What is the evidence that sound travelscz)xh ofzy7 /u46 x8qv as a wave?

What is the evidence that sound is a form of e(5,mi jvc( z :axdwi(fnergy?

Children sometimes play with a homemade “telephone” by attaching a string ft2i ry:pfu0fna, .z*e. xk d:to the bottoms of two paper cups. When the string is stretched and a child speaks into one cup, the sound can be heard at the other .:f.pkyt 2 u*0z,a :rfeixdfncup (Fig. 12–29). Explain clearly how the sound wave travels from one cup to the other.

When a sound wave passes from apwf0y 9o0 tgp+ir into water, do you expect the frequency or wavelength to 0pyg tp w+0fo9change?

What evidence can you give that the speed of sound in air does6frqzrn z hlx4k:9 v3rv98 0oa not depend significantvh99vzr oqrfza08 4l3 :x kn6rly on frequency?

The voice of a person who has inhaled helium sounds very roubi1dv0ti i3i7w* .eib85a high-pitched. Why?

How will the air temperature in a room affect the pitch of org/m -/2m zuvnnuan pipes?

Explain how a tube might be8xfni fqs;q55 l6sla8we 7-u p used as a filter to reduce the amplitude of sounds in various frequency ranges. (An exampl ua 55fes q8nlx6w7pl-qs8if;e is a car muffler.)

Why are the frets on a guitar (Fig. 12–30) spaced closerk*+ v phnmaoox,)a n7cj 5(ua2 together as you move up the fingerboard touo c k*n7ha2o+m()aa5j , pxnvward the bridge?

A noisy truck approaches you from behind a building. Initially you wmw 355rsdoae)eb l2.hear it but cannot see it. When it emerges and you do see it, its sound is suddenly “brighter” — you hear more of the high-frequency nois)b3eew2 rd55ol ws .ame. Explain. [Hint: See Section 11–15 on diffraction.]

Standing waves can be said tf,+ h+srvove2 o be due to “interference in space,” whereas beats can be said to be due to “interference in time.”2ef vr+svo+, h Explain.

In Fig. 12–16, if the frequs v io26 wz9kd6ywki(1ency of the speakers were lowered, would the points D an kv 61y9i(oww6kdz i2sd C (where destructive and constructive interference occur) move farther apart or closer together?

Traditional methods of protecting the hearing of people who worky9 imiafc6- 2n 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 mca-i26n fyi9that do not block the ambient noise. Instead, a device is used which detects the noise, inverts it electronically, then feeds it to the headphones in addition to the ambient noise. How could adding more noise reduce the sound levels reaching the ears?

Consider the two waves shown in Fig. 12–31. Evpdl (5l l9wfax,30 eoach 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 frequen3 lvf9lpelao,5xd (0wcies farther apart? Explain.
(12-31)
(12-18)

Is there a Doppler shift if the source and observer move in the same d 6kw0(x kiri 5 i1giqgm2nauojk (66d.irection, with the same veloci ki(w 6 i5aiqok.guxrg6k0i d1(mnj62ty? Explain.

If a wind is blowing, will this alter the freqjl9s3 4ut6dy6g)csr/ cf t*ymuency of the sound heard by a person at rest with respect to the source? Is the wavelength or veloc 66/4fj*gc3r tlmydy u ss9tc)ity changed?

Figure 12–32 shows various positions of a child in motion on a s5pe f.h2hw ps,qeod2 4wing. A monitor is blowing a whistle in front of the child on the ground. At which position, A through E, will the child hear the highest frequencyh4swde2eh,fqop 2 .5p for the sound of the whistle? Explain your reasoning.

  A hiker determines the length of a lake by listening for the echo of her shout rsu9nd gg(1ls1 *a3sv aeflected by a cliff at the far end of the lake. She hears the echo 2.0 s after shouting. Estimates ual9131*dn (vs ggas the length of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship just below aw;3f6t75 s hh pfv,npthe waterline. He hears the echo of w,a5fn6ft;h3p sh7pv 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 12–1) and does not vary significantly with depth.    $ \times10^{ 3}$m

  (a) Calculate the wavelengths 2 v7 5-r84 jcv yvlequal/ie qfq6n-)rin 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 tunwy7(+au*laqd 6lvn h(w a u3/ba on a foggy day. Without warning, an engine backfire occurs d(+lqb7*uhav a6l3 a/wwyun(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 +kubg*7nw +8f fvz (yjsplash it makes when striking the water below is heard 3.5 s later. How high is the cliff?kv +jb (*8yg+n f7zwuf    m

  A person, with his ear to the ground, sees a huge stone strike )y k,,3rsyo djwv-71rm)svoxthe concrete pavement. A moment later two v oyj )1sk,r3w sxvyd7-),orm 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 distanc- rd5za u+rl2ae by the “5-second rule” for estdrlra a5u+2 z-imating the distance from a lightning strike if the temperature is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity of a sound og;ds79u hog6at 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 soun zq+zqu/s l*v/k;h (k*.bn)hkdnjq/q d whose intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound level of 95 dB when fired simultanr. *q:x v3revleously at a certain place, whaqx.re*:l 3rvvt will be the sound level if only one is exploded? [Hint: Add intensities, not dB’s.]    dB

  A person standing a certain distance from b70zzt3 vcp0pan airplane with four equally noisy jet engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person experience if the captain shut down all but one engine? [Hint: Add intenszpczv300p7b tities, not dB’s.]    dB

  A cassette player is said to have a signal-to-noise ratio oflx. .qtu aght+0s52r f 58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensities of the signal and.u+ lsqfx 20 gh.ttr5a the background noise for each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the pow vni qu(mx-lib8*5 k8ger output of sound from a person speaking in normal conversation. Use Table 12–2. Assume the sound spreads roughl5 bn -kmu( ilqv8*8igxy 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 are b t87pgmx ir,j,m:w.la 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/g.ezm a.o;vx:9av -s3tvvgi at 250 W, while the more modest amplifier B is rated at 40 W. (a) Estimate the soum9-vz3:xsog/.via.gva t;v end level 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 mete)n9 4 dorf6hwx37 dqzyr registered 130 dB when placed 2.8 m in front of a loudspeaker on the s9q)63r fddowx7 yhnz4tage.
(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 soundjk549qmxkv1 :o k3 e:u7hju ev level of 2.0 dB. What is the ratio of the amplitudes of two soundq1 :4kuv3xmove 97 5 k:ujkjhes whose levels differ by this amount? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound wave is tripled, (a) by what f)ju; bcia 2ij)actor will the intensity increase? Increas ujb2))a;ji cie by a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have kd,uhf ti,1e1 equal displacement amplitudes, but one has twice the frequency of the othf1ed u1t ,,kiher. What is the ratio of their intensities?   

  What would be the sound level (in dB) of a sound wave in air that correspbg ,udoqg1ffu: ;uh77onds to a displacement amplitude of vibrating air molecules of 0.13 mm g b7h:1dguf 7,u qo;fuat 300 Hz?    dB

  A 6000-Hz tone must have what smq;u(rvls b51 ound level to seem as loud as a 100-Hz tone that has a 50-dB sound level? (Seu( vbrmq;1l5se Fig. 12–6.)    dB

What are the lowest and highest frequencies that ae8;bojy fvk108zj6nn n ear can detect when the sound level is bnv1nk zfo 6e808jjy; 30 dB? (See Fig. 12–6.)

  Your auditory system can accommodate a hugwlk4*fe dk 7j m5*ocx5y 2j(bpe range of sound levels. What is the ratio of highest to lowest intensity at *bdj m5 y5k4*w2 7epojl(kxcf
(a) 100 Hz,$ \times10^{ a }$ a =   
(b) 5000 Hz? $ \times10^{ a }$ a =   
(See Fig. 12–6.)

  The A string on a violin has a fun(n )j+fr lq(dzdamental frequency of 440 Hz. The length of the vibrating portiol+ drf(jq) nz(n is 32 cm, and it has a mass of 0.35 g. Under what tension must the string be placed?    N

  An organ pipe is 112 cm long. e;59ij )zewugy hn*u3What are the fundamental and first three audible ohwzyei9u j)5*3 nge;uvertones 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 expect fromv:5 jcf)a9(dmq bbi vlgrz1c;hqout4( : d-;m blowing across the top of an empty soda bottle that is 18 cm deep, if you assumed i md:hqq v1f(4mo cia d9t;ubb: ;v5g-zc(r)ljt 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 with open-9-jp3 zdw t7cqrtzf)- tube pipes spanning the range of human hearing (20 Hz to 20 kHz), what would be the range of the lengths of pipes required) pdr 7-jzw-qtfzc93 t? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

  A tight guitar string has a frequeg)/ 1n xlvtvj*ncy of 540 Hz as its third harmonic. What will be its fundamental frequency if it is fingered at a length of only 60% of its original lenntgvv 1x*/) ljgth?   Hz

  An unfingered guitar string is 0.737:-nxpf nj; rt2yi2 kc m long and is tuned to play E above middle C (330 nt2c;:2xf iry-n p7jk 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 m0az b j)o;tvwb2q j:f pxfcgp + 71)gff3-ht9diddle C (262 Hz) when the temperature is fjgx7d ba 9tw3ofczf q- +b1p0 f;)hg:ptv)2j 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 hf:/2 (mgbjfsjwfe 37at 20 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece of the flute in El-k8i6 e0 h.m )boptplxample 12–10 should the hole be that must be lh) t6-.oi0k pb eplm8uncovered to play D above middle C at 294 Hz?    m

  (a) At T = 20 $^{\circ} $C how long must an open organ pipe be to have a fundamental frequency of 294 Hz?    m
(b) If this pipe is filled with helium, what is its fundamental frequency?   Hz

  A particular organ pipe can resonate at 264 Hz, 440 Hz, and 616 Hz, iu5m42xvzf7 tzyzj4- but not at any 2i-5 4ft4u7zyxjvmz z other frequencies 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.wesoa eo iguw*6 *+ppcs+.3d,80 m long is open at both ends. It resonates at two succ .co6 dsp3,giap +*wueosw*e +essive harmonics 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 .lyvc p;p : dul2n b3i7m8e 0fgc+v3xz$^{\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 by09ox:tfhem6iws7 8 the audible range for a 2.14-m-long organ pipe at 20 oeim97h68bf:xwsyt 0 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is jgwvi* ucnof7 b+h(69 approximately 2.5 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 stanh6(7iu 9w+bjn*ov cfgding 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 fpc.-2 pqjt ujph7, -*rm;wr*v 5pz dls when trying to adjust two strings, one of which is soupft h, lr5v2d-zq.prpc;jj w* -7*pmunding 440 Hz. How far off in frequency is the other string? ±    Hz

  What is the beat frequency if middle eycqvjwkvu+y p*2-5z 49js 5xC (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 kHz4aqr bvd 7 ezn0gsko:e py;/)+, 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 simultaneo pbaq/nge)r;zsek0:v 7 4o+ydusly, estimate the operating frequency of brand X.    kHz

  A guitar string produces 4 d-dw1he7nwt 8beats/s when sounded with a 350-Hz tuning fork and 9 beats/s when sounded with a 355-Hz tuning fork. What is th7t1wwnhde d -8e vibrational frequency of the string? Explain your reasoning.    Hz

  Two violin strings are tuned to the same frequency, 294 Hz. The zvkh+mqdm0)9tv 6 8s ltension in one string is then decreased by 2.0%. What will be the beat frequency heard when the two strings are played together? [Hint: hqms) 80t+l v9zkv6mdRecall Eq. 11–13.]    Hz

  How many beats will be heard if two identical flutes each try y*p.a n ssz7ik*cuf66b1sa 7u to play middle C (262 Hz), f nskyip*u b6*acs 1s.z 677aubut one is at 5.0°C and the other at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks, A, B, and C. For qmk je;:xg6,ik B has a frequency of 441 Hz; when A and B are sounded together, a beat frequency of 3 Hz is heard. When B and C are so6q,ie:mxgk ; junded 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 p (g :eqbu-hz0ehl ;4jm from one speaker and 3.50 m from the other(zhb - jple ;g:h0ueq4.
(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 hearbu,ihhv7g hc)rnv-h/ uel 6s+/-*ipis three beats every 2.0 s when they are played trg+i/v hh 6psch- *,lbiuv)-uie7 /hnogether. (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 1fszy+ 6s q*9upo 6h6ckzr2nland 2.76 m in air. How many beats per second will b nhpl6k+6usr6 o2qz sycf*91ze heard? (Assume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain fire engine’s siren isr6 1ujz)(bacu 1550 Hz when at rest. What frequency do you djuu)1bzrca (6 etect 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 firnd9 ia0jw+,gu e engine whose siren emits at 1550 Hz moves at a speed of d 0n9ag,w iju+32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift k4cgt kc4u()m; a78azrvl ;:mlosqs; in frequency if a 2000-Hz source is moving toward you at 15 m/s versus you moving toward it at 15 m/s Are the two fre clg;;4aumkqz:)(7lka tc4 s vo;msr 8quencies 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. Wheicm ncqj ;(.*emfg.uy)2ft p;.et0den one is at rest and the other is moving toward the first at 15 m/s the driver at rest hears a beat frequency of 5.5 Hz. What is the frequency the horns emit? Assume Tt2iut. 0ecy.e;qpj cfm) mdf. e;gn*( = 20 $^{\circ} $C    Hz

  A bat at rest sends out ultrasonic sound+h f* :ey h0phh8lcva/jo,)zc 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 frequencfh h/cpho)a e+*hz,cj08v: yly?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a sy lu;db d3q)jc:)hr 1ypeed of 5 m/s As it flies, the bat emits an ultrasonic sound wave bdyu3 yqdc 1j):)hrl;with frequency 30.0 kHz. What frequency does the bat hear in the reflected wave?    $ \times10^{4}$ Hz

  In one of the original Dopp7oqg+b a-*crd- zwr75m 8,o(h w qzswdler experiments, a tuba was played on a moving flat train car at a frequency of 75 Hz, and a second identical tuba played the same tone while at rest in the railway station. What beat frequency was heard if the train car approached the station at a speed of 10z-7q8o 7r-d bh,m arosczdgw( *q5+ww m/s ?   Hz

  A Doppler flow meter uses ultrasound waves to measure blood-flow speeds. )nd9m(,ef+2wd :ci u,bvvivuSuppose the device emits sound at 3.5 vv(9iucv ,) if+ub w2n:,eddmMHz, 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 ultrasonic wav 8,5q wqggrp+s kavup+b ;2z3jes 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 so1 d)q2p xjo9 w1v4bukg crf)n*und of frequency 570 Hz. When the wind velocity is 12 m/s from the 1vw4*pknqf x9 o1jg)c bdr) u2north, what frequency will observers hear who are located, at rest,
(a) due north,   Hz
(b) due south,   Hz
(c) due east,    Hz
(d) due west, of the whistle? What frequency is heard by a cyclist heading    Hz
(e) north    Hz
(f) west, toward the whistle at 15 m/s?   Hz
Assume T = 20 $^{\circ} $C

  How fast is an objecu :z bn4i.)o ;ze7 xg 9gbnlvxlbg-) 8.uvjmy4t moving on land 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 speed of sound is 310 m/s3(i;tj;qd5 n xqwy qk9d. fczpa*4.as (a) What is the angle the a5ka(zw.xp;q ;jd di3f .sy49t*c n qqshock 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 pn 0dl-0(p;:lfwue abqlanet where the speed of sound is:lwd-; (paul0f0bq n e 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 ocean. Determinn ,m3)0fjktar e the shock wave angle it produces m kf0tr),ja3 n
(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 ou(3 zb.cur-a6 .ld ru$/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly ove, zz (zbses ir+ )cv9k,)jq3jdrhead and see a 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. eis)q,3jb(cr dk)+zz j, vsz9See 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 s 15 8e se u)lsnop+0llti),ugvends 20,000-Hz sound pulses downward from the bottom onlu, tsilevls) o801pu+ 5g) ef 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 pulses (in fresh water)?    s

  Approximately how many octaves are therag+ zz/+gnxcnvc 5:n2e in the human audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display calledpax6 dajb) q;- .r9eth a sewer pipe symphony. It consists of many dq bxj9th).e-pa6a; r plastic pipes 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 cl5nq5:xcul gp8 f njf*a69:nugose to the threshold of human hearing (0 dB). What will be the soufgg*: aj u5nln9n6u8cx 5qp:fnd level of 1000 such mosquitoes?    dB

  What is the resultant sound level when an 82-dB sound 1xn-.dp )eqyba)yd4sand an 87-dB sound are heard sidyaqsp dy)xe n.4b1 -)multaneously?    dB

  The sound level 12.0 m from a louq zl +m kc*vcx-s7 *ycdh932stdspeaker, placed in the open, is 105 dB. What is the acoustic power output (W) of the speaker, assuming it radiates equally in allcx 73 *myq+s *-vhc9k tlsdzc2 directions?    W

  A stereo amplifier is rated at 150 W output at 1000 Hz. - b +cob x,-a6ny*nzqiThe power output drops by 10 dB at 15 kHz. Whaab+ q no,*by -c6z-inxt is the power output in watts at 15 kHz?    dB

  Workers around jet aircraft type1zkjc+1md,hh ux):qtj; j5* sm 7ig sically wear protective devices over their ears. Assume that the sound leg jm5j+ kjz1uqsms:1 c,e)*h7;xti dhvel of a jet airplane engine, at a distance of 30 m, is 140 dB, and that the average human ear has an effective radius of 2.0 cm. What would be the power intercepted by an unprotected ear at a distance of 30 m from a jet airplane engine?    W

  In audio and communications systems, therag 6t) 6*7,dfi ogipp 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 1zgkn*:s+ kki0j+ 3opb $\frac{1}{2}$ 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 2f2iiybggo je5p m h/;hq w.86long between fixed points with a fundamental frequency of 440 Hz and a mass per unit lengthphq . h2bijo g25;gmefi wy/86 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 (wzdv4/,bv1grrczy).u n;8:m o x n ih2bbaw2 vibration above a vertical open tube 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 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 fg wnz81oix) :dn2w.z(/hbvc;abuy4br mr,2v requency of the tuning fork?   Hz

  A 75-cm-long guitar string of mass 2.10 g is near a tube that is open at olz( 3 nyp98,zho3tsd et2a9jr.y4knlne end and also 75 cm long. How much tension should be in the string if it is to produce resyd (sh4tla.zo38j kply 9 terz ,93nn2onance (in its fundamental mode) with the third harmonic in the tube?    $ \times10^{ 2}$ N

A highway overpass was obser 0xd-gzu1 uv6 2,lkei eiwaj7+bfq-7yved 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 j4k/vvw (pirg): /fdztone 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 persofz dj4/ w:pirg /v()kvn 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. Ohmcjatr(xs s ;ks1m;1- mg 8/sne train is stationary. The conductor on the stationary train hears a 3.0-Hhs( s/gsxams;1; 1tj-rm8mck z beat frequency when the other train approaches. What is the speed of the moving train?   m/s

  The frequency of a steamgap-+ /b ij0ulcy15jicf3me 8z 7e.uytsw *5m train whistle as it approaches you is 538 Hz. After it passes you, its frequency is measured as 486 Hz. How fast mu*ys5pay+0iw ejg17 i j em5-/3u8cb tlz.cfwas the train moving (assume constant velocity)?    m/s

  At a race track, you can 4zy7ov k;:hf5 w1ksyaestimate the speed of cars just by listening to the difference 7o kfwkz1;:h 5aysv4 yin pitch of the engine noise between approaching and receding cars. Suppose the sound of a certain car drops by a full octave (frequency halved) as it goes by on the straightaway. How fast is it going?    m/s

  Two open organ pipes, sounding together, produce a ctb(0*f8 ov .vu0ibzlw;wa*d beat frequency of 11 Hz. The shorter one is 2.40 m long. How ll*a o 0w fbbz8tv.d;0*iw uc(vong is the other?    m

Two loudspeakers are at opposite ends of a railrl8z gz+i2l: saoad car as it moves past a stationary observer at 10 m/s as shown in Fig. 12–37. If the speakers have identical sound frequencies of 212 Hz, what is the beat frequency heard by the observer when (a) he listens from the position Aa8+:il 2sz gzl, 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 sj)x) 3t pbwm6in the aorta is normally about 0.32 m/s what beat frequency would you expect if 5.50-MHz ultrasound waves were directed along the flow and reflected from the red blood cells? Assumsj)bw3m x)6pte that the waves travel with a speed of $1.54 \times10^{3 }$ m/s   $ \times10^{3 }$Hz

  A bat flies toward a moth at speed 6.5 m/s while the ( cjp6zdbq q0:moth is flying toward the bat at speed 5 m/s The bat emits a sound wave of 51.35 kHz. What is the freqjpz6(cd q0b:q uency of the wave detected by the bat after that wave reflects off the moth?    kHz

  A bat emits a series of high frequency sound pulses as it approaches a moth.//;dbdz*h.vq+ cb(c ied f hv, 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 fro,vhbbz*;i+ ch( vcd./f/ddeqm one chirp returns before the next chirp is emitted?    m

The “alpenhorn” (Fig. 12–38) was once used to send signals from onei r:,ujex g52p Alpine village to another. Since epj:2ix gu,5rlower 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.) Model as an open tube.

  Room acoustics for stereo listening can be compromised by the presence of 1 g.o+ 6tfjhfmho0 et2standing waves, which cthf2f te+o.h1j 0gmo6an cause acoustic “dead spots” at the locations of the pressure nodes. Consider a living room 5.0 m long, 4.0 m wide, and 2.8 m high. Calculate the fundamental frequencies for the standing waves in this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

  A dramatic demonstration, called “singing 42. k*niaw y9ybtybs(rods,” involves a long, slender aluminum rodby ybi (*2 ya9w.4kstn 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 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 ofgy 1eqj6i/dia .5a7fx2tr c )m hearing for the human ear at a frequency of about 10007yfg2 16m aredta/xc)qi .ji5 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 )ws, (4nx6;uq),m ygg jpf ibrmklj6 4the sonic boom 1.5 min qg4 iwspm k) myuj,(6 )rgbl,4njx6;fafter the plane passes directly overhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboat5e,wznd e6ck)tf es80:e y)yl 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