What is the evidence0 *otupzcd2-d lzmq+x.+y + fn that sound travels as a wave?

What is the evidence t/o aun,; zlzr+hat sound is a form of energy?

Children sometimes play with a homemade “telew5 2:bgf/q:cmsf m pjs r617mrphone” by attaching a string 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 cup (Fig. 12–29). Explain clearly how the sound wave travels from one cup tmf2rm:w76:f5qb s/1m p jscr go the other.

When a sound wave passes from air into water, do you expect the frimwh iy*c:,hd x5;5 yrequency or wavelchyy dh5iwim;x ,5*r :ength to change?

What evidence can you give that the speed of sound in air does not depend sa4e)sh 7qi 7r* icb32ixg:ofbignifixbeg ibf)3 c2r s*ah:qo4i 77icantly on frequency?

The voice of a person who has inhaled helium s)8kz6e/wpd :gq60t fxgeh: suounds very high-pitched. Why?

How will the air temperature in a room affect the pijgl4. aokx3o 35u86uyerr9yul3 5a khtch of organ pipes?

Explain how a tube might be used as a filter to reduce the amplitude of skkfd r/3v :hb8ounds in various frequency ranges. (An example is a c3kfh kv/d:rb 8ar muffler.)

Why are the frets on a guitar (Fig. 12–30) spaced clo+2nea 85fe6w2 f9atreq;f nttm cq -t*ser together as you move up thfm9f wa2ne* a 6c+ent 52t-r8ttfqq e;e fingerboard toward the bridge?

A noisy truck approaches you fqh8dqg 3,kdc7rom behind a building. Initially you hear it but cannot see it. When it emerges and you do see it, its sound is suddenly “brighter” — you hear more of the high-frequency noise. Explain. [Hint: See Secti ,q78 dhd3kcgqon 11–15 on diffraction.]

Standing waves can be said to be due to “interference in space,” whereas betf kv+wyk;..d ats can be said to be due to “interference in time.” Evk;yf.kt +wd. xplain.

In Fig. 12–16, if the frequency of the speakers were l yl1f a9.u)xxaowered, would the points D and C (where destructive and constructive interference occur) move farther apart or closer togla 9au)x. fyx1ether?

Traditional methods oftrb +-p df y/q2iepd/) protecting 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/d)ieypbd+f-t/r 2 q p. 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. 64g/nhyy+ccgEach 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) or4gc /hyncy6g+ (b), are the two component frequencies farther apart? Explain.
(12-31)
(12-18)

Is there a Doppler shift if the sourc(o gta7o* k/uwe and observer move in the same direction, with the same ve/gou(* 7 otwkalocity? Explain.

If a wind is blowing, as h,w upvk4+s8-(n1,ni nrzewill this alter the frequency of the sound heard by a person at rest with respec(+,e s ns upk-1z48nrvwi,nah t to the source? Is the wavelength or velocity changed?

Figure 12–32 shows various positioy64svfwc s94q k:;vy6a ,fn gvns 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 hea :ygcvqfvn sv;,f4wy6 9s64akr the highest frequency for the sound of the whistle? Explain your reasoning.

  A hiker determines the length of a lake by list4vp)3 xzg/yx( ksybr)euu p; 5ening for the echo of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.0 s aftep kx4v; r)z/e 3yuy u)bgs(5pxr shouting. Estimate the length of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship just below the watewd ++ol)fphsg+/f 8+m *ujkqgrline. He hears the echo of the sound reflected from the ocean floor directly below 2.5 s later. How deep is the ocean at this point? Assume the speed of sound in seawater is 1560 m/s (Table 12–1) and does not vary significant gmho)dfkp+s l+g+f8/*j w+q uly with depth.    $ \times10^{ 3}$m

  (a) Calculate the wavelengths in aihl jfj q+r;8r4 ni qc)/kgk;(2en b2jar 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 abb4u6bh73 nav nd2bv 3kove a school of tuna on a foggy day. Without warning, an engine backfire occurs on another boat 1.0 km away (Fd ahb bk63b43 v7nunv2ig. 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 7ahyc1 b. pef-a;-uk ,p/lvjt when striking the water bep7lfa h -y.j ;/uacke,v-p1 btlow is heard 3.5 s later. How high is the cliff?    m

  A person, with his ear to the ground, sees a 8efausrgrq48l7:(br huge stone strike the concrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other in the concrete, and theyegb4f87(sa : rrr8lqu 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 oney yzy5f:8wl +y)ka1meepn)nt q2ux0 , mile of distance by the “5-second rule” for estimating the distance from a lightne ,q)muktyfe)nlywzpy2 y ax510 +:n8 ing strike if the temperature is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity of a sound ah,y3bvhlsd u79znlp/, 9b q(u / ;fxmst 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.dy: r dmc+z cyyk7/h7d whose intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound lema/ r*pc5t.oo vel of 95 dB when fired simultaneously at a certain place, what will be the sound level if only one is exploded? [Hint: Add intensities, no. *mc/rpotoa 5t dB’s.]    dB

  A person standing a certau*ttwi0 y8el;in distance from an airplane with four equally noisy jet engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person experience iyut;it8w el *0f the captain shut down all but one engine? [Hint: Add intensities, not dB’s.]    dB

  A cassette player is said to have a signalgk;( xwjz ct+,ur0-lo-to-noise ratio of 58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensities of the signal and the backgro( + ;oxt-rz, uwkjgcl0und noise for each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of zb d/.ialpr.mddx+0b9 o.6bvsound from a person speaking in normal conversation. U.b .i+d6bdol./9 dbzr mpax0vse Table 12–2. Assume the sound spreads roughly uniformly over a sphere centered on the mouth. $\approx$    $ \times10^{ -6}$W(Round to the nearest integer)
(b) How many people would it take to produce a total sound output of 100 W of ordinary conversation? [Hint: Add intensities, not dB’s.]$\approx$    $ \times10^{7}$people

  A 50-dB sound wave stri cu-oyl3 (r,ehr1-kogkes an eardrum whose area is $5 \times10^{ -5} m^2$ (a) How much energy is absorbed by the eardrum per second?    $ \times10^{-12}$W (b) At this rate, how long would it take your eardrum to receive a total energy of 1.0 J?   $ \times10^{ 3}$yr

  Expensive amplifier A is rated at 250 W, while the more modevygk94jg* ).)hfpixd st amplifier B is rated f )).v 4gxik 9gdphj*yat 40 W. (a) Estimate the sound 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 meter registered jypt:y *jf6 n6130 dB when placed 2.8 m in front of a loudspeaker on the stage. nj6 :typjy*f6
(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 v2o52 qs gwfz(9wdd/cin sound level of 2.0 dB. What is the ratio of the amplitudes of two sounds whose d9dcq52/ fzwsw v2 o(glevels differ by this amount? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound wave is tripled, (a) by what factor wxunz+h(r,j;ticr:zi sl8 ,h 1ill the intensity increase? Increase by a factor olh,iczsr; +8 jx1inr(h z: t,uf    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal displacem i-lt.ng6miif3c2eo9ent amplitudes, but one has twice the frequency of the other. What is the ratio of their in 6il29-ic ft imgneo3.tensities?   

  What would be the sound lev s;g-dcb.n6xo el (in dB) of a sound wave in air that corresponds to a displacement amplitude of vibrating air molecules of 0.136oc.snb -g d;x mm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level to seem +jes a,j+ 1ntbas loud as a 100-Hz tone that has a 50-dB so1,jsaj b+n e+tund level? (See Fig. 12–6.)    dB

What are the lowest and highest frequencies that an; os rlau.jfx4 -qi(-e ear can detect when the sound level is 30 dB? (See Fig. 14;r oe aj (uixl-qsf-.2–6.)

  Your auditory system can accommodate a ui. acpc5:u5ohuge range of sound levels. What is the ratio of highest to lowu.oa :u5p5 cicest 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 fr:y9*;koycu5x)qwp;vff,u j/ xl :emp equency of 440 Hz. The length of the vibrating portion isyvm, 5jf: x;f9;k wpq*y /xu)o:leucp 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 cm5fk) dl2gn(r n long. What are the fundamental and first three audible overtones 2fl 5kr)d(gnnif 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 frequ5deovj:nw x f80pj*-t+e vw0awh3b(n ency would you expect from blowing across the top of an empty soda bottle that is 18 cm deep, if you assumed it wap8nen:t w-00b+j *w wvhfea(ov53x d js 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-tube pipq4 bco:zrre42 es spanning the range of human hearing4 :r2qebo c4rz (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 /vh:wu w l+6la kbv9 jkr81(pwa frequency of 540 Hz as its third harmonic. What will be its fundamental frequency if it is fingerwa +jrw8l1h klwu6 b(/v:vp 9ked at a length of only 60% of its original length?   Hz

  An unfingered guitar string is 0.73 m long and is tuned to 2lp u m67y cr3xw(xmu3play E above middle C (330 Hz)cy7xw 3ulu6p x(mm32r.
(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 middle C v.-ggfcw1rv* (262 Hz) when the te.gvwgc r-*v 1fmperature 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 2039c re,gcwjf)w2 nlf8 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the moute 5r ;qp36(t;ygh cza;d c8d uw9 k6bf,wtgga-hpiece of the flute in Example 12–10 should the hole be that must be uncovered to pl3 qpw(u-5 ;d9atggg,bw;hcfa ky8;6dre t6 zc ay 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,)))kp holpkir,vpgp k s8)4x ( but not at any other frequencies in between. (a) Show why this is an open or a pkg) (8k,s rx)i) k)vp4opplh closed pipe. ----待选择----closedopen  (b) What is the fundamental frequency of this pipe?   Hz

  A uniform narrow tube bp.2 *bob : wfg kufi8lkj)g-+1.80 m long is open at both ends. It resonates at two successive harmonics of frequencies 275 Hz and 330 Hz. Whb+wbfpjli*kgf- 2bkgu):. 8 oat 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 ajo9465cpq p c99.jqzvz pq n,$^{\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 presen20ep :pqkp3t*tfw: hit within the audible range for a 2.14-m-long organ pipe at 2tw0f2pi:*k3tp h:eqp0 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approxi9 flhf)ugb)+a h/5s yemately 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 standing waves in the ear canal. 5afug hybs9/l)h+ f )eWhat 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 2i-h yj c6rngv:jq/q8 * uqzby-xi8 g:when trying to adjust two strings, one of which is sounding 440 Hz. How qrhjv6gz:ix:*-iy-gjub 8cy/2n qq8 far off in frequency is the other string? ±    Hz

  What is the beat frequency if middj4) faq w 93gkctip7z0le C (262 Hz) and $C^＃$ (277 Hz) are played together?    Hz What if each is played two octaves lower (each frequency reduced by a factor of 4)? $\approx$    Hz

  A certain dog whistle operates at 23.5 kHz, while another (brand X) operates6+ nb *.flhc j5iuupge1 j+hv- 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 n fv j1+h+l6.*g bh5ijcep uu-they are played simultaneously, estimate the operating frequency of brand X.    kHz

  A guitar string produces 4 beats/s when sounded with a 350-Hme4d1 cfy :a,/rrhv u:z tuning fork and 9 beats/s when sounded with a 355-Hz tuning fork. What is the vibrational frequency of the string? Explah4 r f,ce/:ad1vuyrm: in your reasoning.    Hz

  Two violin strings are tuned to the same frequcd;b44vffi 84,r dh bvency, 294 Hz. The tension in one string is then decreased by 2.0%. What will be the beat frequen4f f8bd4 i ,4rhv;vbdccy heard when the two strings are played together? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be heard if two identical flutes each try gbof1x/cdbo3 n 9:wm 1to play middle C (262 Hz), but one is at 5.0°Cfdgb93wo1nm 1/x b oc: and the other at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks, A, B, and C. Fork zhgb/(4iwl( y 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 sounded together, the bebg /zi( y4l(what 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 stan 8qw hw seo4f7(1 x8fgi4ko7cpds 3.00 m from one speaker and 3.50 8eo cgs17fq wxh7o (4wi4f8pkm 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 a;k ms3f+(uczys/tk.z u0l- 5w 3 ouskct 132 Hz, but a piano tuner hears three beats every 2.0 s when they are played together. (a) If one is vibrating at 132 Hz, what mumoc u kk zuzt+ycl3;s3/-0 5k(wsu.f sst 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 mked w+ )2 h9xiafj7i*b and 2.76 m in air. How many beats per second will be7jk9ab dewi+ih* f) 2x heard? (Assume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain fire engin3k8a+c-qz04i k 9pk0uomks zxe’s siren is 1550 Hz when at rest. What frequency do you detect if you move with a pkm-osx3kk zz0 4 0 9cqak+8iuspeed 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 enginkae80x/c g2qfe whose siren emits at 1550 Hz moves at a speed of 32 m/s a0 8eg2k xf/cq
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift in frequency if anw1bx4 xw )f 1oy;gn/o 2000-Hz source is moving toward you at 15 m/s versus you moving toward it at 15 m/s Are the two frequencies exactly the same? Are the/nxn wx)1 ooyg1 w;bf4y 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 wic)p sm 5 q6ei rjdc0r1 3r;isp)ian,w-th the same single frequency horn. When one is at rest and the other is moving toward the first at 15 m/s the driver at rest hears a beat frequency of 5.5 Hz. What is the frequency the horns emit? Asw smpri)dsri a53q;,j n0 cpc6r1 i-)esume T = 20 $^{\circ} $C    Hz

  A bat at rest sends out ultrasonic sound waves at 50.0 kHz andn, ;o 1cqx rrbpdps44; receives them returned from an object moving directly away from it at 25 m/s What is the q;s d1pr4b ,r;4pnxocreceived sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed of 5 m/s As it flies, the bat n cj(l(xq( 5dremits an ultrasonic sound wave with frequency 30.0 kHz. lq(n 5rcdj((x What frequency does the bat hear in the reflected wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experiments,ns*fgfm( 0jr3 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 rm3j nf gf*r0(sest 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 *iyd,, ctsgw1 waves to measure blood-flow speeds. Suppose the device emits sound at 3.5 MHz, and the speed of sound in human tissue is taken to be 1540 m/s What is the expected beat frequency if blood is flowing in large leg arteries at 2 cm/s dii,,y*1g c wstdrectly away from the sound source?   Hz

  The Doppler effect using uzt x28vaz1/wi *-ln. gc c7pekltrasonic waves of frequency $2.25 \times10^{ 6}$Hz is used to monitor the heartbeat of a fetus. A (maximum) beat frequency of 500 Hz is observed. Assuming that the speed of sound in tissue is $1.54 \times10^{3 }$ m/s calculate the maximum velocity of the surface of the beating heart.    m/s

  A factory whistle emits sound of frequency 570 Hz. When the winnc / fl83 bd-m3ahx7 ,:yppuird velocity is 12 m/s from the north, what frequency will observers hear who 3fryxb7/-ic pal3p8mn,u :hdare 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 speed at 2 / /48dcpric3out czstj(i (t90 $^{\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) What7k1z*d j9h2 lyijf1lt is the angle the shock wave makeskd z7hy*l2fli11t jj9 with the direction of the airplane’s motion?    $^{\circ} $
(b) If the plane is flying at a height of 7100 m, how long after it is directly overhead will a person on the ground hear the shock wave? $\approx$    s (Round to the nearest integer)

  A space probe enters the thin atmosphere of a planet where t2ld8n2djbtb tons*4,he speed of sound is only asto4*bb lt8,2n2ddjnbout 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. Deter,;h:hn ti x;-,v obevim7f-dcmine the shock wave angle it c-x-hfi dtv me;;,, i vonb7h:produces
(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 477 uvo6(ned / h- y1ntpiiuci$/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly overhead and seep161d lng lb2x 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. Seb6px112 dln gle 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 supvelv3zf j vgu -f6 6vdp3m m,1,d0gx 3cub:6ends 20,000-Hz sound pulses downward from the bottom of the boat, and then detects echoes. If the maximum 3guz-1vmpcu j ,ve,fuxbd:63gvd6f l0v 6 p m3depth for which it is designed to work is 200 m, what is the minimum time between pulses (in fresh water)?    s

  Approximately how many octave lz 87pic8ocvbx2 0koy;bn1z*5 f 0viv2cmf5fs are there in the human audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display called a sewer pipe l nv ks ,s;(l5 r)uoo)s r7ye/onw9/ftsymphony. It consists of manyrs f,)v(u7o lo k/;nnsw / r)yloe5ts9 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 mavy74u rbo/8-objdt r:kes a sound close to the threshold of human hearing (0 dB). What will be the souno-o4v dytb:/u 7jrr 8bd level of 1000 such mosquitoes?    dB

  What is the resultant sound level when an 82-dB sound and an 87- 2qzn48car 2sudB sound are heard simulc2 84rn2zsaq utaneously?    dB

  The sound level 12.0 m from a loudspeaker, placed in thepwm0peo7 qos zz2 39x6 open, is 105 dB. What is the acoustic power output (W) of thwzopp2 7sx906zq em3oe speaker, assuming it radiates equally in all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 Hz. The power output drops s8 cari:, dn+sy2d: nu-v flq.by 10 idyl+:n fn uqs ds.2rac-8v,: dB at 15 kHz. What is the power output in watts at 15 kHz?    dB

  Workers around jet airw lpt frf(-+n,z-2a:+ uvzharcraft typically wear protective devices over their ears. Assume that the sound level of a jet airplane engine, at a distance of 30 m, is 140 dB, and that the average human ear has an effective radius of 2.0 cm. What would be the power intercepfvn(+: -rwztazl-+ap,2 rfhuted by an unprotected ear at a distance of 30 m from a jet airplane engine?    W

  In audio and communications systems, the gain, fsnlqc7:0b zlj7)4 wi1 if c1nqn;ti 6$\beta$ 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 tune *;, jfspmpjqvyz 614ld to a frequency 1$\frac{1}{2}$ times that of its neighbor. The four equal-length strings are to be placed under the same tension; what must be the mass per unit length of each string relative to that of the lowest string?
$f_{A}$ =    $\mu_{A}$
$f_{B}$ =    $\mu_{A}$
$f_{C}$ =    $\mu_{A}$

  The A string of a violin is 32 cm long between fixed points10 q rqi*lz::(tqob gx with a fundamental frequency oqt1:rxq*( i0zql:bg 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 verti a1z5-v4syyg, s pbgh8cal open tube filled with water (Fig. 12–35). Thes -y a,ph4sz1v85yb gg water level is allowed to drop slowly. As it does so, the air in the tube above the water level is heard to resonate with the tuning fork when the distance from the tube opening to the water level is 0.125 m and again at 0.395 m. What is the frequency of the tuning fork?   Hz

  A 75-cm-long guitar stry*1t8wpwmb 9px m0:gy ing of mass 2.10 g is near a tube that is open at one end and also 75 cm loywgm19:* ppw yt0b8xmng. 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 on;.6dmgld.q rie 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 range cor p(ze owj;5c4ming from two sources. The sound is loudest at points equidistant from the two sources. To determine exactly what the frequency is, the person moves about and finds t o4(ecwj;5z rphat 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 whistixo 0c:)-tgdples. One train is stationary. The conductor on the stationary train hears a 3.0-Hz beat frequency when the othd-pgt)c 0xoi:er train approaches. What is the speed of the moving train?   m/s

  The frequency of a steam train whistle as vo(m1 s.xakm, )i(7gxo9 xc riyd9sg0it approaches you is 538 Hz. After it passes you, its frequency is measured as 486 Hz. How fast was the train moving (assume constant veloci9srgk)g.o yimx,m xdv7o 0 c9x1ai(s(ty)?    m/s

  At a race track, you can estimate rc9.:nx5vu w lthe speed of cars just by listening to the difference in pitch of the engine noise betw5cn:rvu x .lw9een 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 beat frequencbay3dam; v: :vy of 11 Hz. The short:va b:v3 myd;aer one is 2.40 m long. How long is the other?    m

Two loudspeakers are at opposite ends off e04ywg(u7vw a railroad 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) 4fvyw0egwu (7he listens from the position A, in front of the car, (b) he is between the speakers, at B, and (c) he hears the speakers after they have passed him, at C?

  If the velocity of blood flow in the byl49/ qy 4gdyaorta 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 b9/yq4gd yyl4 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/s while the moth is flying towa oyoi-5;mh44wg)j yy zrd the bat at speed 5 m/s The bat emits a sound wave of 51.35 kHz. What is the frequency of thoywy ;zogm4y i-4) j5he wave detected by the bat after that wave reflects off the moth?    kHz

  A bat emits a series of high frequency sound pulses kj41hke.cuh8 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 hh8uc.j 4 kek1be detected by the bat so that the echo from one chirp returns before the next chirp is emitted?    m

The “alpenhorn” (Fig. 12–38) was once used ton 0l a z,a4r3apo)1bvj 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 horj1 a4 0lrzpb)3a,navo n, 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 presencehl 0r (mvk;bgrcy( v;0 of standing waves, which can cause acoustic “dead spots” at the loca(kr yr (;mcg0h;lvv0b tions 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 rods,” involves a long, slenderkcx ne,0 rer37 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 “sr07 3 ,cenkxreing,” or emit a clear, loud, ringing sound. For a 90-cm-long rod,
(a) what is the fundamental frequency of the sound?    $ \times10^{ 3}$ Hz
(b) What is its wavelength in the rod,    m
(c) what is the traveling wavelength in air at 20 $^{\circ} $ C?    m

  The intensity at the threshold of hearing for the human ear at a frequen-ufe.yqnc8 mbrbv/58 q46q hz cy of about 1000 Hzc8 r6nbq z4mfb8.-5/hey vq uq 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 2.0cqonwp*0l+ s 4. An observer on the ground hears the sonic boom 1.5 m so pncl+4w*0qin after the plane passes directly overhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboatz yt wfp7wu.azai-50- 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