What is the evidence that *dycw- oq/nw9-2wmno sound travels as a wave?

What is the evidence that sound i( au1dt(hhz)e n/d83b zg+czfs a form of energy?

Children sometimes play with a ho6dv ut1wmz-g- kf9 1eomemade “telephone” 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 td9mgo-6wzvf1 -ke 1 uone cup to the other.

When a sound wave passes from air into wathbs)x*eg8 p 5c. sdj6per, do you expect the frequency or wavelength to c8j xh)d*c 5ppessg .b6hange?

What evidence can you give that the speed of sound in air does not depend sisg 4uot7)gm 7agnificantly gm7)4 su7oagton frequency?

The voice of a person who has inhait nc8.*ja :n4ls7 m1odtj5u aled helium sounds very high-pitched. Why?

How will the air temperature in a re3hw fne7 hn:1so3gq(oom affect the pitch of organ pipes?

Explain how a tube mighcussj1 -bb,p p.t7tk8cp2oa 1air0 1 it be used as a filter to reduce the amplitude of sounds in various frequencu 1aat87.-i121t ,kpcsor0ppbsicb jy ranges. (An example is a car muffler.)

Why are the frets on a guitar 6.k6ipd2 g ask) l7fpw(Fig. 12–30) spaced closer together as you move up the fingerboardw62gk.spdp7)kf ia l 6 toward the bridge?

A noisy truck approaches you from behind a building. Initially you hear it but cyi4 y(zfoet.7 annot see it. When it emerges and you do see it, its sound is suddenly “brighter” — you hear fe4o. yty7 z(imore of the high-frequency noise. Explain. [Hint: See Section 11–15 on diffraction.]

Standing waves can be said to be due to “inte34n( 3lzs d*ii(xmwhrrference in space,” whereas beats can be said to be rdi 43mz x(s(nhi*lw 3due to “interference in time.” Explain.

In Fig. 12–16, if th wu56ne1z/q-jy w5taaa. jso4 /-udfn e frequency of the speakers were lowered, would the points D and C (where destructive and constructive interference occur) move farther apart oro1uw-/ze5 ua 4.5afnns-w djj t6y q/a closer together?

Traditional methods of protecting the hearing of.csn1 hx firf 3//5kvq 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 itfvc3 1r/h iqksn5 x/.f 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. Each wave can be thought of as a su* joqk+4/ezbltc ,6 nqperposition of two sound waves with sli4,zjkqctn+b*/ 6e ol qghtly 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 sh)/u)jjf*gkp( qsvj) pc55o vs); fouvift if the source and observer move in the same direction, with the same velocity)5f(j;ssg v5 uo) )po)cfukqvp jv/j*? Explain.

If a wind is blowing, will this alter the frequency of qf9*(5n);ftujkj nx( g)mfpathe sound heard by a person at rest with respect to the source? Is the wafgpn (k j)(j5fa tm;*xuf)9qnvelength or velocity changed?

Figure 12–32 shows varb 0)z,v x2ur:czz2uto a. e+daious positions of a child in motion on a swing. A monitor is blowing a whistle in front of the child on the ground. At which position, A through E, will the e:xdu,b+.zz r)c022touz vaachild hear the highest frequency for the sound of the whistle? Explain your reasoning.

  A hiker determines the length of a lake by +i)3m,9oosdyex ux 4z bgwv96 p6ejs(listening for the echo of her shout reflected by a cliff at the faj4 web p6,ox+)xgsuey 39v zsim(6 9dor 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 k1u fcyi n.84 8t8lils7uu-ccof his ship just below the waterline. He hears the echo of the sound reflected from the ocek- uc84n c.ti8l y1i8fluscu7an floor directly below 2.5 s later. How deep is the ocean at this point? Assume the speed of sound in seawater is 1560 m/s (Table 12–1) and does not vary significantly with depth.    $ \times10^{ 3}$m

  (a) Calculate the wavelen+ill v:8mf2c5qy7v1 q toc ;nggths 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 of tuna t4 uvd 6va2dw(h.fs is nr5/:bon a foggy day. Without warning, an engine backfire occurs on another boat 1.0 km away (Fig. 12–33). How much time elapses before the backfire is heard (a) by the t.v sndw asr 2v6h:df(u54i/bfish,    s (b) by the fishermen?    s

  A stone is dropped from the top of a cliff.(2ot -/maxdmx The splash it makes when striking the water below is (2 o-mdxt x/maheard 3.5 s later. How high is the cliff?    m

  A person, with his ear to the grid 0r-;2m aw gq3 +3mo4znogfround, sees a 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 they are 1.1 s apart. How far away did the impact occur? See Table rd nzoqr3;wfi-42gmo3 a m0+g12–1.$\approx$    $ \times10^{2 }$m

  Calculate the percent error made over one mile of distance by the “5-second o0 o +zg5z9po nnzp4w0rule” for estimating the distance from5n nzwo00zp4ogp+ z9o a lightning strike if the temperature is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity of a sound :o ilhzo-sv,2 at the pain level of 120 dB?    W/$m^2$Compare it to that of a whisper at 20 dB.    $ \times10^{-10 }$W/$m^2$

  What is the sound level of a sound whose intens,iihd:.sq g rhwpu212 ity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound level of 95 dB when fired simult- tscle p,(iou)n 2 j.z6c-n)fze,ypc aneously at a certain place, what will be the sound level if onlz6celpf) u sct,oiz.npc--j)y 2(,e ny one is exploded? [Hint: Add intensities, not dB’s.]    dB

  A person standing a certain distance from an airplane with four equally noil 3)uvx ,g tx(3ho0karsy jet engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person experience if the captain shut down all but one enra,h0kxvo()ux3 gl 3 tgine? [Hint: Add intensities, not dB’s.]    dB

  A cassette player is said to have a signal-to-non eif2rdlp4/ -ise ratio of 58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensities of the signal andnfd4pil -/e2r the background noise for each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of sound from a person speaking (-emr,kie -nfin normal conversation. Use Table fe(n ,kr--ei m12–2. 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 strikes an eardrum whosehv ro mivkp/pow +x8 g+k;e4+qq6*ly( 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 modesto4o c:0vct8u+,ojy v la7wo9 i amplifier B is rated at 40 W. (a) Estimate the sound level in decibels you would expect at a point,autol9oc7+ w 4: ojo vi0vy8c 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 registered1wte67rkh-zf 130 dB when placed 2.8 m in front of a lz f1re wkt-7h6oudspeaker on the stage.
(a) What was the power output of the speaker, assuming uniform spherical spreading of the sound and neglecting absorption in the air?$\approx$    $ \times10^{2 }$W(“Round to one decimal place)
(b) How far away would the sound level be a somewhat reasonable 90 dB?   $ \times10^{2}$m

  Human beings can typically detect a difference in sound level of17f1qrgwcw c f d avqg01a3k./ 2.0 dB. What is the ratio of the amplitudes of two sounds whose levels diffq 7gw1ra1w.f /1 dfqvg ka03ccer by this amount? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound waz9i; d ccqb -swdpv3g0i3c j6: csel.(ve is tripled, (a) by what factor will the intensity incread ijecc6 dil9bs0;(cp3zgvs qc3- .: wse? Increase by a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal klt88 3e/ oqqfdisplacement amplitudes, but one has twice the frequency of the other. What ot3lkf8q / q8eis the ratio of their intensities?   

  What would be the sound level (in dB) of a sound wave in air l+43yx izhqr3that corresponds to a i3 + lq4hrz3xydisplacement amplitude of vibrating air molecules of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level to s,23ik6hjgabc i ridlr9 :;y1xeem as loud as a 100-Hz tone that has1rgjalr62dycx;,93iib: ik h a 50-dB sound level? (See Fig. 12–6.)    dB

What are the lowest and highes,y*ps2 dcoc :tt frequencies that an ear can detect when the sound level is 30 dB? t2 c p*cyo,:ds(See Fig. 12–6.)

  Your auditory system can accommodate a huge range of sound levels. Whadq4 *yr /(l;rpbxqg6ft is the ratio of highest to ;q* r6bqrx l/p (4ygfdlowest 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-gqur. d-/m bvequency of 440 Hz. The length of the vibratingur mqbdg--/v . 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 the fundamental and first p., v0eqz gro.three audible overtones if the pipe ivog.e0z,qp r .s
(a) closed at one end, $f_{1}$ =    Hz $f_{3}$ =    Hz $f_{5}$ =    Hz $f_{7}$ =    Hz
(b) open at both ends?$f_{1}$ =    Hz $f_{2}$ =    Hz $f_{3}$ =    Hz $f_{4}$ =    Hz

  (a) What resonant frequency would you expect from blowing9bu/z hasa*2 ;zsac6y across the top of an empty soda bottle that is 18 ;bcyz*a9/z ssuaa62 hcm 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 ra. n7lom9kk5uk tzrk55 nge of human hearing (20 Hz to 20 kHz), what would be the range of knt 7k95r 5oulz km.k5the 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 t7cp7x )dcvf/. What willcpt7dx )fvc7/ be its fundamental frequency if it is fingered at a length of only 60% of its original length?   Hz

  An unfingered guitar string iso3o 1 yf2(rdmv 0.73 m long and is tuned to play E above middle C (330 Hz) oydrom21v3(f .
(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 orgh5 6j;gf/h sj+o j(hfgan pipe that emits middle C (262 Hz) when the temsj+h;hojj 5( g/ f6fghperature 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 24 q :t j mmsj3wc1(g(lebpkt,*0 $^{\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 showrdbq)-jz.aww+3: aeuld the hole be that must be uncovered to play D above middlezae wja- .b :r)qdww+3 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 pip clq * ;:uk /;xfr4o7tw-lopvge can resonate at 264 Hz, 440 Hz, and 616 Hz, but not at any other frequencies in between. lp f lxov; u*qwr7gko:4/;tc- (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 l c1e 98 *y9 kl:stoqugs2ly-qf;j/u8i hoe o,song is open at both ends. It resonates at two successive harmonics of frequencies 275 Hz alo og /-isce9q s:slj8ufyq2oyh,8eu;k9t *1nd 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 b-bw9ywpj/h2 $^{\circ} $ C is to be designed to produce two successive harmonics at 240 Hz and 280 Hz. How long must the pipe be, and is it open or closed?  ----待选择----closedopen  f =    m

  How many overtones are present within the audible range for a 2.14-8nn,wl0 p t+y53nklxxm-long organ pipe atxy+08np5ln3wnx l k,t 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximately 2.5 cm long. It is open to the oh; uau .2t z2aw(r.ivgutside 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 aw(tuh. g2;ur.vza2i 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 whenvqxip *1hk /m9 trying to adjust two strings, one of which is sounding 440 qh 9v1/ mi*kpxHz. How far off in frequency is the other string? ±    Hz

  What is the beat frequency if middle/48ycgf55gz 2dk vnmq 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 2)ve- b-qxb.b e3.5 kHz, while another (brand X) operates at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whine of frequency 5000 Hz occurs when they are played simultaneously, estimateb)-b-eqxb.e v the operating frequency of brand X.    kHz

  A guitar string produces 4 b;9unknen *ucz3 z.ib0eats/s when sounded with a 350-Hz tuning fork and 9 beats/s when sounded with a 355-Hz tuning fork. What is the vibrational frequency of the string? Explb.*kz n;0eni z93nuc uain your reasoning.    Hz

  Two violin strings are tuned to the same frequency, 294 Hz. Th6 3hh3wcrr2/uog;:p.7jykp czlf y*y e tension in one string is then decreased by 2.0%. What will be the beat frequency heyu3p76 o.j lyyr2f3kz/w rh* :gcp; chard 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 t 2pjna.xal/0)wts /weo play middle C (262 Hz), but one/lawt2 xj)a .n0p /wse is at 5.0°C and the other at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks, A, B, and C. Fork;16( bywjm5dh4 dsg pe B has a frequency of 441 Hz; when A and B are sounded togethj1h 5e;b4s m 6dgpwyd(er, 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 sp9 /+gjuvxo18gk5kr gkc(1f h tands 3.00 m from one speaker and 3.50 m from thecv+j(gp9/ku1k 8hr g5of1g xk other.
(a) What is the lowest frequency at which destructive interference will occur at this point? f =    Hz
(b) Calculate two other frequencies that also result in destructive interference at this point (give the next two highest). Let T = 20 $^{\circ} $C $\approx$    Hz $\approx$    Hz

  Two piano strings are supposed to be vibrating at 132 Hz, but a piano tuner hea6cdy50mz by.o 5;g3v ocvn b.xr5d.bx bo.g63yyv5omn;v0 c z cs three beats every 2.0 s when they are played 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 wavet/ .kq q9xixogipr ;ohx 7-,3wlengths 2.64 m and 2.76 m in air. How many beats per second will be heard? (Assume T =x;i7 wq x q,9tirxokg-/hp3o. 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain fire engine’s siren is 1550 Hz when 1nhayy0f 3ul 7at rest. What frequencyaf lnu3h17y y0 do you detect if you move with a speed of 30 m/s
(a) toward the fire engine,    Hz
(b) away from it?   Hz

  You are standing still. What frequency do you detect if a fire engine;0kh ecvr .e9r-k-vgx whose siren emits at 1550 He -v k;cr rkvxe-9g0h.z 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 islne,t .oq 2 u6a5pf6mg moving toward you at 15 m/s versus you g66 em25 fuq, oanp.tlmoving toward it at 15 m/s Are the two frequencies exactly the same? Are they close? $f'_{source\,movine}$    Hz
$f'_{observe\,movine}$    Hz
(b) Repeat the calculation for 150 m/s and then again
$f'_{source\,movine}$    $ \times10^{ 3}$Hz
$f'_{observer\,movine}$    $ \times10^{ 3}$Hz
(c) for 300 m/s What can you conclude about the asymmetry of the Doppler formulas?$f'_{source\,movine}$    $ \times10^{ 3}$Hz
$f'_{observer\,movine}$    $ \times10^{ 3}$Hz

  Two automobiles are equipped with the same single frequency horn. W - /lic7 idazaphy:0q0hen 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? Assuhcqi /a piday7-:l0z 0me T = 20 $^{\circ} $C    Hz

  A bat at rest sends out ultrasonic sound waves at 50.0 kHz and receives them )(kum aq , mzhdw urib34.0n,breturned from an object moving directly away from it atm q. i)aub3,n(0 w4zduk,hmrb 25 m/s What is the received sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed o65cwefu pd;1of 5 m/s As it flies, the bat emits an ultrasonic sound wave wuwefcp5d o6 ;1ith frequency 30.0 kHz. What frequency does the bat hear in the reflected wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experimentu96 +(efdpqkogtlt3 fwp0/ *js, a tuba was played on a moving flat train car at a frequency of 75 Hz, and a second identical tuba played the same 3p/wutkgf*(9f+pq0leo td 6j tone while at rest 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 waves to measure blood-flow speeds. Suppo 75n,. cptx 6)x ;tpwd tygj:hpea/t0fse the device emits sound at 3.5 MHz, and the speed 7)nw tc;,06dtx 5g/ejtf:.yxp p ahpt 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 ultrasonicgf- q9vmk r21z 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 freqy5ltv pswt9:a*h6u* zuency 570 Hz. When the wind velocity is 12 m/s from thstlu w6a vz*pyt5h: 9*e north, 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 mk h by -yfw4,flgu;,1joving on land if its speed at 20 $^{\circ} $C is Mach 0.33?    m/s
(b) A high-flying jet cruising at 3000 km/h displays a Mach number of 3.2 on a screen. What is the speed of sound at that altitude?    m/s

  An airplane travels at Mach 2.3 where the speed of sound is 310 m/s (a pnq7;ado:/h c) What is the angle the shock wave makes with the dire:7/qd;oh apc nction 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 ax3tl)3qbxxxs5j 3:3fl -t.nx iu n p2ztmosphere of a planet where the speed of sound is only about 35 mtlsxfnx3l-x 33tjni.)32u5 :bx z px q/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 travelingco/+ 9o,rxrf p 8500 m/s strikes the ocean. Determine the shock wave angle ipr+/xr , oofc9t 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 khfa/h0z2u1 ( rnh .pv v-q6es$/theta$ 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 1.5 km above thecb+j5b ujx- *b ground flying faster than the speed of sound. By the time you hear the sonic boom, the plane bjju5cxb* -+ bhas traveled a horizontal distance of 2.0 km. See Fig. 12–34. Determine
(a) the angle of the shock cone, $\theta$    $^{\circ} $
(b) the speed of the plane (the Mach number). Assume the speed of sound is 330 m/s   

  A fish finder uses a sonar device that sends 20,000-Hz sound pulses downward frotg2biy /b6a-fb:d, ijr1 q;ham the bottom of the boat, and then detects echoes. If the maximum depth for which it is designed to w;ad rhbya/2b-, q b1i:6iftgjork is 200 m, what is the minimum time between pulses (in fresh water)?    s

  Approximately how many octaves are there in the human audgg;8 v 89seyntible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display called a sewer,nb2 d3c9 fzlj ddw(r. pipe symphony. It consists of many plabncwzfr.l32 dd(9 dj,stic pipes of various lengths, which are open on both ends.
(a) If the pipes have lengths of 3.0 m, 2.5 m, 2.0 m, 1.5 m and 1.0 m, what frequencies will be heard by a visitor’s ear placed near the ends of the pipes?
$f_{3.0}$ =    Hz
$f_{2.5}$ =    Hz
$f_{2.0}$ =    Hz
$f_{1.5}$ $\approx$    Hz (Round to the nearest integer)
$f_{1.0}$ $\approx$    Hz (Round to the nearest integer)
(b) Why does this display work better on a noisy day than on a quiet day?

  A single mosquito 5.0 m from a person makes a sound /bt3yjv. qc c*close to the threshold of human hearing (0 dB). Whatq *cbj3/y vct. will be the sound level of 1000 such mosquitoes?    dB

  What is the resultant sound level when an 82-dB sound and an 8+pqj9mhjx kjdto 083:(hksf :+gg s .x7-dB sound are hearjg+(:jhks +gx .3k9opqjh 0fx8smt:dd simultaneously?    dB

  The sound level 12.0 m from a loudsp0o(rhj,e i-kid8w sn,eaker, placed in the open, is 105 dB. What is8k e0whd i, (jo,rn-is the acoustic power output (W) of the speaker, assuming it radiates equally in all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 Hz. The power output d;epp. ob go8/frops by 10 dB at 15 k8p/pb oo eg;f.Hz. What is the power output in watts at 15 kHz?    dB

  Workers around jet aircraft typically w,w*9cwy- c;itszlunx0 ;dz -t ear 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 x-sw;lz;z-cut di n,wy9t c0 *the power intercepted by an unprotected ear at a distance of 30 m from a jet airplane engine?    W

  In audio and communications systems, the gain r0ua( 50bo+ /jiukwn3tbo1lw, $\beta$ 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 t /ag1oxd ; hf+*(o1)bbkvxpjuac v. 8c4n 9cyzuned 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 wxcq+7kck s w 6bk*4*gis 32 cm long between fixed points with a fundamental frequency of 440 Hz and a mass pwg+*76*cbk4k wxcksq er 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 igniu-z.5c.+z c 9pkvf nto vibration above a vertical open tube filled with water (Fig. 12–35). The water level is allowed to drop slowly. As it does so, the air in the tube above the water level is heard to resonate with the tuning fork when the distance from the tube open9kn- cc .z5fzupv. +iging 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 zk))a b(ytqe51fgx o/ g is near 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 produ)kxb)( t zfayg1qeo5 /ce resonance (in its fundamental mode) with the third harmonic in the tube?    $ \times10^{ 2}$ N

A highway overpass was observe+8z4emhz1bif7 ri c 1)do fv2sd to resonate as one full loop ($\frac{1}{2}\lambda$) when a small earthquake shook the ground vertically at 4.0 Hz. The highway department put a support at the center of the overpass, anchoring it to the ground as shown in Fig. 12–36. What resonant frequency would you now expect for the overpass? Earthquakes rarely do significant shaking above 5 or 6 Hz. Did the modifications do any good?

  A person hears a pure mulikmi:9. w7 tone in the 500–1000-Hz range coming from two sources. The sound is loudest at points equidistant from the two sources. To determine exactly what the frequency is, the 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 soulki:i. umwm97nd?   Hz

  Two trains emit 424-Hz whistles. One train is st-zbm e0m )b() bbiqq5kationary. The conductor on the stationary train hears a 3.0-5m(qebz q-m )i)0k bbbHz beat frequency when the other train approaches. What is the speed of the moving train?   m/s

  The frequency of a steam train whistle as it approaches you is 538 Hz. Afqu *j5md :p5vcter it passes you, its frequency is measured as 486 Hz. How fast was the train moving (assume constaqcd5*j 5:mpv unt velocity)?    m/s

  At a race track, you can estimate the speed 5 yc)igxa- 2ahof cars just by listening to the difference in pitch of the engine noise between approaching and receding cars. S)gcha-2iy 5xa uppose 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 tog msrbli*crjpze)- 1p( 6u*6 dtether, produce a beat frequency of 11 Hz. The shorter one is 2.40 m long. How long ( 1je* -6c)rluir pdt 6b*zpmsis the other?    m

Two loudspeakers are at opposite ends of a 8q8jn:d2; km lnsogp2 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) he listens from the position A, in front of the car, (b) he is between the speakers, at B, an ;nj2 :plqgndo82sk8 md (c) he hears the speakers after they have passed him, at C?

  If the velocity of blood flow inp-u ;u v*lr3s g*qj3o wr6oqvt lppa6iz)*90f the aorta is normally about 0.32 m/s what beat frequency would you expect if 5.50-MHz ultrasound waves were directed along the flow jrvpv6g6zw llr psioqa*u)*03 3*qu t-;f9p oand 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 while the moth is flyin yz5grmu7b)cn1)e(m e4zmnbi 51dr7 p2 yy5owg toward the bat at speed 51) o145d y ) n cuen5wzz7ey2 mbribypmgr5(m7 m/s The bat emits a sound wave of 51.35 kHz. What is the frequency of the wave detected by the bat after that wave reflects off the moth?    kHz

  A bat emits a series of high frequency sound pulses as it approaches a mu swvj6k,;.n-im r 3sz: uynn2oth. The pulses are approximately 70.0 ms apart, and each is about 3.0 ms long. How far away can the moth be detected by the bat so that the echo from one chs-i3:nknm; uwz unr6 v 2yj,.sirp returns before the next chirp is emitted?    m

The “alpenhorn” (Fig. 12–38) was once useo8qsz7h c8l0t -cbv*zuy:2xzd to send signals from one Alpine village to another. Since looqz- :bhs y*zux c28lvz0tc87 wer frequency sounds are less susceptible to intensity loss, long horns were used to create deep sounds. When played as a musical instrument, the alpenhorn must be blown in such a way that only one of the overtones is resonating. The most popular alpenhorn is about 3.4 m long, and it is called the F sharp (or G flat) horn. What is the fundamental frequency of this horn, and which overtone is close to F sharp? (See Table 12–3.) Model as an open tube.

  Room acoustics for stereo listening can be compr,,+gmzohdt ;i)4sbd domised by the presence of standing waves, whicmb +4dihtg ,;z sd)do,h can cause acoustic “dead spots” at the locations of the pressure nodes. Consider a living room 5.0 m long, 4.0 m wide, and 2.8 m high. Calculate the fundamental frequencies for the standing waves in this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

  A dramatic demonstration, cagc ,3e ywiqs j*p t75bqubc5(5lled “singing rods,” involves a long, slender aluminum rod held in the hand near the rod’s midpoint. The b(57qsp eybt wc3j*5quigc ,5rod 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 tg1ojc 2(/d t0upbeoy 7hreshold of hearing for the human ear at a frequency of about 1d( 72e /bucgojotyp01000 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 obsmggn3q8p /yx6erver on the ground hears the sonic boom 1.5 min after the plane passes directly overhead. What is the plane’s altitudemxgy/g38p 6qn ?    $ \times10^{4 }$ m

  The wake of a speedboat is v, ny atj i-ucf:il c;t7;fd8t )r -qa;cdy2n915 $^{\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