What is the evidence that soundt g whti;(bb l,/+ur 53skaof/xg)+ zn travels as a wave?

What is the evidence that c)s*3vlxx j2b sound is a form of energy?

Children sometimes play with a homemade “telephone” by attacmz (kv9mtf,t/ : le.sphing a string to the bottoms of two paper cups. When the string is stretched and a child sp/:pktme tzs .,v9mf(leaks into one cup, the sound can be heard at the other cup (Fig. 12–29). Explain clearly how the sound wave travels from one cup to the other.

When a sound wave passes from air into water, do you expect t9ui upgr06:g bhe frequency or wavelength u:ggiu9rb6 p0to change?

What evidence can you give that the speed of sound in air does not depend si3whp64ev; oh vgnificantly on fr6ph4 ho3ev wv;equency?

The voice of a person who has inhalv:d(envo.( v5pag b t5wn5c8eed helium sounds very high-pitched. Why?

How will the air temperature in a room affect the kck8 y-qnkk gn/12o :dmp fxs q*r,7f)pitch of organ pipes?

Explain how a tube might be used as atf9iyhk6k3l z,x - f5yhk:0ylt)3tox4c kh f, filter to reduce the amplitude of sounds in vari 5i9z)fyytk3t fyxo-flhk06 h,hc :lk t4xk,3ous frequency ranges. (An example is a car muffler.)

Why are the frets on a 8nh/2zu6 - x9xkzft chguitar (Fig. 12–30) spaced closer together as you move up the fingerboard toward the buz6/nck8zhx 2 fxh-t 9ridge?

A noisy truck approaches you from behind a building. Initially you hear it but tqc,ssh:g-8zi b7dm1sfz9. d cannot see it. When it emerges and yh sb :1d.f7z gm9,sciq-s8 zdtou 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 dhw3cr. .n 0obbeats can be said to be due to “interferehc0 bnw rod3..nce in time.” Explain.

In Fig. 12–16, if the frequency 3bqxa- fbjeu2c8 gc;,of the speakers were lowered, would the points D and C (where destructive and constructive ,q8 c;ja be2gb3f-u cxinterference occur) move farther apart or closer together?

Traditional methods of protec (ol .lxmvs((dting 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 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 addox(ll(.vms (dition to the ambient noise. How could adding more noise reduce the sound levels reaching the ears?

Consider the two waves mon 5*8iml,mwk+i: *(bpjptlqa+sl 5shown in Fig. 12–31. Each wave can be thought of as a superposition of two sound waves with slightly different frequet :( +mmqi a5oilplbk**sn,mpl8 w +j5ncies, as in Fig. 12–18. In which of the waves, (a) or (b), are the two component frequencies farther apart? Explain.
(12-31)
(12-18)

Is there a Doppler shift if the source fwvupv,n+8kx y(e-z7)kq 9efand observer move in the same direction, with thzvkw,pqkv7)-8 +fx(eu9 eyf ne same velocity? Explain.

If a wind is blowing, will this alter the frequency of the s od: ib)oh;mbw w*5+vzound heard by a person at rest with respect to the source? Is the wavelength or velocity changed?5o*dwb:imz v+w;hb o )

Figure 12–32 shows various positions of a chil8*o+ gumosodi2w3xw0 x,+q z td in motion on a swing. A monitor is blowing a whistle in w*3qwg s,8d 2++ooxiu mto 0zxfront of the child on the ground. At which position, A through E, will the child hear the highest frequency for the sound of the whistle? Explain your reasoning.

  A hiker determines the length of a lake by listening for the echo of her shoutk euz )f9q ;y0zi74bug reflected by a cliff at the far end of the lake. She hears the echo 2.0 s after shouting. Estimate the length o yui7);9qzfge 4zubk 0f the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship ju27nx0g7p p uasst below the waterline. He hears the echo of the sound reflected from the ocean floor directly below 2.5 s later. How deep is the ocean 7aps7n 20xgpuat 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 wav1d;7 hgphdol8w)9j*pw6wt or elengths in air at 20 $^{\circ} $ C for sounds in the maximum range of human hearing, 20 Hz to 20,000 Hz. $\lambda_{20Hz}$ =    m $\lambda_{20kHz}$ =    $ \times10^{-2 }$ m(b) What is the wavelength of a 10-MHz ultrasonic wave?    $ \times10^{ -5}$m

  An ocean fishing boat is drifting just above a school of tuna on a f(5)8 scq/((;q q13bykyhnq 9e ylbfvrj yxl*soggy day. Without warning, an engine backfire occurs on another boat 1.0 km away (Fig. 12–33). How much time elapses before thexr(;yl y nc1sj3q(kyfbq b/q*sqve()8 l y9h5 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 makejm2 60 mx d654bfa3 i smg* edjkuc-ps;;edn:us when striking the water below is heard 3.5 s later. H 2;5ce*;jn igemax0fj3p:u dssdd6u64 k-bm mow high is the cliff?    m

  A person, with his ear to the ground, z2u-j m7w 6q,1ypivgc sees a huge stone strike the concrete pavement. A moment later two s7u - zg2jc6yp1mi,w qvounds 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 by the “5-sem-qgey4+clv swva2,vf q,6e;cond rule” for estimating the distance from a lc-feve;wyv+ g2am 6 qvqs, ,l4ightning 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 lev qu.y + )oi/mgf5jh1i;q 9gcigel 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 levfux l r8z9r3t0el of a sound whose intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sousse1sm2: vgyn m 3ix:hhg*( 5knd level of 95 dB when fired simultaneously at a certain place, what will be the sound level if only one is explos s3hg1vhe::5*sy2 mxn (kig mded? [Hint: Add intensities, not dB’s.]    dB

  A person standing a certain distance from an airplane wi:5 3dfon8 xn,/h.ob bg+rnxfsth four equally noisy jet engines i,:xn n x8.5 fhs bn/+o3bdrgfos 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: Add intensities, not dB’s.]    dB

  A cassette player is said to have a signal- o fd;)9yqn:e:ds75gnmxjshx 1 px6u.to-noise ratio of 58 dB, whereas for a CD playen dg:xmsds1;o5e7u xhp6xfqj )9 :.ny r it is 95 dB. What is the ratio of intensities of the signal and the background noise for each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of sound from a person speaking in normal conversl8n91gqrtjg -ation. Use Table 12–2. Assume the sound spreads rougg -rgt189l njqhly uniformly over a sphere centered on the mouth. $\approx$    $ \times10^{ -6}$W(Round to the nearest integer)
(b) How many people would it take to produce a total sound output of 100 W of ordinary conversation? [Hint: Add intensities, not dB’s.]$\approx$    $ \times10^{7}$people

  A 50-dB sound wave strikes an eardrum whoseq/*.2 k7ndz;22zzyb iu b 8hnmrry9d t 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 moez.rikme(dgacg ,* :g91/vj. w 6t:p dyzxbl .re 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 loudspeaker 1.da .gdk:e m(z9gyb/*z ,epl jgx c .tri6wv: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 placed 2/; in*lllrq) d.8 m in front of a loudspeaker on thelrl* nl)iq; d/ 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 typicr) .fnyj9n v-jally detect a difference in sound level of 2.0 dB. What is the ratio of the vyn n.rf- j9)jamplitudes 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 fwck8nynwt2n6v-s3j2 w(;it t actor will the intensity increase? Increase s3y(v win 6n; t-jnwktt22c 8wby a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal displacement amplitudes, but one has twico20c.lbd 9gch e the frequency ooblhc9 d02.cg f the other. What is the ratio of their intensities?   

  What would be the sound level (in dB) of a sound wave vm26m msm m 6c4x:zg*kfj d mb3 nxm29v1f34omin air that corresponds to a displacement amplitude of vibrating air mol mmvmx3zcjm g 39v2mx:ob* sf6dk 1m 42n6mfm4ecules of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level to seem as loud asg e:(lw*5 rhjj a 100-Hz tone that has a 50-dB sound level?5(g:hjejr w l* (See Fig. 12–6.)    dB

What are the lowest and highest frequencies that an ear can detec1d q8 4v ,,zjramdaub9t when the sound level is1 84jvza uraq, mdb,9d 30 dB? (See Fig. 12–6.)

  Your auditory system can accommodate a hug3w)8h sfwi6h ae range of sound levels. What is the ratio of highesthh8if 6)wasw3 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 funw-e q*s gd8e*odamental frequency of 440 Hz. The length of the vibrating portion is 32 cm, and it has a mags*woe-d *qe8ss of 0.35 g. Under what tension must the string be placed?    N

  An organ pipe is 112 cm (sol+xs0n dmyzif m +110w)rd long. What are the fundamental and first three audible o0sn(z+drf+ osdxm)wl 1y1i 0mvertones 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 frequenk k,1( prgnxp5cy 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 tube?gk (npk1x5p,r    Hz (b) How would that change if it was one-third full of soda?   Hz

  If you were to build a pipe organ with 6znei(p8+ ;+ :q6m -ciux uq h+aruwyyopen-tube pipes spanning the range of human hearing (20 Hz to 20 kHz), what would be the8r awi-z6i uq:uc huy+x+ ;py6qmn(e+ range of the lengths of pipes required? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

  A tight guitar string has a frequency of 540 Hz as its third harmoni)c*feaslfhm 7w1 bx,*jloi ;1c. What will be its fundame,scf x*)*jlobilm;h1a7 wf1ental frequency if it is fingered at a length of only 60% of its original length?   Hz

  An unfingered guitar string is 0.73 m long and ism3 dn )lqh2a8baa1fy , tuned to play E above middle C (330 baq3af281) adln yh ,mHz).
(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 emit* h ji0k/rhht1s middle C (262 Hz) when the tempj0/*1 thrhih kerature 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 2aq1 c6q8zcn r40 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece of the flute i.h jbh:0an(c6sr+*pza1o qlin Example 12–10 should the hole be that must be u0jazs1c.qlhbp+ 6r :i(n*hoancovered 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, msk3sj,. rbv2 and 616 Hz, but not at any other frequencies in between. (a) Show why this is an 3 srj2,mbs v.kopen 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 ends. ik*grbg s5(i+nd8r *o It resonates at two successive harmonics of frequencies 275 Hz and 330 Hz. Whad*rgb58*n sk(oiig +rt 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 jh( ow. l.bl;r$^{\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 audiblrxib * 8a*d+vde range for a 2.14-m-long organ pi*i dd*rxba v8+pe at 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximately 2.5 cm long. It is open to td e * 1a:j*kj,p;c+-w tsjyczv*,xpfthe outside and is closed at the other end by the eardrum. Estimate the frequencies (in the audible range) of the standing waves in the epf**:+sc tj*,vxdtc- awjy1; pkzj,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 2.0 s when trying to adjust two strings, onex3yfk w bsu9xd5ddi58. (od5xu(isn ) of which is sounding 440 Hz. How far off in frequency is the other string uib nx.dw dd 5x(sk8 o5sd93f)ix5uy(? ±    Hz

  What is the beat frequency if middle C (262 Hz) and-:/w0c lcxj sla k34zq);.zkpga+vhj $C^＃$ (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 atky j :9n5inns.z)l/iz5r2lv7ljmgk7 t4j;vd 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, estima7gt 9v;inz)r.l jkk:mv 52l7jjs4 /l dnzyin5te the operating frequency of brand X.    kHz

  A guitar string producesdwl7:)r8re hp :hpr b( 4 beats/s when sounded with a 350-Hz tuning fork and 9 beats/s when sounded with a 355-Hz tuning fork. What is the vibrational frequency of the stri d):b:w8ph pr7l(hrer ng? Explain your reasoning.    Hz

  Two violin strings are tuned to the same frequency, 294 Hz. The tension in oy :()u:9scm8s (bxeo lczvl/pne string is then decreased by 2.0%. What wscl/8e:cyvx:u s9p ( ml)zb(oill be the beat frequency heard when the two strings are played together? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be heard if two identical flutes ea0os(qm ,ohv (ech try to play middle C (262 Hz), but one is hqo (,(se 0vmoat 5.0°C and the other at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks, A, B, and C. Fork B has a frequency of 441 Hz; w8qq xycg; 1pr,hen A and8,qgy xc r1;pq B are sounded together, a beat frequency of 3 Hz is heard. When B and C are sounded together, the beat frequency is 4 Hz. What are the possible frequencies of A and C? What beat frequencies are possible when A and C are sounded 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 stand ,4oo*pp )lnqi(ir bt9i5zz6zs 3.00 m from one speaker and 3.50*,ii6bl4nt)5p ozoq(z9 rp iz 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, bus63cx qcn9 .rbtvwp9 xn9:j gel 7ojs36 zj/)ut a piano tuner hears three beats every 2.0 s when they are played onc:tj l3nu/ .cjsp969q3sx v7r96jgb)ezxw together. (a) If one is vibrating at 132 Hz, what must be the frequency of the other ?   Hz    Hz
(b) By how much (in percent) must the tension be increased or decreased to bring them in tune?   % increase    %decrease

  A source emits sound of wavelengths 2.64 m and 2.76 m in air. How many bea7 ipit(o+ l;ba6u /ydets per 6o+/ upda;(y b il7teisecond will be heard? (Assume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a )dt *nwyqv 46slb5h)i; bmsq2certain fire engine’s siren is 1550 Hz when at rest. What frequency i2v nd*wl )bs 4y6)qtb;h smq5do you detect if you move with a speed of 30 m/s
(a) toward the fire engine,    Hz
(b) away from it?   Hz

  You are standing still. What frequency do you detect if a fire engine n kcutzwua ms+f. -*gizh8)06 whose siren emits at tu 6zn )zuf+amk8 *i -.w0hgcs1550 Hz moves at a speed of 32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift in frequency if a 2000-Hz source is moving towar;il/4sf:eh t 9egs)vn d you at 15 m/s versus you moving toward it at 15 m/s Are the two frel9:tevh e;i/4 sg sn)fquencies 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 equ35 n axnx-jt6zipped 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 H- tz53nj6xanxz. What is the frequency the horns emit? Assume T = 20 $^{\circ} $C    Hz

  A bat at rest sends out ultrasonic /m:/i wb nzsrdvb g,( :mfxc6/sound waves at 50.0 kHz and receives them returned from an object moving directly away from it at 25 m/s What is the received sound frequencbsr/(bdzm/w:i: xc/6 ,vngm f y?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall vz v4qr0j8r,t.;ws(rwg2fx l at a speed 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 reflqv,tr4 .2; zv r 0(xwsfwgj8rlected wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experiment/ sxh8(:i jlats, a tuba was played on a moving flat train car at a frequency of 75 Hz, and a second identical tuba playe :8/lsxht(a ijd 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 measure blood-flow speeds. Supposel6m gbs;l2g dfz k/)me:,/dif 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 gd ; k)eibmg2:dl,s/ 6lf/fmz 2 cm/s directly away from the sound source?   Hz

  The Doppler effect using ultrasonic waves of frequenab h- ys/o.y;bcy $2.25 \times10^{ 6}$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 H/ nps 8y(sojy m8)tbb7z. When the wind velocity is 12 m/s from the north, what frequency will observers hear who are located, at rest,p 88 7bm(tns)y/bjs oy
(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 ifdh2 5 z3n7csyk 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 speed of sound is 310 m/s (a) What 4ho.h80q eus dis the angle the shock wave makes with the direct u8he4h0d q.soion 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 iwb wt67m26j za planet where the speed of sound is7jmtb2 wiw66z only about 35 m/s
(a) What is the probe’s Mach number if its initial speed is 15000 km/h$\approx$    (Round to the nearest integer)
(b) What is the angle of the shock wave relative to the direction of motion?    $^{\circ} $

  A meteorite traveling 8500 m/s strikes the ocea4crtpxd(4x6r n. Determine the shock wave angle it proxpct4dr r64(x 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 cg3 ya3y,e fmqf/+fq0u453vp zl pi2g$/theta$ 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 grx6g qh h7q:7ddound flying faster than the speed of sound. By the ti7 q:xq6d7hh dgme 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 pulses dow2(.c0lq9 fv ho)( ;al e9fcpyvtqpbt :nward from the bottom of the boat, and then detects echoes. If the maximum depth for which it is designed to work is 200 m, what is the minimum time between pul)af:veqt(yot2p b.pcl; (9hq0 fc v9lses (in fresh water)?    s

  Approximately how many octaves a1 )e4,vs t yz+diq/x+ royq.pure there in the human audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display called a sewer pipe 6ya 6c)o1yrg4r ouyn 4:biu-p symphony. It consists of many plastic pipes of various lengthsruur4 oy4b 6ocn-yagyp6i ): 1, 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 close z afq.8vrvbktw u )9+4to the threshold of human hef. tqk) zbauw+v8 4r9varing (0 dB). What will be the sound level of 1000 such mosquitoes?    dB

  What is the resultant sound level when an 82-dB sound and an 87-dB sound a : xnqg*fj8ow/t-bz3seb +;:hrxilf 7re heard simultaneousl ljzgrn : /os3-t:efb 7wqfh8;b*x+xiy?    dB

  The sound level 12.0 m m 2f (ds2dr:pvuex,3nfrom a loudspeaker, placed in the open, is 105 dB. What is the acoustic power outpu ,smx pvd(f3n2e r:u2dt (W) of the speaker, assuming it radiates equally in all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 H:39on)l 0br pcuhbb q3z. The power output drops by 10 dB at 15 kHz. What is the power output in p3rnbb:l0 )b3 9ohcqu watts at 15 kHz?    dB

  Workers around jet aircraft typically wear h :80hgr esfx+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 txgf 0s8e:r +hhhe average human ear has an effective radius of 2.0 cm. What would be the power intercepted by an unprotected ear at a distance of 30 m from a jet airplane engine?    W

  In audio and communications systems, the ga s528z:n ;sltevuj7rbin, $\beta$ 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 q gvf0 i)eg)n9) sztvm4k;*cj tuned 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 fixn1o6bd /+ gm7-rpgoc73ax zi dz u1lp0ed points with a fundamental frequency of 4a c+op po b71r7gun iz0d3d1/6l mxzg-40 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 t/l(i x.,svtn uube filled with water (Fig. 12–35). The water level is allowed to drop slowly. As it does so, the air in the tube above the(n/ilx.st, uv water level is heard to resonate with the tuning fork when the distance from the tube opening to the water level is 0.125 m and again at 0.395 m. What is the frequency of the tuning fork?   Hz

  A 75-cm-long guitar strinnn+1fnt6s(mkro ,j4 ht54wbc g of mass 2.10 g is near a tube that is open at one end and a5w 6njhotkr mfbs4 4,1(c ntn+lso 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 tube?    $ \times10^{ 2}$ N

A highway overpass was observed to resonate as one full loopr*x,:yv9 rvkt bbe3c 4 ($\frac{1}{2}\lambda$) when a small earthquake shook the ground vertically at 4.0 Hz. The highway department put a support at the center of the overpass, anchoring it to the ground as shown in Fig. 12–36. What resonant frequency would you now expect for the overpass? Earthquakes rarely do significant shaking above 5 or 6 Hz. Did the modifications do any good?

  A person hears a pure tone in the 500–1000-Hz range coming from two so -wc8x9;jxn w:/ snuxw50 ejkcurces. The sound is loudest at poinj;wc:sxcu0 x9ke5/ wnxw8n j-ts equidistant from the two sources. To determine exactly what the frequency is, the person moves about and finds that the sound level is minimal at a point 0.34 m farther from one source than the other. What is the frequency of the sound?   Hz

  Two trains emit 424-Hz whistles. One train is stationary. The conductor on oc407+l u3 /tsqzq2g1jhqchjrv 4n5 sthe stationary train hears a 3.0-Hz beat frequency when the other train approaches. What is the speed of the moving trainc4+4lhqzs2u h j o7 5q n/vcsqt3j1g0r?   m/s

  The frequency of a steam train whistle as it approaches you is wa )wl 5m) tr)q;q8xga538 Hz. After it passes you, its frequency is measured as 486 Hz. How fast was the train moving (assume constant velwt qgam)aq5) l8r ;)xwocity)?    m/s

  At a race track, you c-/ 6ayctv 1qs6ttcq 5uan 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 a full octave (frequency haltqcsqta/y-6vt156c u ved) as it goes by on the straightaway. How fast is it going?    m/s

  Two open organ pipes, sounding together, prob19.r;koh dn tduce a beat frequency of 11 Hz. The shorter one is 2.dkrtoh;nb. 19 40 m long. How long is the other?    m

Two loudspeakers are at opposite ends of a railroad car as it moves past a st2*3.wtbnnkt 6 3kr zjyationary 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 hears the speakers after they have passed him, ak3zk.ntbr wy* 2 3jt6nt C?

  If the velocity of blood flow in the aorta is normally about 0.32 m/s whnwouoa pzge:rm 8uqp4l;7v ( x *k.y20at beat frequency would you expect if 5.50-MHz ultrasound waves were directed along the flo up*m2nup ;v(0y k l8ozo:qagw 7re4.xw 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 mots.a+hn4b d4i xh at speed 6.5 m/s while the moth is flying toward the bat at speed 5 m/s The bat emits a sound wave of 51.35 kHz4hn4.+ba s dix. 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 f 0lxcg;,jxjs)requency sound 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 thej,s0j) x;cxl g bat so that the echo from one chirp returns before the next chirp is emitted?    m

The “alpenhorn” (Fig. 12–38) +lzsfrhu 1l7ebzj7/1lndh.dg:zd0 2was once used to send signals from one Alpine village to another. Since lower frequency sounds are less susceptible to intensity loss, long horns were used to create deep sounds. When played as a musical instrument, the alpenhorn must be blown in such a way that only one of the overtones is resonating. The most popular alpenhorn is about 3.4 m long, and it is called the F sharp (or G flat) horn. What is the fundamental frequency of this horn, and which overtone is close to F sharp? (See Table 12–3.) Mode1 7 rhlljefhsz10:uz/7g l.b d zn2dd+l as an open tube.

  Room acoustics for stereo listening can be compromipw efv.mpuorm . v1)ef0e.7k; sed by the presence of standing waves, which can cause arw)m.f0vmkeuf1 ppv e7.;.eo coustic “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 demonstrat9dw)q-y 59svvks0mx ( npyty* ion, called “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 be made to “sing,” or emit a clear, loud, ringing soun* - smt(0k9x9)yws y5 pvnqvydd. 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 freqbog;)qmb*wcv -2zd6 euency of about 1000 Hz is ;e6 )bgc mzd*-oqw2v b$I_0$ = $1 \times10^{12 } W / m^2$ 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 hearks80 -ngtu ka/ormkks p(1q/og6 z8n9s the sonic boom 1.5 mio 0o(nan uzpkq1 sk/kg8r- mtg9 s8k6/n after the plane passes directly overhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboat is 1i6nzdg(m( ,uky og x:,5 $^{\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