What is the evidence that s -:llrdae .*/kuh*rzf/f5i6 fhw2qw h ound travels as a wave?

What is the evidencev jkv4wl/6ef c.5ag8e that sound is a form of energy?

Children sometimes play with a homemade “telephone” by attaching a string to thpdc(m8 noj,. ys, 9i 8q +a7kkjfc1njxe bottoms of two paper cups. When the string is stretched and a child speaks into one cup, the sound can be heardkj,,x c8kymj8po c +injf(dq7an1. 9s 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 a*mnax4 qdp tda48--icir into water, do you expect the frequency or wavelengxcitq dd pm8a*n-4a -4th to change?

What evidence can you give0t4vw r w xgkrqwk930p5m)s(t that the speed of sound in air does not depend significaqr k 0p wxt)(490 wvtmsgk3rw5ntly on frequency?

The voice of a person who has inhaled helium stg l( e uxxwxlq.58*9sounds very high-pitched. Why?

How will the air temperature in a room affect t6jo ehwz y( 9j.goume*2 nsbz3/4wzen iv5-x5he pitch of organ pipes?

Explain how a tube might be used as a filter to reduce the amplitude oflz-aov4ns0g t mlp5u8q r ;30 lgdi1l7 sounds in various frequency ranges. (An exad7 n lual0o;3zq1gl4it vp msg5 lr08-mple is a car muffler.)

Why are the frets on a guitar (Fig. 12–30) spaced clozlz jjm2g9 3:(;0nhij ;jbdddser together as you move up the fingerboard toward the m0z2g; dnj9j3h:jj ldzd;b(ibridge?

A noisy truck approaches you from bels,,: pjc s8dw.vhd)r hind 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. Explaid rdc) ljv :8sp,sw,h.n. [Hint: See Section 11–15 on diffraction.]

Standing waves can be said to be due to “interfereny xsto,5 ee()sce in space,” whereas beats can be said to be due to “interference in time.” Exx 5)y sese,(otplain.

In Fig. 12–16, if the frequency of the speakers were lo+ w9l(jmvb .zy+ yf/u.tg vvm;wered, would the points D and C (where destructive and co .m+lz9ut; gvv(+y jwvybfm/.nstructive interference occur) move farther apart or closer together?

Traditional methods ovmby cak+*9wbo(st p0t r p04-f 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. Instead, a device is used which detects the noise, inverts it electronically, then feeds it to the headphones in t0+pwmk49b-0ta( c*byvspr o 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. Each wave can be tq1su:(faw 8d8pgfx1 ghought of as a superpow 8g1 gaq(f1 8ufdpx:ssition 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 frequencies farther apart? Explain.
(12-31)
(12-18)

Is there a Doppler shift if the source jmhs;r*7en7p s1 )uf oand observer move in the same direction, with the same velocity? Expl;nshrs*j )ouf7 m1 7peain.

If a wind is blowing, will this alter the frequenoka1-a(zd2 md,q*k os cy of the sound heard by a person at rest with respect to the source? Is the wavelength or velo2ddaaoz1 -( o,k*ksqm city changed?

Figure 12–32 shows various positions of a child in motion on a swing. A monitor hp+u7 qve si9,is blowing a whistle in front of the child on the ground. At which position, A through E, will the child hear the highest frequency for the s,s 9i+q7eh puvound of the whistle? Explain your reasoning.

  A hiker determines the length of p6df(d s rb.t+a lake by listening for the echo of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.0 s after shouting. Ed+rp 6 bs.(dftstimate the length of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship * vx9f23zlyop g*g fx0just below the waterline. He hears the echo of the sound reflected from the ocean floor directly belo 9fz3gxlgf*2 *x0pvy ow 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 wavele)k dww9b/* tdi5 nhik-ngths in air at 20 $^{\circ} $ C for sounds in the maximum range of human hearing, 20 Hz to 20,000 Hz. $\lambda_{20Hz}$ =    m $\lambda_{20kHz}$ =    $ \times10^{-2 }$ m(b) What is the wavelength of a 10-MHz ultrasonic wave?    $ \times10^{ -5}$m

  An ocean fishing boat is drifting just above a school qo f*do1ysi2z( vs/;gq d9j5sof tuna on a foggy day. Without warning, an engine backq ;vq*zd1(ids5sj fo2oy /s9 gfire occurs 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 striking t+ud3g+ h 2suz;chfpp-he water below is heard 3.5 s later. How high is the clihgfpz;d +u3-c2+ uh psff?    m

  A person, with his ear to the ground, sees a huge stone strike the concrete pave. d)gr kz5ph:bment. A moment later two sounds are heard from the impact: one travelspz :5hk r)gbd. 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 mad( )0 6oz wyanku.(aecde over one mile of distance by the “5-second rule” for ea() y6e(wca 0uonkzd. stimating 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 at the pain level on,tf9yij4lu6 a.-v ubf 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 sound whose in rug+dg/ + 0zit1i.qactensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound level of 95 dB when fiyb:00 jv)sbrncku l8ou- *1jj red simultaneously at a certain pv0)ckrboj10ul* ysbnj8 uj:- lace, what will be the sound level if only one is exploded? [Hint: Add intensities, not dB’s.]    dB

  A person standing a certain distance from an airplane witg:cc,gmx. r n2h four equally noisy jet engines is experiencing ag:cn2 x c,m.rg 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 saisf ;oxrk:s v*a6log( (ociqm5z )* (ged to have a signal-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 background noise for each device? 58 dB = kxfe5g qsl( r( vm*oig a)s6ocz;*:(o   $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of sound from 2;2tsbdnynt:sof) 6rtwlyj c e .hi+(i;i 8x 8a person speaking in normal conversation. Use Table 12–2. Assume the sound spreads roughly uxw+tibtnt6ir;j)d88of . hcli2 n e2y;s (sy: niformly 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 s:ny* 0 g2cyzv/ vzlkf;trikes 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 rate8vzia;z jq9- sd at 250 W, while the more modest amplifier B is rated at 40 W. (a) Estimate t-z8jviz; 9q sahe 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 130 dB when plakuxn 8kk5hza5/4mp( vced 2.8 m in front of a l(/nvxh85zkpk uma4k5 oudspeaker 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 vcl; f,rn( bz7difference in sound level of 2.0 dB. What is the ratio of the amplitudes of two sounds whose levels differ by this amount? [Hi,;lbvf r7zc (nnt: See Section 11–9.]$\approx$   

  If the amplitude of a sound wave is tripled, (a) by what f 8g(vdu./ulp pactor will the intensity increase? Increase by a factord 8/pguv pu.(l of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal displacement aggumu3kytu5wb(yh)f3. x9+ wmplitudes, but one has twice the frequency of the other. What is the ratio of theik)w .y3hu uyu5mgg3b+tf w9( xr intensities?   

  What would be the sound level (in dB) of a sound wave .uglce8s0/q3g1c:d e6h ituk in air that corresponds to a displacement amplitude of vibrating ai/lgg83 :h.dqec ecku6u1si 0tr molecules of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have what orc;nxer xewl9g8et5985 *iv sound level to seem as loud as a 100-Hz tone that has a 50-dB soundv*o c 8rxlig ;xwt5e8ee n995r level? (See Fig. 12–6.)    dB

What are the lowest and highest frequencies that an a,.w,qscc ezoj .3ow(ear can detect when the sound level is 30 dB? ( c. ,.a scjwq,e(oow3zSee Fig. 12–6.)

  Your auditory system can accommodate a huge range ofp9,kkkkt x.4enn* ajck z0;*0 mgp4d f sound levels. What is the ratio of ; .zkx kk4pkanpd4, jng0*kfe0mct*9highest 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 ubu n,c7y:rml+q 4gd .fundamental frequency of 440 Hz. The length of thend:+r c y.bq7gul,u4 m vibrating portion 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. What are ,fs r 7kw1ug2nu.ah (fthe fundamental and first three audible overtones if theu2 k(uarh fsgf.7 ,wn1 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 frm*f n 5kgc hu61(ec+udom blowing across the top of an empty soda bottle that is 18 cm deep, if you assumed it was a clefuhngckm(6 51d+* cu osed 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-tue4 o zpn,8 y1vs:mztt(be pipes spanning the range of human hearing (20 Hz t mnzepo :tzv84(,t s1yo 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 540xktz alm26 nis.;b1r2 Hz as its third harmonic. What will be its fundamental frequency if it is fing zn.sa6krl221x;ibt mered at a length of only 60% of its original length?   Hz

  An unfingered guitar s bhkcx/+j;p j05s ,nrttring is 0.73 m long and is tuned to play E above middle C (330 Hz). 5;pc jrjn0/ sk ,hbt+x
(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 o0-4gsz d/h2o utd .yjui1u+ff pen organ pipe that emits middle C (262 Hz) when the temperat4d0udth+f/ 1z . o-i fsguuj2yure 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 vf3/yw ji 9l3gqw ,0dc9g:phy20 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece of the fl rs vrs/1:u-rssqb,)sute in Example 12–10 should the hole be that must be uncovered to plr)r:/-qb rs,1usvs ssay 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 aqc u.k.oxlp7:t 264 Hz, 440 Hz, and 616 Hz, but not at any other frequencies in between. (a) Soxq .l: .cu7pkhow 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 ev-klj9 ee7h7both ends. It resonates at two successive harmonics of frequencikev-9 ej7ehl7 es 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 (wefm65 h )gko vb.z7xm1rey7$^{\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 wig .xj br .0qv-*mctn1wthin the audible range for a 2.14-m-long organ pipe atx v- gw.jc*m0r. tbqn1 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approxiv 0dh iac09f4rd 7z.b hhsq+;jmately 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. What is the relationship of your answer to the information in the graph off. h7iz a+jrbqvd 09 dchs;h04 Fig. 12–6? $f_1$ =    Hz $f_3$ =    Hz $f_5$ =    Hz

  A piano tuner hears one beat every 2.0 s when 1 tl c*k)g8hy4 ywh+pjtrying to adjust two strings, one of which is sounding 440 Hz. How far off in fret j*whk yp+8cl4g)hy1quency is the other string? ±    Hz

  What is the beat frequency if middle C (262 Hz) and 55xkgyx.q1 ao9i )cuc $C^＃$ (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 operates4d o2l: f d +lrn,t;pe.y+pcia at 23.5 kHz, while another (brand X) operates at an unknown frequency. If neither whistle canpnt+rfl. +aol;ip dc42:e, y d be heard by humans when played separately, but a shrill whine of frequency 5000 Hz occurs when they are played simultaneously, estimate the operating frequency of brand X.    kHz

  A guitar string producf 5y ,qdlvu- :sxe98rmes 4 beats/s when sounded with a 350-Hz tuning fork and 9 beats/s when sounded with a 355-Hz tuning fork. What is 89, exv-qf5dm slu:rythe vibrational frequency of the string? Explain your reasoning.    Hz

  Two violin strings are tuned to the same frequen cwu;/otz6pxak+/ 6s zcy, 294 Hz. The tension in one string is then decreased by 2.0%. What will be the beat frequency hax/ockut s;+ /pzz66w eard when the two strings are played together? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be heard if two identicalti n9ns(z ; kb6.hh-ovdg ry54 flutes each try to play middle C (262 Hz), but one is at 5.0°C and the ib(d9sov5-n; zt nhh4kg6.ry other at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks +6ena,j/t2y5emou4gk+ zvyz8h p)h g, A, B, and C. Fork B has a frequency of 441 Hz; when+hz8z5vgp 4kjea,2m)t+y/ eho 6u gny A and B are sounded together, a beat frequency of 3 Hz is heard. When B and C are sounded together, the beat frequency is 4 Hz. What are the possible frequencies of A and C? What beat frequencies are possible when A and C are sounded together?$f_A$ =    Hz or    Hz
$f_C$ =    Hz or    Hz
|$f_A$-$f_C$|    Hz or    Hz

  Two loudspeakers are 1.80 m apart. A person du6 it0u3:g *zv7xiyn 2hq g;qstands 3.00 m from one speaker and 3.50 m from the;x*tuyuig : dig0 vq3h z2q67n 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 vibratinezk8a- d: kgi,g at 132 Hz, but a piano tuner hears three beats every 2.0 s when they are pk8id:gz ae,-k layed 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, 5vxt4yawv an61norsrx-+- r.76 m in air. How many beats per second will be heard? (Assux1-ran +5x6stvo - yr va4rw,nme T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain fire engine’s siren is 1550 Hz when at rai/ xs, vwlrb7b1yf8 5est. What frequency do you det5fb/r1,abwxisl87 yv ect 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 frequencyyaziu (vtmd2 ,l/n uus6 4em02ij7p-o do you detect if a fire engine whose siren emits at 1550 Hz uly azmvsnu4i d j6/(i22oue,0-m7t p moves at a speed of 32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift in frequency if a 2000-Hz source is moving to *ag u5klt. 4iu*)+bd3rpct mqward you at 15 m/s versus you moving toward it at 15 m/s Are the two frequencies exactly the same? Are theyuualm)q k3ig*t r4p d.t*b5 c+ 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 with3,;vv yn1ypar2tpa+ u 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 y1,rnp 3;uyt2v vpa+a Hz. What is the frequency the horns emit? Assume T = 20 $^{\circ} $C    Hz

  A bat at rest sends out ultrasonic sound waves at 0ifd(oit5s55 7 spvd c50.0 kHz and receives them returned from an o cdvifi(ops 5 705ts5dbject moving directly away from it at 25 m/s What is the received sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed of 5 m/s As it flies, the bof* ywor0. x0kat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency does the bat hear inw.f o0xrkoy0* the reflected wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experiments, a tuba was played onl*62 w2gte .luflff,v a moving flat train car at a frequency of 75 Hz, and a second identical tuba played the same tone while at rest in tht.v uel2,f 6llf2fw* ge railway station. What beat frequency was heard if the train car approached the station at a speed of 10 m/s ?   Hz

  A Doppler flow meter uses ultrasound waves to measure blood-flow speeds. Suppossiafug3qj1( 1 e the (qf3isg 1u1 jadevice emits sound at 3.5 MHz, and the speed of sound in human tissue is taken to be 1540 m/s What is the expected beat frequency if blood is flowing in large leg arteries at 2 cm/s directly away from the sound source?   Hz

  The Doppler effect using ultrasonickug7 g) 44yrde 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* w1u/ty z zsjpn*8b;d of frequency 570 Hz. When the wind velocity is 12 m/s from the nortj8 zy s1wz;ud /bp**nth, 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 object movi;m uvj;ozppcr6 o:sln ;h3. *fc:a5sing 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 2.3e0pvqd yodoe7 ft(fi+7* +o2h where the speed of sound is 310 m/s (a) What is the angle the shocp qv++oi e*df7t07 (yooe d2fhk 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 at(4f0b4w4g h-9cs+ws gj7)rrou /u n pt whgfi6mosphere of a planet where the speed of sound is only a4fnc pj sugwgb+9u ) hrs(ow fi4w-7hgt 0r64/bout 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.i7 r .dbd/p/xj Determine the shock wave angle itr7 /d/ij d.bxp 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 pjaiu d)klp 2:tt*fi8n(aj,fudo(95$/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly overhead and see a plane exactly 1 qzxr/,j g 75mj/jrpb6 9bygt1.5 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. See Figx1,pq/59 m zgjj7rb yrgtjb6/. 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 sonaoz/o+k n das1k;qv: 0lr device that sends 20,000-Hz sound pulses downward from the bottom of the boat, and then detelk0+zod:a ; sq1ov/nkcts 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 octfl,1v j3vuy 2mgi( *rhaves are there in the human audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display called a sewer pipe symphony. It consists osv6 5ve;bb; tr:o3h4 t bleqk/f many plastic pipes of various lengths, which are open on both endsel6:s rbtvhe;3kv/ ;4b5qtb o.
(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 ,n5g- ccou(rt close to the threshold of human hearing (0 dB). What will be the sound level of 1000 such mosquicg(nt-,c r5uo toes?    dB

  What is the resultant sound level when an 82-dB sound and an 87-dB sound ah-cf b7jic v zr0w)82kre heard simuljv07wb8 2)z fccki-hrtaneously?    dB

  The sound level 12.0 m from a loudspeaker, placed in thxwpu.r:yg8(t7 )a i lse open, is 105 dB. What is the acoustic power output (W) of the speaker, assuming it y:)gx pla.r7 usitw(8 radiates equally in all directions?    W

  A stereo amplifier is rated at 150 W ou 5kpwin eq+.n;n*v ;sktput at 1000 Hz. The power output drops by 10 dB at 1sn+p*ki;nknv eq;. w 55 kHz. What is the power output in watts at 15 kHz?    dB

  Workers around jet airpqp: up 7h:,unuxkc w +l54/cjcraft 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 intercepted by an unprotected ear ank4u,: jupwpcu p7x:qc /h5l+t a distance of 30 m from a jet airplane engine?    W

  In audio and communicationse gp5 .akw66rn0qhe d3l9k uj7 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 violifrjp(,;jnt i/f3 qh.tur7b*d n is tuned to a frequency 1$\frac{1}{2}$ times that of its neighbor. The four equal-length strings are to be placed under the same tension; what must be the mass per unit length of each string relative to that of the lowest string?
$f_{A}$ =    $\mu_{A}$
$f_{B}$ =    $\mu_{A}$
$f_{C}$ =    $\mu_{A}$

  The A string of a violin is 32 c(( p1daen.w63u me clcm long between fixed points with a fundamental frequency of 440 Hz . ecacp3lw1d6(e ( unmand 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 abo f.hlbitlr78g4 5)ox xve 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.o7 lx5gt8i )lxrhbf 4 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 nejg:kmz;/ru-3wk rp7d wwil0 9ayul 28ar a tube that is open at one end and also 75 cm long. How much tension should be in the string if it is to produce rjgwrip w/0yka2lrd mk8w:u79 lz3-u;esonance (in its fundamental mode) with the third harmonic in the tube?    $ \times10^{ 2}$ N

A highway overpass was observed to resonate as one yzy4 5yonh ;*kfull 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 50 nvpsb+5ukxp9.4wbf7 0–1000-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 person moves about and finds that the sound level is minimal at a point 0.34 m 9v.bwk psu7x f5+ pn4bfarther from one source than the other. What is the frequency of the sound?   Hz

  Two trains emit 424-Hz whistles. One zh0nkz. .3mpbmh.6aztrain is stationary. The conductor on the stationary trai3k.hhm.zb.mna 06pz zn hears a 3.0-Hz beat frequency when the other train approaches. What is the speed of the moving train?   m/s

  The frequency of a steam train whistle a8 23vtfxpy1ols it approaches you is 538 Hz. After it passes you, its frequency is t1oy 2p3vx8lf measured as 486 Hz. How fast was the train moving (assume constant velocity)?    m/s

  At a race track, you can estimate the speed of cars just by le8u nw e5+i2gfistening to the difference in pitch of the engine noise between approaching and receding cars. Suppose the sound of a f2+inuwg 58eecertain 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 togethj.vemw aadk3 s9.pv+(er, produce a beat frequency of 11 Hz. The shorter one is 2.40 m long. a9s .3djv kae pwmv(+.How long is the other?    m

Two loudspeakers are at opposite ends of a railroa( - dthf,:x1kuq nsvn(d 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 A, infkt:(dvs x,(nuh1n-q front of the car, (b) he is between the speakers, at B, and (c) he hears the speakers after they have passed him, at C?

  If the velocity of blood flow in the aorta is normally about 0.32 m/ox8 u4v vpo/c1s what beat frequency 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 scpx8o1v4/vu o peed of $1.54 \times10^{3 }$ m/s   $ \times10^{3 }$Hz

  A bat flies toward a moth at speed 6.5 m/s while the mot (-ncmwbvn y7,+ybnwm,d ( 5ulh is flying toward the bat at speed 5 m/s The bat emits a sound wave ofym5 vc+duwwbm-(n(, 7,ylnbn 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 high frequency sound pulses as it approacr /515 l(fphuhujgp iq,xz-9mhes a moth. The pulsesrjxpz(5f5, pmuhgi- ul9qh/1 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?    m

The “alpenhorn” (Fig. 12–38) was once used to ra2).+,c tjysek u 9drab,*fhsend 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 overtonesc*t+a2,b.fry rsa uk,)edjh9 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 s3a l pd.n 95sgsk4 3cez.+smmof standing waves, which can cause acoustic “dead spots” atp93 a34knm..esz s m+ldcs5g s 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 demonstrati,gvy2 c2w 3c7kw2 xojza:.d gcon, called “singing rods,” involves a long, slender aluminum rod held in the hand near the rod’s midpoint. The rod is stroked with the other hand. With a little practice, the rod can be made to “sing,” or emit a j ccwg2 yv3kzd,:a2wo7gx2c. 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 fgzz46x4 t7 .josua ww2requency of about 1000 Hz is 2a.j4xs4wo7z zg 6tu w$I_0$ = $1 \times10^{12 } W / m^2$ 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 atao e0kp m-tw ;4xh ;gvat9;g*b Mach 2.0. An observer on the ground hears the sonic boom 1.5 min after the plane pasve g9tw* maobahg40k ;-;;p txses directly overhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboat is 15.sy zi. 3mre.0hixuqp b 2.vq:/wf, zy $^{\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