of the lake. She hears the echo 2.0 s after sfrs8t .6zeo5 jgi3(ti lgu7o9houting. Estimate the length of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship just belo roja ,2tjs+s/w the waterline. He hears the echo of the sound reflected from the ocean floor directly below 2.5 s later. How deep is the ocean at this point? Assume the speed of sound in seawater is 1560 m/s (Table /t2oa,j jssr+12–1) and does not vary significantly with depth.    $ \times10^{ 3}$m

  (a) Calculate the wavelengths inq)lig 2w ba czzh2okbeaw,6, ,go+ 6c1 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 11al cc,ot ys,of tuna on a foggy day. Without warning, an engine backfire occuro c,1t lycsa,1s on another boat 1.0 km away (Fig. 12–33). How much time elapses before the backfire is heard (a) by the fish,    s (b) by the fishermen?    s

  A stone is dropped from the top of a cliff6tmv fy;0 .ese. The splash it makes when striking the water m e0;st.fe6vy below is heard 3.5 s later. How high is the cliff?    m

  A person, with his ear to the ground, sees a hugf:an lt 1q:v(pe stone strike the concrete pavemen1 :l:v fn(qtpat. 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 12–1.$\approx$    $ \times10^{2 }$m

  Calculate the percent error made over one mile of distance b)*8mmd*uef704 ntzuzpo9h nod-d8i e y the “5-second rule” for estimating the distance from a lightning strike if the temperature is (a)7- efnhdm8*duni8o0pe )z9 mu *4dz to 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity of a soun6a2pjiada d.g(y,j xjp* ev08d at the pain level 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 soune70s5 *jh kwx( qe)0yzj /u7cflspui8d whose intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound level of l3-thcjs+wf6x4rdc;n, 5j kt 95 dB when fired simultaneously at a certain place, what will be the sound levelw+d53ljj ns;h4x ,f tkctr 6-c if only one is exploded? [Hint: Add intensities, not dB’s.]    dB

  A person standing a certain distance from an airplane with four equally noisyp z9e2mb8e2 m nnk31in jet engines is experiencing a sound level bordering on pain, 120 dB. What sound l9eek8nzn mm23np1 b2i evel would this person experience if the captain shut down all but one engine? [Hint: Add intensities, not dB’s.]    dB

  A cassette player is said to have a signal-to-na4 h0jof f9h,roise ratio of 58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensities of trjf4f90h oh a,he signal and the background noise for each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power outd r6,-6lq;, j.klvx:kgv pl ugput of sound from a person speaking in normal conversation. Use Tav:,.6lkg l; dlu,g-rxk6pqj v ble 12–2. Assume the sound spreads roughly uniformly over a sphere centered on the mouth. $\approx$    $ \times10^{ -6}$W(Round to the nearest integer)
(b) How many people would it take to produce a total sound output of 100 W of ordinary conversation? [Hint: Add intensities, not dB’s.]$\approx$    $ \times10^{7}$people

  A 50-dB sound wave strikes antsxl1 g ot jyzu0gb1*8q,p 6:g,0 hrww 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 ampli5eq: qodoz1r2px+; x)tkps q /fier B is rated at 40 W. (a) Estimate the sound level inek /q+:x5zopds ;xq 1t pr2)oq decibels you would expect at a point 3.5 m from a loudspeaker connected in turn to each amp.$I_{250}$ =    dB $I_{40}$ =    dB (b) Will the expensive amp sound twice as loud as the cheaper one?

  At a rock concert, a dB meter registered 130 dB when rgje:qb3g x:ny g2 (7s1n v1luplaced 2.8 m in front of a louduy2 jnggv:b1xe137s :ng (qlr speaker on the stage.
(a) What was the power output of the speaker, assuming uniform spherical spreading of the sound and neglecting absorption in the air?$\approx$    $ \times10^{2 }$W(“Round to one decimal place)
(b) How far away would the sound level be a somewhat reasonable 90 dB?   $ \times10^{2}$m

  Human beings can typically detect a dify m:x:g6*m io8faml:fference in sound level of 2.0 dB. What is the ratio of myf::ox 8 *ifa l6mm:gthe amplitudes of two sounds whose levels 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 intensji3 yc 87v 6vp(ton8.iy,zav6 -syjhxity inz s,8ihij ovc.y3 8tvjvya766xy(-npcrease? Increase 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 twice th+ eaesx*9lmxyd 9:.sp tq21bse frequency of the other. What is the ratio of their intensities?9d :.xmsxs 9pt+ qes*1be yla2   

  What would be the sound level (in dB) of a sound wave in air that cor5d) rfrp3xak .responds to a displacement amplitude of vibrating air molecules ofakd. x5rp3) rf 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have. uy .id1ra9 4:sqmblf9yd.o/yoh+t b what sound level to seem as loud as a 100-Hz tone that has a 50-dB sound level? (See Fig. 1249oai9qm +fr.b /lhdbd1 .oy sy u.:yt–6.)    dB

What are the lowest and highest frequencies tt6o .ww*)a1bcfd 5-vyqgt*ol hat an ear can detect when the sound level is 30 dB? (*. 1fw ytb-tv*qa cog5olw)6dSee Fig. 12–6.)

  Your auditory system can accommhc s.4( yx7hbp8e-x;ec + wawpodate a huge range of sound levels. What is the ratio of highest-yc8p;p wxes a wbhx.h ec4(7+ 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. The 9d x7myajuc9-qbl5w )vca+ (e length of the vibrating portion is 32 cm, and it has aqalcv+ wa(xm7j 9-y5dc eu)9 b mass of 0.35 g. Under what tension must the string be placed?    N

  An organ pipe is 112 cm long. What are the fundamental and first three auz k:jz (/ut:e,qmgz5 pdible overtom(tqjkpz::e,u/g zz5nes if the pipe is
(a) closed at one end, $f_{1}$ =    Hz $f_{3}$ =    Hz $f_{5}$ =    Hz $f_{7}$ =    Hz
(b) open at both ends?$f_{1}$ =    Hz $f_{2}$ =    Hz $f_{3}$ =    Hz $f_{4}$ =    Hz

  (a) What resonant frequency would you eoadafa( ( /8s7wdd8cexpect from blowing across the top of an empty soda bottle that is 18 cm deep, ef8 sddaw7( aoca/8d(if you assumed it was a closed tube?    Hz (b) How would that change if it was one-third full of soda?   Hz

  If you were to build a pipe organ wifl(9mi gyp: . pw5ad3wth open-tube pipes spanning the range of human hearing (20 Hz to 20 kHz), what would be the range of the lengths of pipes requl.wad(mpfy9p 3:wg i5ired? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

  A tight guitar string has a frequency of 540 Hz as ikfh .-az *kg5bts third harmonic. What will be its fundamental frequency if it is finf5aghzk b- k.*gered at a length of only 60% of its original length?   Hz

  An unfingered guitar string is 0.73 m long and is tun6tx 9le31vhx7y3r h m/ma-xb,xi c 8vsed to play E above middle C (h1 a-xb 3h mrv9cs/y6 v8xmtx, e3xil7330 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 emits )ab r:wg o7ko:middle C (262 Hz) when kgw oba:o 7r):the 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 at e3 xe3 5af5uu6s ns6eu20 $^{\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 12–10cf*j qi)b8u r6 should the hole be that must be uncovered to play D above middle C q6frib*uj8) cat 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, bg1:+usx enjjno/*ew5 ut not at any other frequencies in bn x*uj51n g e+w:se/ojetween. (a) Show why this is an open or a closed pipe. ----待选择----closedopen  (b) What is the fundamental frequency of this pipe?   Hz

  A uniform narrow tube 1.80 m long is open at both 3xnvm+my3e;c3c pmo5 ends. It resonates at two successive harmonics of frequencice5m+v;yc3n o p3mmx 3es 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 tw8,q;p,ug 5gr )e6jyjj 9oit$^{\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 preseq ; /(2anq 6v q93o8enj9vrpdgywzgn9nt within the audible range for a 2.14-m-long organ /93yv6;gqpdqj9( ogzna2n qw8nr9vepipe at 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximately 2.5wuyi2 70d beq- 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 information 0 7euib qyw-2din 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 6n9so1u i,li uto2wsj;2(/ pbqbcl4z two strings, one of which is sounding 440 Hz. How far off in frequency b,2l u;is9csnz b4p(j/ lo 1o2wtq6iuis the other string? ±    Hz

  What is the beat frequenc8dnn0 ch(nytps 3q z1e8y1hj ;y if middle C (262 Hz) and $C^＃$ (277 Hz) are played together?    Hz What if each is played two octaves lower (each frequency reduced by a factor of 4)? $\approx$    Hz

  A certain dog whistle opei wy;*vj5ec2n 4up:qarates at 23.5 kHz, while another (brand X) operates at an 4 ;wpv2:*n yc i5equajunknown 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 frequency of brand X.    kHz

  A guitar string produces 4 beats/s when sounded with a 350-Hz tun bo7ry1b p(:4t6 m*ktaogsio0ing fork and 9 beb o6yb0 p74 a:mr(kottigo 1s*ats/s when sounded 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, 294 Hz. 7/,1s dxtmeun-c) hocThe tension in one string is then decreased by 2.0%. What will be the beat frequency heard when the two strings are played together? [Hint: Recall Eq. 1 - )tm,/1ccnuxs 7deoh1–13.]    Hz

  How many beats will be heard if two identical flute-jeimh/qzg/83 .qjf ps each try to play middle C (262 Hz), but one is at 5.0°C and-qp3hi .ej8z g jq/mf/ the other at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks, A, B, and C. Fork B has a frequenamp1s 4,urxta/cn :z:cy of 441 Hz; when A and B are sounded together, a beat frequency of 3 Hz is heard. When B and C are sounded 1c a: un/:s,zatrxp4m together, the beat frequency is 4 Hz. What are the possible frequencies of A and C? What beat frequencies are possible when A and C are sounded together?$f_A$ =    Hz or    Hz
$f_C$ =    Hz or    Hz
|$f_A$-$f_C$|    Hz or    Hz

  Two loudspeakers are 1.80 m apart. A person stands 3.00 m from one s;jnb9qmn*y ;/pv0hs h peaker and 3.j/q9vnps 0*hnm;bhy ;50 m from the 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, but a piano tuner,yel.aaa. ih()stct0 hears three beats every 2.0 s when they are .ea hl,isacty).0at( played together. (a) If one is vibrating at 132 Hz, what must be the frequency of the other ?   Hz    Hz
(b) By how much (in percent) must the tension be increased or decreased to bring them in tune?   % increase    %decrease

  A source emits sound of wavelengths 2.64 qfc 97wnnt8*bgu8i-ekh88 ar m and 2.76 m in air. How many beats per second will be hf h*a8ie87ubwkgn-qnc88 r9t eard? (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 if/le3u 8cw8j tu /*duat rest. What freque8etu /8iu dju3*lfcw/ncy 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 (6syi ;fm slt ayu1h4gqqzk*.(si0j5fire engine whose siren emits at 1550 Hz moves at;k *a 6qyshf(g40ji 1.s (zimltsq yu5 a speed of 32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift in frequency if es, (nqhj/e3sa 2000-Hz source is moving toward you at 15 m/s versus you moving toward it at 15 m/s Are the two fr3 ensj/ q(ehs,equencies 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 equippe 2bs8lezg9,cfgl bm fgm(y -1,d 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 freqzgfly,-28emf(g9 m g1b sb lc,uency the horns emit? Assume T = 20 $^{\circ} $C    Hz

  A bat at rest sends out ultrasonic sound waves at 50.0 kHz and receives he7ke v;3z3k+i q9huvsey- 5qthem returned from an object moving directly away from it at 25 m/s What is 3q;yvi - z37hevq9hu+ e5ke ksthe received sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed of 5 m/s As it flies, the bat emiauc0 k8h6:vv:2z ol.e rbltq/ts an ultrasonic sound wave with frequency 30.0 kHz. What frequency do:ol6. v 2 qb0cv t8zea:hl/urkes the bat hear in the reflected wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experiments,+vav3i / vh7lzy28ah v 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 th7vzv a +2vh8h3/avilye train car approached the station at a speed of 10 m/s ?   Hz

  A Doppler flow meter uses u qm m)jg1m(3on0/mnn cltrasound waves to measure blood-flow speeds. Suppose the devicem(gn13momj0)/m n cqn 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.tve9hx2pm nobm 4 3r0 ultrasonic waves of frequency $2.25 \times10^{ 6}$Hz is used to monitor the heartbeat of a fetus. A (maximum) beat frequency of 500 Hz is observed. Assuming that the speed of sound in tissue is $1.54 \times10^{3 }$ m/s calculate the maximum velocity of the surface of the beating heart.    m/s

  A factory whistle emits sound of frequency 570 Hz. When thvrb t1(n r q)nyd(k--ye wind velocity is 12 m/s from the north, what frequency will observers hear wh(-nr)yyt(v r1 bkd-n qo 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 ljwoq:8syy 52 yand 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 speeldwbk: 0+yzk4v-vg18,vpks r d of sound is 310 m/s (a) What is the angle the sh0 1gr,+ skv4bk vlkpd-:wzyv8ock 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 the sy1 odzzo3 ;e4xpeed of sound is only a yo4xz e1;3zodbout 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 g*1f(7 o kn y9zs80jx7,cdr ib iak;pmm/s strikes the ocean. Determine the shock wave angle it pro(s*kbci r,n1k9 da0y8jg7op7z; i fxm duces
(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 j izo t7 r289gqfdqyj4b b3.w5$/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly overhead and see t0 btz x46j v6nn6nrmt9 h:eg0a plane exactly 1.5 km above the ground flying faster than the speed of sound. By the time you hear the sonic boom, the plane has traveled a horizontal distance of 2.0m:hnv6n0tzn6 g t09er 4btjx6 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 pulses downward frojfs+; i nyp1 bfg et,:gdh.+(pm the bottom of the boat, and then detects echoes. If the maximum depth for b 1ny:(p+deg+fhgp.jt;fis,which it is designed to work is 200 m, what is the minimum time between pulses (in fresh water)?    s

  Approximately how many octavko:bu s upcw+x0y3wy e eiu8 r1:bf++(es are there in the human audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum hasi12sw55gb ary a display called a sewer pipe symphony. It consists of many plastic pipes of varrg5 i25wybas1ious 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 person makes a sound c 2,9-tk0b sb;be3cyr b0wmv aa b9ckr2s2bk b5lose to the threshold of human hearing (0 dB). Whactbc brak2bb, 25ymsbk3bbv9 ;wks e -29 0r0at will be the sound level of 1000 such mosquitoes?    dB

  What is the resultant sound level when an ggdil9-uy/nec76cd)e t(uwsr69 hf , 82-dB sound and an 87-dB sound are heard simrg (cusye79d66 )h/9-i wd cf,ungtle ultaneously?    dB

  The sound level 12.0 m from a loudspeaker, pla.enzh ,o35auqez :n) 4)kksn )u*nuyrced in the open, is 105 dB. What is thqy) k)n54 n)zn,.*uzkr:e aue 3snouhe acoustic 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 outpj99pbf qc 8xp)ut drops by 10 dB at 15 kHz. What is the )p9x8pj qb9fcpower output in watts at 15 kHz?    dB

  Workers around jet aircraft typicii tj aygb5; 1 :gq98c7xheh6gally wear protective devices over their ears. Assume that the sound level of a jet airplane engine, at a distance of 30 m, is 140 dB, and that the average huy :9aeg7q ;ih1xg gh6ic5t8j bman 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 5m8rxhr1xavp8+k9g ky*3to) gjn 9bwns 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 tuned to a fre34 yo-s502a0iwspgoyu.,hrge 6xtzhgkm( h ( quency 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 bet+: s)wzrts1v vween fixed points with a fundamental frequency of 1s) zvsrv+:wt 440 Hz and a mass per unit length of $6.1 \times10^{-4 }$ kg/m
(a) What are the wave speed and tension in the string?    $ \times10^{2 }$ m/s    N
(b) What is the length of the tube of a simple wind instrument (say, an organ pipe) closed at one end whose fundamental is also 440 Hz if the speed of sound is in air?    m
(c) What is the frequency of the first overtone of each instrument?   Hz    Hz

  A tuning fork is set into vibration above a vertical open tube filled with u722nrpr2/ax m0 vkv swater (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 again at 0.395 m. What is the frequency of the tuning fork0p u r ms7vxkr2/a2v2n?   Hz

  A 75-cm-long guitar string of mass 2.10 g is near a tube tha(r(w)u3gavbe )+qe.* tfp rgxs b .iauu; a4y4t 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 third harmonic in the tubepuub;w3 avf( a(s* gxy +rrt4qu4.i)eg. )eba?    $ \times10^{ 2}$ N

A highway overpass was obserkl0 yw98js ja qt:2ye*ved 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 ddf y eg3w /o k(a2+3c4zjt4thtone in the 500–1000-Hz range coming from two sources. The sound is loudest at points equidistant from the two sources. To determine exactly what the frequency is, the perso+oth3z/k4a dj fdw42t3ecg( yn moves about and finds that the sound level is minimal at a point 0.34 m farther from one source than the other. What is the frequency of the sound?   Hz

  Two trains emit 424-Hz whistles. 5rbkoli 9 4;ahOne train is stationary. The conductor on the stationary train heaba ;5l9hro4ki rs a 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 you is 538 Hz. After it 24tvop l b09tcc nj+ ob5 5x:jgwm ar:3omb6b7passes you, its frequency is measured as 486 Hz. How fast was the train moving (assume constant veloc+7c :cj5bwp n xb b30oog52vmt9 6b4:rljatomity)?    m/s

  At a race track, you cq rkf. od b;:.snu7/zkan estimate the speed of 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 qk r.n;bzfdu7k:/. osa full octave (frequency halved) as it goes by on the straightaway. How fast is it going?    m/s

  Two open organ pipes, sopclc ) hy(p5 kqjk; ye6zo/g.-unding together, produce a beat frequency of 11 Hz. The shorter one is 2.40 m long. How e.cpo;q-z5c kjp yy kl)/h6g(long is the other?    m

Two loudspeakers are at opposite ends of a railroad car as it moves past a stati(h .v u(aj5, .fxbvzhlonary observer at 10 m/s as shown in Fig. 12–37. If the speakers h(.ua5j .x ,lhhvb(zvfave 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 hears the speakers after they have passed him, at C?

  If the velocity of blood flow in the aorta is normally about 0.32po 1i.j6 5pp;oglzzv 08fcq*o m/s what beat frequency would you expect if 5.50-MHz ultrasound waves were directed along the flow and reflected pczq g;60i5 pozl1ov ojf* 8p.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 6.5h4j5)j 1mivih m/s while the moth is flying toward the bat at speed 5 m/s The bat emits a sound wave of 51.35 kHz. What is the frequency of the wave detected by the bat after that wav)hv 4hi51m jjie reflects off the moth?    kHz

  A bat emits a series of high frequency sound :0lom v 7ftm:-3r lu3a bu5duhpulses 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 detec3 mru-fohl:d530a: v7l ubtumted by the bat so that the echo from one chirp returns before the next chirp is emitted?    m

The “alpenhorn” (Fig. 12–38) j8h;f yya9f* 1yei14lv t8atowas 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 f8; otylahi t8jy114 ev9ay*fa 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 comprv lp,9b*bc)h3 z/+rjl j1eegcomised by the presence of standing waves, which can cause acoustic “dead spots” at the locations of the pressure nodes. Consider a living roo3* h ,b ej19lj)e/+zrcbcvpglm 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,” ids+e mtn77y (g4+hy e wjmg*x:nvolves a long, slender aluminum rod held in the hand near the rod’s midpoint. Thmed g(jgemt +wy+nx4:s7y 7 *he rod is stroked with the other hand. With a little practice, the rod can be made to “sing,” or emit a clear, loud, ringing sound. For a 90-cm-long rod,
(a) what is the fundamental frequency of the sound?    $ \times10^{ 3}$ Hz
(b) What is its wavelength in the rod,    m
(c) what is the traveling wavelength in air at 20 $^{\circ} $ C?    m

  The intensity at the threshod69mmslitg:x 2 ,gm p/ld of hearing for the human ear at a frequency of about 100gmt:9m d6lx m/2 ,spig0 Hz is $I_0$ = $1 \times10^{12 } W / m^2$ for which $\beta$ the sound level, is 0 dB. The threshold of pain at the same frequency is about 120 dB, or $I$ = $1 W / m^2$ corresponding to an increase of intensity by a factor of $10^{12}$ By what factor does the displacement amplitude, A, vary? 10$^{a}$ a =   

  A plane is traveling at Mach 2.0. An observer on the ground hears 3 0i,7yzqd2k2br xvm sthe sonic boom 1.5 min after the plane passes directly ove2 miqsxrz3yvbk20,7drhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboatq-tb mzmkz ovs 7**-8zbxw x(0 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