What is the evidence that sound travels d7m ,yw mved:fm;51 dmas a wave?

What is the evidence thxujz(gx3i7sm )t7-08lei miv at sound is a form of energy?

Children sometimes play with a homemade “telephone” by atblz:bh-:1dsn g r 18gttaching 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). Exp:g:lb r dgn1 81shbtz-lain clearly how the sound wave travels from one cup to the other.

When a sound wave passes from air into water, do you expect the frequency or;rh,f6 s;1sb o-rw keo wavelek,e osr;r;os6fw1hb - ngth to change?

What evidence can you give that the speed of sound in air does not depend sil)lww-vih v 78ok.f*mgnificantly on freq vk-)v*7l.w mfwo8 hliuency?

The voice of a person who has inhaled helium sounds very up*e,gb -;gb qrk/ 4dr*mi; 2 vywzdc7high-pitched. Why?

How will the air temperature in a room affe:(h)r c ugvf94sic /fvct the pitch of organ pipes?

Explain how a tube mig4iy.91iz har2n qze;j zpmg 38ht be used as a filter to reduce the amplitude of sounds in various frequency ranges.qphznz2r jia 41893i zeymg .; (An example is a car muffler.)

Why are the frets on a guitar (Fig. 12–30) s u*foi 0 8 y;g1hbev:ay j2dqo*.p.yoepaced closer together as you move up the fingerboar81ibo.of:ovq eug;ye .* * ja0ypdh 2yd toward the bridge?

A noisy truck approaches you from behind a building. Initially you hear it /nbs7 6wulv5+kg8 y5mkum3 qdbut 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 Section 11–15 on diffracq85skn bu6lgyv53/7+dmu kw mtion.]

Standing waves can be said to be duedp(pu y) b7;kin*4tbld65jor to “interference in space,” whereas beats can be said to be 7nbd 4*u(ipyjk;)dl pt6r5 obdue to “interference in time.” Explain.

In Fig. 12–16, if the frequency of the speakers were lowered, s:i+yn+ va5czdw /8namm 3tf- would the points Dd: mytnazn+8 wfa+mv/si3c5 - and C (where destructive and constructive interference occur) move farther apart or closer together?

Traditional methods of protecting784b*gh8rmszc 1w8njvvezkr. xk 6crj10o i; 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 headphonejo xr v1r*81s8e.47wgk8k i6;cvz h n0j bmczrs 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. Each wave can be thoub4xqu pa7 v+c;ght of as a superposition of two sound waves with slightly different frequencies, as in Fig. 12–18. pv 7cax+uq;b4In 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 and observer move in the same dimvt3y q/ 1o*hvsp3+rg k(gy.f rection, withq/3m .3k g hp *(1ygfry+votsv the same velocity? Explain.

If a wind is blowing, will this alter the vha.jt*wkd 3bq*vl/.c w 7*vvfrequency of the sound heard by a person at rest with respebl*vk. q j3aw*c/.tv vv*wd7hct to the source? Is the wavelength or velocity changed?

Figure 12–32 shows various positions of a child in motion on a swing. A monito;f. fxstb.6 ror 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 sound o;6ot..fbr x sff the whistle? Explain your reasoning.

  A hiker determines the length of a lake by listening for the echo on* ,v/ xbpyk.cst; 3oif her shout ref .pso/kn;c 3*,vitx yblected by a cliff at the far end of the lake. She hears the echo 2.0 s after shouting. Estimate the length of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side dj*d9 t);5onci pcmrx /+shz*ldh-a7of his ship just below the waterline. He hears the echo of the sound reflected from the ocean floor directly below 2.5 s later. How deep is the oceor5htpz9nj+-*)s lcxh dc;dmd /i *a 7an 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 icb/jm sk de6/xk*8d(n n air at 20 $^{\circ} $ C for sounds in the maximum range of human hearing, 20 Hz to 20,000 Hz. $\lambda_{20Hz}$ =    m $\lambda_{20kHz}$ =    $ \times10^{-2 }$ m(b) What is the wavelength of a 10-MHz ultrasonic wave?    $ \times10^{ -5}$m

  An ocean fishing boat is drifting just above a school of tuna fcd2+8bv(ve emrzqs*8ta n- -)-ogfvon a foggy day. Without warning, an engine backfire occurs on another boat 1.0 km away (Fig. 12–33). How much time dotzmvbsfge n(a-+vf ceq82*vr-8-) 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 ma)9onm3ap gux :kes when striking the water below is heard 3.5 s later. How high i g9:nmuop x)3as the cliff?    m

  A person, with his ear to the ground, sees a huge stone strike the concr 6)xfn +d)ymn+ejtfn/ ete pavement. A moment later two sounds are heard from the impact: one travels inn /) mn)f+dfy 6extj+n the air and the other in the concrete, and they are 1.1 s apart. How far away did the impact occur? See Table 12–1.$\approx$    $ \times10^{2 }$m

  Calculate the percent error made over one mile of distance by the “5-secp0twxg u .(; f,kwhgs)ond rule” for estimating the distanu f).0ktwp s( ,xh;gwgce 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 zm1 mblatm07ym u1 i3,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 sound whose intensity is ul5yw(dk,, d u$2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produ/;om zrq/ xqr:ce a sound level of 95 dB when fired simultaneously at a certain place, wzq//q :;rmo xrhat 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 with four equally noisy jh n3j e,ubo +sbtwuo 6-eil521et 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 intensities, no u1 e,el-56u2 3woitso jhbbn+t dB’s.]    dB

  A cassette player is said to have a signal-to-noise ratio of 58 dB, whereaq4)3:kuz boumn pts)uma.g n+3byf: .s for a CD player it is 95 dB. What is th3 )uu p )fz bn::3sma.n4oku yqbgm.t+e ratio of intensities of the signal and the background noise for each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of sound from a person speakingne:k 7 8ihcq/n in normal conversation. Use Table 12–2. Assume the sound spreads roughly uniformly over a sphe7/eq :i nkhc8nre 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,+pq xlv*q4nq+rb8-l h zdg9qtrikes 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 m ilt 9,sox)hb4kmd6) A is rated at 250 W, while the more modest amplifier B is rated at 40 W. (a) Estimate the sound level in decibels you would expect at k9ix)mlsbd)m ,6h4 toa 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 pla) pwuww /p 7ndj35f6v1d/puwbced 2.8 m in front of a low76//nd w w1ufuwv5b 3pp )djpudspeaker on the stage.
(a) What was the power output of the speaker, assuming uniform spherical spreading of the sound and neglecting absorption in the air?$\approx$    $ \times10^{2 }$W(“Round to one decimal place)
(b) How far away would the sound level be a somewhat reasonable 90 dB?   $ \times10^{2}$m

  Human beings can typically detect a difference in sound l(emj szq1p*)jevel of 2.0 dB. What is the ratio of the amplitudes of two sounds whose*es 1j)jzqm p( levels differ by this amount? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound wav 5)pim1iw i syjl+z9mw7rhj3,e is tripled, (a) by what factor will the intensiim1 lpi+5yw7 rj3s )zji,9mwhty increase? Increase by a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal disp9 sx rcyn)d;b.z: 8kdhlacement amplitudes, but one has twice the frequency of the other. ;z8.nd)d rs9ckyhb x:What is the ratio of their intensities?   

  What would be the sound level 24vhospx 3sj2 (in dB) of a sound wave in air that corresponds to a displacement amplitude of vibrating air molecul4sv pxo2sh 32jes of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level to seem as loud as a 10dq0c:n jupd):t*dhuf f37p 4g0-Hz tone that has a 50-dB sound level? (See Fig. 12–6u)u *t0p:jq7g4 dncphf f:d d3.)    dB

What are the lowest and highest frequencies that an ear can detect when thon6 4se-hw5yz9rsz qbl u/s1+ e sound level is 30 dB? (See F /4h5 ssn6 9-zsqlbe1+zyrwuoig. 12–6.)

  Your auditory system can accom+fe a/w7rhc1s modate a huge range of sound levels. What is the ratio of highest to lowest inte7+/h1car f eswnsity 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 fundamenj7ed0 4 8;lqg4zjl;:su bc rfotal frequency of 440 Hz. The length of the vibrating portifjcs07l4;8bq: r uojz e4; dglon 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 ot ur0g9 i8a)eqg*p/, yebl* rare the fundamental and first three audible overtones if the pip r)eibg8la,* /t09o e qrg*yupe 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 +8 7hujgeljx -expect from blowing across the top of an empty soda bottle tha-gj7ueh j +lx8t is 18 cm deep, if you assumed it was a closed tube?    Hz (b) How would that change if it was one-third full of soda?   Hz

  If you were to build a pipe organ with open-tube pipes spanning the ran): ( vtcw:iekf49k umv18ueumge of human hearing (20 H(8mtvcemu i4:f:9u ) kuwv1e kz to 20 kHz), what would be the range of the lengths of pipes required? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

  A tight guitar string has a frequency of 540 Hz as its third harmonic. What wilkhlr.2+kvo+ x l be its fundamental frequency if it is fingered at a length of only 60% of r+kkxv2lo. h +its original length?   Hz

  An unfingered guitar string is 0.73;z3kgtwe 9a*l m long and is tuned to play E above middle C (330 Hz)9k e; gtz3l*wa.
(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 pipe5ov tu2x,n;fuzc h( i7 that emits middle C (262 Hz) when the temperature is h ot2,i7xc;u(fn5zuv 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 20nxdt *xc/+j lt*k4,dn $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece of the flute in Example 12–10 should the hole be ,boiafip-lc5 ,z y 1f fae0q+,that must be uncoverf 5iq0-of i+ yf,cb pzae,1,laed 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, andjgk xp3gk q0e4s2kn+h)l - l0d 616 Hz, but not at any other frequeng0 n)khl+g-l2k pjeq30k s4xdcies in between. (a) Show why this is an open or a closed pipe. ----待选择----closedopen  (b) What is the fundamental frequency of this pipe?   Hz

  A uniform narrow tube 1.80 m long is open at both ends. It resonates at two s ffujn ox4: 3v wo04rwa;z0tb2uccessive harmonics of frequencies 275 Hwxr4o;b2 jav:t0fzf on 04u w3z 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 zdl*dz35hgjej 3k3cu .h( ds/wi p-7p$^{\circ} $ C is to be designed to produce two successive harmonics at 240 Hz and 280 Hz. How long must the pipe be, and is it open or closed?  ----待选择----closedopen  f =    m

  How many overtones are present within the 0 j426)quqheryxrd +saudible range for a 2.14-m-long organ pipe at 20 rj)yu6x+2 4hr 0sedqq$^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is appro9ao snc /qp+.frmx7 7yq .dddcbw3b76ximately 2.5 cm long. It is open to the outside and is closed atx f 6.7cb39 p7ns q7ocyq./dd bwrm+ad 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 of Fig. 12–6? $f_1$ =    Hz $f_3$ =    Hz $f_5$ =    Hz

  A piano tuner hears one beat every 2.0 s when trying to adjust two strings, onetcjz ;, nc(+fb of which is sounding 440 Hz. How far off j(z tcb f;c+,nin frequency is the other string? ±    Hz

  What is the beat frequency if middle C (262 Hz)r *d,5tkbsuyc 6/;awk 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 (t-jq*nb va,p+ brand X) operates at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whine of frequency 5000 Hz occurs when they are played simultaneously, estimate the opet,vq-* pj a+bnrating frequency of brand X.    kHz

  A guitar string produces 4 beats/s when sounded with a 350-Hz tuning fork1n0*fs6t hz)sjd(yt b and 9 beats/s when sounded wit)s(fsztdj 06nbh 1y*th a 355-Hz tuning fork. What is the vibrational frequency of the string? Explain your reasoning.    Hz

  Two violin strings are tuned to the same frequency, 294 Hz. The ten 0 ;wpn;l4(i vcbtsv)**dci0tlif8xxsion in one string is then decreased by 2.0%. What will be the beat frequency heard when the two lf*vsic ;txi0tlbvp(w)*8di0; cxn 4 strings are played together? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be heard if two identical flutes ea. (r,biij40e,yxipw v ch try to play middle C (262 Hz), but one is at 5.0°C and the oy,rixiivwe .bpj4,(0 ther at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks, A, B, and C. Fork b mij,gxp6, i6*jx ,hhlj7uh1B has a frequency of 441 Hz; when A and B are sounded t1m hgjx,hji* jpi6 hbx 7l,,6uogether, 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 stands 3.00 m from one speaki *y r+z/1(apqasd5uj er and 3.50 m from the ora s*j i+ 5ypz1adq(u/ther.
(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 k1nkm1dr*9j+qov( aoojnb75 be vibrating at 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 must be the frequency o7 v( 1a*krj9bo5n +jkqmoodn 1f the other ?   Hz    Hz
(b) By how much (in percent) must the tension be increased or decreased to bring them in tune?   % increase    %decrease

  A source emits sound of wavelengths 2.64 m and 2.76 m ini.d5nn7hj9yuur7ab k;b/3d c air. How many beats per5/9id cr7dn.nabhuk 7 buj3;y second will be heard? (Assume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain fies ignv1c x.5l) vg/,wre engine’s siren is 1550 Hz when at rest. What frequency do you detect if you move with a speed of 30 m/s )vls ggixwcn5v e/ ,.1
(a) toward the fire engine,    Hz
(b) away from it?   Hz

  You are standing still. What frequency do you detect if a fire enfw*pnx( :wc -ny q:ep1gine whose siren emits at 1550 Hz moves at a speed of(c-fx yqn: e*p1w:p nw 32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift in frequency )b2z; naj hg4wif a 2000-Hz source is moving toward you at 15 m/s versus you moving toward it at 15 m/s Are the two frequencies 4g2hj)w; ba nzexactly the same? Are they close? $f'_{source\,movine}$    Hz
$f'_{observe\,movine}$    Hz
(b) Repeat the calculation for 150 m/s and then again
$f'_{source\,movine}$    $ \times10^{ 3}$Hz
$f'_{observer\,movine}$    $ \times10^{ 3}$Hz
(c) for 300 m/s What can you conclude about the asymmetry of the Doppler formulas?$f'_{source\,movine}$    $ \times10^{ 3}$Hz
$f'_{observer\,movine}$    $ \times10^{ 3}$Hz

  Two automobiles are equipped with the same single frequency horn. When one is a 5vmm-oh/v- tzt rest and the other is moving toward the first at 15 m/s the driver at rest he-/zhm5v -v tmoars a beat frequency of 5.5 Hz. What is the frequency the horns emit? Assume T = 20 $^{\circ} $C    Hz

  A bat at rest sends out ultrasonic sound waves at 50.0 k+zp :y ny qsqp7-/(sswHz and receives them returned from an object moving directly away from it at 25 m/s What is(syz 7syqp- /psnqw+: the received sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a pr7y/c 0w ytmcd )h980m9cj /genp j.cspeed of 5 m/s As it flies, the bat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency does the bat hear in the reflecte0nm8d cejw7.yp g9cj0rhm )p9 c//tc yd wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experiments, a tuba was playedvc)wn+8*zh w r 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 be )vw*h +c8zwnrat frequency was heard if the train car approached the station at a speed of 10 m/s ?   Hz

  A Doppler flow meter uses ultrasound w(eulc bo;yf ccj5b7et: x ; )i0.b5ynpaves 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 directly away frcy bp cun;y.5 7i: tb 5ex(becf;)lo0jom the sound source?   Hz

  The Doppler effect usingnw.d2 v4 aa71cjaymn l )xe**t ultrasonic 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 0ovm:g qnk ti/:dk5q.Hz. When the wind velocity is 12 m/s from the north, what frequency will observers.:kkgo5n ti:d0m q/ qv 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 moving on land if its speed *; tx sm6ovld8at 20 $^{\circ} $C is Mach 0.33?    m/s
(b) A high-flying jet cruising at 3000 km/h displays a Mach number of 3.2 on a screen. What is the speed of sound at that altitude?    m/s

  An airplane travels at Mach 2.3 where the speed of sound is 310 m/s (a) What isimgm( l5 a(hh8 the angle the shock wave makeshla5h ( (im8mg 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 the speed of 0dy-fq q;i;cb v)l:rr: kru1hfiw5(u sound is only about : c-uq bif ;v:irkydrw );ru10fq 5lh(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 850;zcig ; dj//uquh0nt ;0 m/s strikes the ocean. Determine the shock wave angle q;t/cui hz0ngjd;;u/it 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 y8-xrbwumgq q(2 0d(lf2 ) b6zw,wfab$/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly ov6alzf5 cop11r erhead 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. See Fig. 11p o6azrclf1 52–34. Determine
(a) the angle of the shock cone, $\theta$    $^{\circ} $
(b) the speed of the plane (the Mach number). Assume the speed of sound is 330 m/s   

  A fish finder uses a sonar device that sends 2(ngv-eu f7a e30,000-Hz sound pulses downward from the bottom of the boat, and then detects echoes. If the maximum depth for which it is designed to work is 200 m, what is the minimum time between nv e(u-7af3gepulses (in fresh water)?    s

  Approximately how many octaves are there in the humd :eyg9x7/g-wfy *ct5o-gpj 4 csmi c/an audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display called a sewer pipe symphony. It consi u9 oif6+yzx ta5i/ w8uo47yodsts of many plastic7u o+uziyoxi6y 8/ twa9o45f d 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 .s+(v3u m;nptv nvc2i person makes a sound close to the threshold of human hearing (0 dB). What will be the sound level of 1000 such mosquitoes?n2. n(tspvc;3imv+vu    dB

  What is the resultant sound level when an 82-dB sound adr7s* m w4nvv*nd an 87-dB sound are heard simultaneously? 7nvwd4v s*mr*   dB

  The sound level 12.0 m from a loudspeaker, placed in the open,73dxr--w7cm d hjfuw t4ydo5z a2d4 01uabrd) is 105 dB. What is the acoustic power output (W) of the speaker, assuming it radiates eq rz2d7ot -b)705w w3mu4d ahrayx f-cjd4du1dually in all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 ve/mvmf;g+;s ;kji h8Hz. The power output drops by 10 dB at 15 kHz. What is t8sefi; mvgv; ;mh+ jk/he power output in watts at 15 kHz?    dB

  Workers around jet aircjg h zw9qagxg . w3m. vq4zo8goe8e-9/raft 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 at a distance of 30 m xqmz8.gzhe qgw ggje.4a93 wv8-o 9 /ofrom a jet airplane engine?    W

  In audio and communications systems, the gain,ye0f6 25n5 po.ep8ojhbxn j3p $\beta$ 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 tomo+j+ df7d6p v 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 viol8y+c7ail cn 5xix z+8vin is 32 cm long between fixed points with a fundamental frequency of 440 Hz and a mass per unit le+v5i7yx 8zln icx+ca8ngth 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 vibratio9m2a dirgz zyu 462ue*n 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 tzrdgay9ze2*u6 u2i4m o 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 strinu7nr99qgog)t*9q q9gqxo1eg g of mass 2.10 g is near a tube that is open at one end and also 75 cm long. How much tension should be in the string iog x9g9tgr91qu)qqong q7*9 e f 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 resonat(, xi0lu +kfs 0ydx/eue 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 r ;kqns; 3:;q7xv5f /rymvadptone in the 500–1000-Hz range coming from two sources. The sound is loudest at points equidistant from the two sds vrxrf p5/m3a;n7; ;q:kvqy ources. To determine exactly what the frequency is, the person moves about and finds that the sound level is minimal at a point 0.34 m farther from one source than the other. What is the frequency of the sound?   Hz

  Two trains emit 424-Hz whistles. One train is stationaryf hai3mq 2) ,rpijpm7omc,q(( ,gzg17xkk qw(. The conductor on the stationary train hears a 3.0-Hz beat frequency when the other train approaches. What is the speed o kkiomq7a(qmm17wg,x2zq fhjgp(ri), p,3 c(f the moving train?   m/s

  The frequency of a steam train whisr)9 b7lkmnrcl5 v e tma0h24z0tle as it approaches you is 538 Hz. After it passes you, its frequency is measured as 486 Hz. How fast was the train m0 5remn74c9 lblv a2kt0h mz)roving (assume constant velocity)?    m/s

  At a race track, you can estimate the speed of f.pei, rgyd3u;d gj-) cars just by listening to the difference in pitch of the engine noise between apid-;e yd.) g3r,fg jpuproaching 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 frequencytes-r) da b07/)yjnov of 11 Hz. The shorter one is 2.40 m long. How long is the ovo snr ejb)d/-)y 0at7ther?    m

Two loudspeakers are at opposite ends of a railroad car as i9s,yfyg q5b8 i:8:vhfdj k4b .1lt xqpt 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, in front of the car, (b) he is between the speakers, at B, and (k,:byyfbj48l i 9dhf: q.18tgvq xsp5c) he hears the speakers after they have passed him, at C?

  If the velocity of blood flow in the aorta is normally about v*y9hkgv.;o m0.32 m/s what beat frequency would you expect if 5.50-MHz ultrasound waves were directed along the flookvv*9.; mg yhw and reflected from the red blood cells? Assume that the waves travel with a speed of $1.54 \times10^{3 }$ m/s   $ \times10^{3 }$Hz

  A bat flies toward a moth at speed 6.5 m/s while5v9tp nd,q y)r the moth is flying toward the bat at speed 5 m/s The bat emits a sound wave of 51.35 kHz. What is the frequencyyd9q5pv ,rt)n of the wave detected by the bat after that wave reflects off the moth?    kHz

  A bat emits a series of high frequency sound pulser+6jwlun mdai6m /-p 1wdr q7+s as it approaches a moth. The pulses are approximately 70.0 ms apart, and em wnd u-1+pr+d76i mjlaq/w 6rach 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 send signals )dm4reuj-9o ofrom 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 on jr4uem-ood9) ly 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 slpse;t5p5ag d5w zta)+5gk mbn. i9c+tereo listening can be compromised by the presence of standing waves, which can g.e5sdbiz+5t );9pam+kt n5wlagc 5 pcause 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 rods,” be1ur) 13ah4.benaro involves a long, slender aluminum rod held in the hand near the rod’s uben oar1r1 a3e b)h.4midpoint. 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 thre k3z*sd1 bvw am,6.szt6b zn+eshold of hearing for the human ear at a frequency of about nv z+*k3. bm6zdzwebat6s ,s11000 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 the son geg;(ia tp/,hic boom 1.5 mgtie/gp (,;ah in after the plane passes directly overhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboat6m,8hnowvn2 x 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