What is the evidence that sound .to3u cg55u+a9kcu k2meya6q9hm6 w(1i nmfc travels as a wave?

What is the evidence that sound is a fok c3lzieldr/u d::p +5rm of energy?

Children sometimes play with a kb44y+r/2j- evco.7t8 qbgom a n9vdk homemade “telephone” by attaching a string to the bottoms of two papb7gvcd2489 o m qat4kkbe-vr o/yj+.ner 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 from air into water, dwk9mtm.u :6 hw vom/832k)v azims/m po you expect the frequency or wavelengtkvtwvkam2/wu8 z/s6m :93 ip.m mhm )oh to change?

What evidence can you give that the speed of sound in air doeswe6 k/umnk9r 14*auxr29 bdii not depend significantly m xa / k9iw4rb92n6ku*ureid1on frequency?

The voice of a person 2bfo 3j4o1ulc5afb0s9 ixmz -who has inhaled helium sounds very high-pitched. Why?

How will the air temperature iny; -t:giz8v4 knlm0st a room affect the pitch of organ pipes?

Explain how a tube might be used as a filter to reducetop :.gh1b,4bfufb x+ the amplitude of sounds in various .otpx4 b1 f:bubg,h+ffrequency ranges. (An example is a car muffler.)

Why are the frets on a guitar (Fig. 12–30)cmwu/ l2z.l;h spaced closer together as you move up the fingerboard tow.;m/2hz ulw clard the bridge?

A noisy truck approaches jk:6 lo6q;b;yvdq *r byou from behind a building. Initially you hear it but cannot see it. When it emerges and you do see it, its sound is suddenly “brigb 6ojv d:r6b qy;kql*;hter” — 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 bfxlze 7h sr8w9 +ei5ryh1w k(0eats can be said to be due to “interference in time.” Explain.r+h5 xwiyh(8 7fr0elsz19wk e

In Fig. 12–16, if th3cujuo2gx* 1j e frequency of the speakers were lowered, would the points D and C (where destructive and constructive interferenoj23g u x1c*ujce occur) move farther apart or closer together?

Traditional methods of protecting the hearing of people who work in 4kfnh;(sr0 qk 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,4nf;hqskk0( r a device is used which detects the noise, inverts it electronically, then feeds it to the headphones in addition to the ambient noise. How could adding more noise reduce the sound levels reaching the ears?

Consider the two waves shown in Fig. 12–31. Eac3g r jd bk vj*/o, cfhse6+9f8uzwcs+/h 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), are the two component frequencic3fcr6w ++v/ g9 ehbkj8d /s*oszujf,es farther apart? Explain.
(12-31)
(12-18)

Is there a Doppler shift if the source and observer move in the same directiore7k90 :ej6 x r.z(o cfr,ttxmn, with the same velocit7orf9 :z t ,rx kj(ee.0t6xrcmy? Explain.

If a wind is blowing, will this alter y;d sic1r5o; ov, u0taj-8ogtthe frequency of the sound heard by a persoo cgosa;jy- 5;8 d uirovt0,t1n at rest with respect to the source? Is the wavelength or velocity changed?

Figure 12–32 shows various w j v09jfskf3w14znb/akj5b: positions of a child in motion on a swing. A monitor is blowing a whistle in front of the child on the ground. At which position, A through E, will the child hear sfw9 j4fj :5w / vazjkb013knbthe highest frequency for the sound of the whistle? Explain your reasoning.

  A hiker determines the length d;5bewvm ux:9 of a lake by listening for the echo of her shout reflected by a clifv5xmb; u: d9ewf at the far end of the lake. She hears the echo 2.0 s after shouting. Estimate the length of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship just below the waterl t d,rf3.(xkb +c/ror o6r.tthine. 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? kooxc( .t6/ ,.rf rrh+r3tbdt 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 ato9aletcf+n.) ws,6w q 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 abovzjcvg3 h2)0whrsazg07 :eps8 e a school of tuna on a foggy day. Without warning, an engine backfire occzzh ge)ra72p :gwh008svj3 csurs 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 cliff. The splash it makes when stri).e+;ydadwg b n) 3hbpking the water below is heard 3.5 s later. )e g; d a)b+3wnyd.phbHow high is the cliff?    m

  A person, with his ear to the ground, sees a hul yj) jlaza7*9)sre 6jge stone strike the concrete pavement. A momenlsjaj9 j eyz7r6) )a*lt 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 ere( ukh:qg5 vgl o)-6j, 4;gh6buj m6q y+ebyknror made over one mile of distance by the “5-second rule” for estimating the distance from a lightning strike if the temperaturob6u; 5u46gb jg)+m,y jen:v yq heq-k 6l(ghke is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity of a 8kt m*bz4ogx( sound 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 of7y .xm8x4 uuxc a sound whose intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a syriv.l7 b) olae70lr9ound level of 95 dB when fired simultaneously at a certain place, what will be the sound le b 7v0or7i9rlllay).e vel if only one is exploded? [Hint: Add intensities, not dB’s.]    dB

  A person standing a certain distance from an a i bu/5cfbipql1k e* bkr;( :2f9ec7zkirplane with four equally noisy jet enginz /f29kicqb5:l cke1 7(*f;ku berbipes 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: Add intensities, not dB’s.]    dB

  A cassette player is said to have a signal-to-noise ratio of 58 dB, ). 0lo,in k.csodpk,dwhereas for a CD player it is 95 dB. What is the ratio of intensities of ts on.d.icp,, ok0)lk dhe signal and the background noise for each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of sox;n+h wc 6l/h kfom86t0zdjs 8und from a person speaking in normal conversation. Use Table 12–2. Assume the sound spreads roughofsnk 6l +/8;cxm8wzhdht0j6 ly 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 whose a2pr mp7d;6)d.- bndf cndue v4rea 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, weft -/wn2 km8g w4d4smhile the more modest amplifier B is rated at 40 W. (a) Estimate the sound leg/nf8d2 ekw 4 tsm4-mwvel in 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 regis5ci(kwce11ddg 6zuxxv.4+z x mem:u9 tered 130 dB when placed 2.8 m in front of a loudspeeccm1wixv. uzz:g (+ex d 94du1m65xkaker 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 difference in sound level of 2.0 dB. Wh 4vlq;*6ydmfl 1:jxudat is the ratio of the amplitudes of two sounds whose levels differ by this amount? [Hint: See Sectyj;1 : lu 4fmld6dvx*qion 11–9.]$\approx$   

  If the amplitude of a sound wave is winucz:s o6,0l(ajo2tripled, (a) by what factor will the intensity increase? Increase by a facocs,2 60ia jzl: uwon(tor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal displacement amplitudes, but one has twice the frm i8+p.xudg4qyy8wk : 5x,yjs 38zhsc equency of the other. What is the ymcy4yzxkd.j:qipx s5 ,h8sg8+8w3u ratio of their intensities?   

  What would be the sound level (in dB) of a sound wave in air that correspondstfb nte*8xqd: d/6 mf) to a displacement amplitude of vibrating air molecule xmtt:ef)b6qdnd 8f*/s of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level to seem p:.:zcuh a.l)ewxo+ajm8;i d as loud as a 100-Hz tone that has a 50-dB sound level? (S wueh;o:p8.m: j)al cdzxia.+ee Fig. 12–6.)    dB

What are the lowest and highest frequencies that an ear can det:s1o zo0 zxogwn)+n 9ject when the sound level is 30 dBjnw)os+ on ozx1 9g0z:? (See Fig. 12–6.)

  Your auditory system2), *mjhifhpw:n l kz( can accommodate a huge range of sound levels. What is the ratio of higim:(fh h l*wjk2)znp, hest 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 freqi6 9f4/sslp pauency of 440 Hz. The length of the vibrating portion is 32 cm, and it has a mass of 0.35 g. Under what tension must the s4/69p sa lspiftring be placed?    N

  An organ pipe is 112 cm lon-dtosf w rs*b8wll53; g. What are the fundamental and first three audible overtones if thet3b 5lslo*frw -8 s;wd 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 expect from blowing acrosa);z bo5uwl v z77g2gfs the top of an empty soda bottle that is 18 cm deep, if yoa )5go z7g;fuz2vb 7lwu 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 pf6 ;h,ho8cck pipe organ with open-tube pipes spanning the range of humk,h op;chf86 can hearing (20 Hz to 20 kHz), what 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 Hz as its third zmt/:r lpyi.) harmonic. What will be its fundamental frequency if it is fingered at a length of only 60% of its origi/ i.)ymr:z tplnal length?   Hz

  An unfingered guitar string is 0.73 m long and is tuned to play E above middlep1(;- w6xmlmh m1 znat C (330 Hzt-w m 1n( ;zmlxahm16p).
(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 thaga3-eq*um 0rkt emits middle C (262 Hz) when the k-q 0gaume3r*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 2 .9 rvt0 xstjus; k:ueun,(s6 yupvqg51-1 gxi0 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece of the flute in Example 12–10 should the holfz5qqlutcs9s ; b3 ,h0e be that must be uncovered to play D above,szh39q fcltb; u0q5s 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 pml:wk2(h,bdp +xklgp3 7vt0sipe can resonate at 264 Hz, 440 Hz, and 616 Hz, but not at any other fre3(p+, k2x whk 7 0gt:dlblvpmsquencies in between. (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 ends. It resonates at two sww:kiplu.254 h pnyv0z7r s: duccessive k5n7 z :vih0uwy.wdls:p4rp2harmonics 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 +(v pla5+d oot$^{\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-o l t3b+o ii6.;veysv4m-long organ pipe i6yoloestb3i4+ v v;. 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 ith km 0 e7yr +8 wj+vzk-wtun44-o,zjms open to the outside and is closed at the other end by the eardrum. o rkmv4,h+jwm0y jz w--t4te7zu8 +knEstimate 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 2.0 s when trying to adjust t,6f4okjcw/ ym wo strings, one of which is sounding 4/o,mcjfk6y4 w 40 Hz. How far off in frequency is the other string? ±    Hz

  What is the beat frequency if middle C () o93 ex1ye(ixvt*iny 262 Hz) and $C^＃$ (277 Hz) are played together?    Hz What if each is played two octaves lower (each frequency reduced by a factor of 4)? $\approx$    Hz

  A certain dog whistle operates at 23.5 kHz, while another (brand X) oper7f -u9ry) +rmg tu:iylates at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whine of frequency 50u)-y ultym9r:f g7ri+ 00 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 tunin )k6,vnopsm g,vn pj-.g fork and 9 beats/s when sounded with a 355-Hz tuning fork. W j vn-p,p, mn)v6.sgokhat is the vibrational frequency of the string? Explain your reasoning.    Hz

  Two violin strings are tuned to the same freqb(v9by k 3gf k:p*o.vsuency, 294 Hz. The 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 Ef(*3:gbvkb. kv 9yospq. 11–13.]    Hz

  How many beats will be hlj 2lmq2f(,q neard if two identical flutes each try to play middle C (262 Hz), but one is at 5.0°C and q(2nf m jl2l,qthe other at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks,)duap j+,6c uy A, B, and C. Fork B has a frequency of 441 Hz; when A and B are sounded together, a beat frequenap,)y6 u+ujcd cy 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 1.80qq)k4 s+l(i ni m apart. A person stands 3.00 m from one speaker and 3.5q iq+)ln4(si k0 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 eo f/3-;o olojt0tq:uHz, but a piano tuner hears three beats every 2.0 s when they are plaelqo ;0:ou j3t -ftoo/yed 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 man j-3hply y8 mw53aguzvm 2-ki*y beats per second will be heard? (Assu3u pz-l 3 5 iwyay-vg28jmkmh*me T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a h(ek () inutu2certain fire engine’s siren is 1550 Hz when at rest. What frequency do you detect if you move with a (iht(u)2n uk espeed 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(pjgbb)h x)j t,tuk4; fire engine whose siren emits at 1550 Hz )gx tjjbb,tp )k4u ;h(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 sjn: wf1s2xgf: q2tt.pzalp-,l+d ak 8 1sdrm;ource is moving toward you at 15 m/8.s a+d-rsftq1lap,2:l jk1m; n f:zg w2 txdps versus you moving toward it at 15 m/s Are the two frequencies exactly the same? Are they close? $f'_{source\,movine}$    Hz
$f'_{observe\,movine}$    Hz
(b) Repeat the calculation for 150 m/s and then again
$f'_{source\,movine}$    $ \times10^{ 3}$Hz
$f'_{observer\,movine}$    $ \times10^{ 3}$Hz
(c) for 300 m/s What can you conclude about the asymmetry of the Doppler formulas?$f'_{source\,movine}$    $ \times10^{ 3}$Hz
$f'_{observer\,movine}$    $ \times10^{ 3}$Hz

  Two automobiles are equipped with the same single frequency horn. When one isc;qhfo83n4ho/ jb :rz at rest and the other is movh4h8o/3zc ;on :fbjqr ing toward the first at 15 m/s the driver at rest hears a beat frequency of 5.5 Hz. What is the frequency the horns emit? Assume T = 20 $^{\circ} $C    Hz

  A bat at rest sends /6e0 u v: pzkkhioj4 ,c:oud*iout ultrasonic 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 frei doz/ujhu4 ,e*: ckpio06k :vquency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed of 5 m/s As it flies, the bat emits anwvh38efqkpjuork0 jz36 9.+ m ultrasonic sound wave with frequk3 8em96jvzqr pf+ 0o.wj kh3uency 30.0 kHz. What frequency does the bat hear in the reflected wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experiments, amrq4c h;o b9,q tuba was played on a moving flat train car at a frequency of 75 Hz, and a second identical tuba played the same tone while at rest in the railway station. What beat frequency was heard if the train car approa9rqcmq4;,bo hched the station at a speed of 10 m/s ?   Hz

  A Doppler flow meter uses ultrasound waves to measure blood-flow speeds. Suppos4mz0c 8 f0x/3o9x 9 opoibmjbjbaq52me 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 themb jocf9xzm50 48 oamq/oi0bp92b 3x j expected beat frequency if blood is flowing in large leg arteries at 2 cm/s directly away from the sound source?   Hz

  The Doppler effect using ultrasonic waves of frequenccv ;evv t(q* xv*1;z59ndnlbry $2.25 \times10^{ 6}$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 the wind vel(e4g r+. jjsxg2:i8ukxj pymg e e..b+21fkkdocity is 12 m/s from the north, what frequency will observers hea+jk4 +ei8:yjgrk.us .b d22gm( exgx. 1fjpekr who are located, at rest,
(a) due north,   Hz
(b) due south,   Hz
(c) due east,    Hz
(d) due west, of the whistle? What frequency is heard by a cyclist heading    Hz
(e) north    Hz
(f) west, toward the whistle at 15 m/s?   Hz
Assume T = 20 $^{\circ} $C

  How fast is an object moving on land if its sma*kzvgz9dlr /m jn,5+wu 9j9 peed 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 sgjjr+r23c uwv:y n,9k peed of sound is 310 m/s (a) What is the angle the shock wave makes with the direction of the aiu yr3+jw k:r nv2gj9c,rplane’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 atmosphereffb;8 ,i0 ltee0 gco-e of a planet where the speed of sound is onlfb0,8gi;o ce-0fl te ey 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 ocean. Determine the shock wave alhh2bn6 t2w x:-mf;icngle it produnl-m :ix2hw2b 6f hc;tces
(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 0fs5wj ; d3gg2fjvv0g $/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly overhead and see a , kt4n 5q5x+xyg3jk: +5jocmfj3q dxw 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 2.0 km.o 5jqktx5g, +qjdcmnfjx k x+5y433: w 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 sonigxynuox 4;ur/mul035t 2/ uund pulses 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, what 2/y;lutr0un4 5g3 u x oxu/nmiis the minimum time between pulses (in fresh water)?    s

  Approximately how many octaves are there stc p5fexso z-5:,j 8s+jitg2in the human audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display called a a 1 +dz9 c9rv.+donhrosewer pipe symphony. It consists of many plastic pipv r.da+1zonorh+c9d 9es of various lengths, which are open on both ends.
(a) If the pipes have lengths of 3.0 m, 2.5 m, 2.0 m, 1.5 m and 1.0 m, what frequencies will be heard by a visitor’s ear placed near the ends of the pipes?
$f_{3.0}$ =    Hz
$f_{2.5}$ =    Hz
$f_{2.0}$ =    Hz
$f_{1.5}$ $\approx$    Hz (Round to the nearest integer)
$f_{1.0}$ $\approx$    Hz (Round to the nearest integer)
(b) Why does this display work better on a noisy day than on a quiet day?

  A single mosquito 5.0 m from a person makes a sound qr53nhb+vmd:pz c c:1q; jhv;close to the threshold of human hearing (0 dB). Whaq5;djvrqn:zc : mch+pb;v 13ht will be the sound level of 1000 such mosquitoes?    dB

  What is the resultant soundt:xd9,c 1dpo(p+iddk level when an 82-dB sound and an 87-dB sound are heardd d1dp:k9cd ,oi(px+t simultaneously?    dB

  The sound level 12.0 m from a loudspctnf 98j tfh7h,iv x))eaker, placed in the open, is 105 dB. What is the acoustic power output (W) of the speaker, assuming it rad t9j,n)8ic)7hvtf xh fiates equally in all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 Hz. The powe8 kpc et5a3mu0)vgb 3+w9mtoor output drops by 10 dB at 15 kHz. What is the power output in watts at 15 k c3+) 9p5tt 3am8ouemok0 gbvwHz?    dB

  Workers around jet aircraft typically wear protective devices o-s.ngzntf q1 /ver 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 human ear has an effective radius of 2.0 cm. What would be the power intercsz /f.1-gtnqnepted by an unprotected ear at a distance of 30 m from a jet airplane engine?    W

  In audio and communication 5w msq+4azht:s 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 frequency g2*u ) a.gpvkgf(xuxy9:.iz f1uy ,no1$\frac{1}{2}$ 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 exwjns,wpp. e 1d72m+ between fixed points with a fundamental fmn7w,e2wp1s+j.e p xd requency of 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 fi2mnw/m nc*d d0qgjcbg8h;o * 3lled with water (Fig. 12–35). The water level is allowed to drop slowly. As it does so, the airw2g j gc ncmdmqb 8d;*/n*h30o in the tube above the water level is heard to resonate with the tuning fork when the distance from the tube opening to the water level is 0.125 m and again at 0.395 m. What is the frequency of the tuning fork?   Hz

  A 75-cm-long guitar string of mass 2.10 g is near a tube that is op7pzl ul96rlbw +5v s-qen 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 havp-sw9 q67z5lll+bu r rmonic in the tube?    $ \times10^{ 2}$ N

A highway overpass was observed to/tvfkag0sw936x-fj 2qlxymj5hawbs+: f ;5 u resonate as one full loop ($\frac{1}{2}\lambda$) when a small earthquake shook the ground vertically at 4.0 Hz. The highway department put a support at the center of the overpass, anchoring it to the ground as shown in Fig. 12–36. What resonant frequency would you now expect for the overpass? Earthquakes rarely do significant shaking above 5 or 6 Hz. Did the modifications do any good?

  A person hears a pure tone in the 500–1000-Hz x-z3q 9xp bgg5range coming from two sources. The sound is loudest at points equidistant from the two xbp3x-5qg g9 zsources. 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 th66c2y w gtl zd0d4(ylwe stationary train hears a 3.0-Hz beat frelw0czyydg d(t 64l6w2 quency when the other train approaches. What is the speed of the moving train?   m/s

  The frequency of a steam train whistle as it approaf21cwq xc0o ,jches you is 538 Hz. After it passes you, its frequency is measured as 486 Hz. How fast was the tra,of0cxcjqw 12in moving (assume constant velocity)?    m/s

  At a race track, you can estimate the speed of cars just byevlkn5p9s 1 e1m)p3ny 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 straigh5ys) 3enn19evl mpp1k taway. How fast is it going?    m/s

  Two open organ pipes,ag p .8gcg m wm9xj-/;z.jw*iezzb95m sounding together, produce a beat frequency of 11 Hz. The shortemgz.cwmgm ;.9 -aj*/pijb95z z8gxew r one is 2.40 m long. How long is the other?    m

Two loudspeakers are at opposite ends of a railroad car as it movh1- xi x6wfn9kes 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 s xx1i nw-6khf9peakers, at B, and (c) he hears the speakers after they have passed him, at C?

  If the velocity of blood flow in the z/lxe(w35vb z0m9idbaorta is normally about 0.32 m/s what beat frequenc/09wd zlbbv(m 3i5 ezxy would you expect if 5.50-MHz ultrasound waves were directed along the flow and reflected from the red blood cells? Assume that the waves travel with a speed of $1.54 \times10^{3 }$ m/s   $ \times10^{3 }$Hz

  A bat flies toward a moth at speed 6.5 m/)v zl3lr 8w4ops while the moth is flying toward the barl8l)vw4oz3 pt 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 wave reflects off the moth?    kHz

  A bat emits a series of )0, l utucpua;s -ht:d/i(fpu high frequency 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 the bat so that the echo from one chirp returns before the next chirp is emitted? - a/ ucdspuu,l)(tpt i:h f0;u   m

The “alpenhorn” (Fig. 12–38) was once used to send signals from one Alpine vilawo-b 2lf+u54u swuhgel;y ymh+ 2*a6lage to another. Since lower y4l;y +hmgu*a -lao5ws+2 u fe6h2buwfrequency 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.) Model as an open tube.

  Room acoustics for stereo listening can be compromc gkg0 fp66j,r o8mt7gised by the presence of standing waves, which can cause acoustic “dead spots” at the locations of the pressure nodes. Consider a lig0rkg pmgf7c86j t,6 oving room 5.0 m long, 4.0 m wide, and 2.8 m high. Calculate the fundamental frequencies for the standing waves in this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

  A dramatic demonstration, called “singing rods,” involves a long, slender aluminpm 5i2wms nj5vam/(0m um rod held in the hand near the ro0mjpwm 52(/vnm si am5d’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 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 i1ij t8qzbm, .a frequency of ab qm8t1,iibj. zout 1000 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 u5/v- sol6grr observer on the ground hears the sonic boom 1.5 min after the plane passes directly overhead. What is the plane’s altitug6solruv5/ -r de?    $ \times10^{4 }$ m

  The wake of a speedboy8))etwh-a 1 9gxjab bat 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