What is the evidence that sound tramm1.lqkt3ww32wh j5gvels as a wave?

What is the evidence that sound is a form of en:j *mp8gz4nn3;je u8hakl8 .w0v knoqergy?

Children sometimes play 8ys aqri(8ry*with a homemade “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 sounsiarq(r *8yy 8d wave travels from one cup to the other.

When a sound wave passes from air into water, do you expect the fi7 glj y uhk/i85bgh0:ah)c v*requency or waveleng/ vaghk)7jb 0c:5iuyg8 l*h hith to change?

What evidence can you give thah:vawn- t0f8(a/szq+ ocu/p v clq:r+t the speed of sound in air does not depend significantly onvvpn t+qs l+(/-u/fao::zh rcwa8c q0 frequency?

The voice of a person w dw.qwzf(;d b9ho has inhaled helium sounds very high-pitched. Why?

How will the air temperature in a room affect the pitch of orgfg9psz+-,c r+2uuz e ywl5tf9 an pipes?

Explain how a tube might be used as a filter to rn2ttc /x oi;x,educe the amplitude of sounds in various frequen; ,t/oxnit x2ccy ranges. (An example is a car muffler.)

Why are the frets on a guitar (Fig. 12–30) spaced closer together as yo; dnq /dh*wp4yu move up the fin; wp dyh4d/qn*gerboard toward the bridge?

A noisy truck approaches you from behind a builw xnxbyjgs5j j0 /89*f a-wma/ding. Initially you hear it but cannot see it. When it emerges and you do see it, its sound is suddenly “brighter” — you hear more of the high-frequency noise. Explain. [Hint: See Section-xja/fwj 8 am gj*05bn9/xsw y 11–15 on diffraction.]

Standing waves can be said to be due to “interference in space,” whereas beatc 0 qb7h08zbxcs can be said to be d08 xc7hcbzb0q ue to “interference in time.” Explain.

In Fig. 12–16, if the frequency of the speakers were lowered, woulkjfu w 9(-rl2nd the points D and C (where destructive and constructive interference occ kunrw-lf(j 29ur) move farther apart or closer together?

Traditional methods of protecting the hearing of people who work in areu/,ee u6h sxn/as with very high noise levels have consisted mainly ofx e/nu ush/e6, 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 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 waveo:cb pcn/ /38r 8hrngm can be thought of as a superposition of two sound waves with slightly different frequencies, as in Fig. 12–18. In g hb /:onr 8cp3rcm8/nwhich 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 theu5 ra9fg le,m3 same direction, with the sam5rl,u9 3emg fae velocity? Explain.

If a wind is blowing, will this alter the frequency of the souzj .*gs:yqd)r7pcye. l8 l 2stnd heard by a person at rest w2jz.* py) :csld8rq t7g.s eylith respect to the source? Is the wavelength or velocity changed?

Figure 12–32 shows various positions of a child in motion on a swing.k w6y:) -t1wv h n/,tpyka1uub A monitor is blowing a whistle in front of the child on the ground. At which position, A through E, w /1b-w a1k t)upknyt,y:6hv wuill the child hear the highest frequency for the sound of the whistle? Explain your reasoning.

  A hiker determines the length of a lake by listt3,3noqdik e(ening for the echo of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.0 s o,e3nd t( qki3after shouting. Estimate the length of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes thec6 j q7wi+t;8*njxt fq side of 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 ocean at this point? Assume the speed of s8cqt7 w*xi6fqjj +t;nound in seawater is 1560 m/s (Table 12–1) and does not vary significantly with depth.    $ \times10^{ 3}$m

  (a) Calculate the wavelengths kztu( 8y9w ( me+ l(5attikb1(b rhf9zin 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 tui kt-w )is.vmpo0lyaaw5 ;/.ana on a foggy day. Withouta5;vw i a aytil-k.0/wp.som) 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 fish,    s (b) by the fishermen?    s

  A stone is dropped from the top of a cliff. The spl(lr;h:mt5s/ti 3 l lavash it makes when striking the water below is heard 3.5 s later. How highvltsli3a :5/ ht(lmr; is the cliff?    m

  A person, with his ear to the ground, sees a xv*- w2mzqa(u 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 concre(xwau2m q -z*vte, 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-secln 4-a8(wt ,n ymi(ibwond rule” for estimating the dis(ilwb4at m(wy,8 n-i ntance 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 lev.nsy*h7u jln:el 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 sg4z6 rr8 1 e4s00wc/vrv/rusc cj n2ccound whose intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound level of 95 dB when fired simultaneouslyeyf0.b+i zmwlg2(mr ye 8f;2r at a certain place, what will be thl be(z;g0f+mmy28f er yr2 .wie 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 exgbdeg12.4 r yqually noisy jet engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person experience if the captaiyb1de.4rg2 xgn shut down all but one engine? [Hint: Add intensities, not dB’s.]    dB

  A cassette player is said to have a signal-to-noise :,ff8 vk3-4ivk tp ivzratio of 58 dB, whereas for a CD vtfki38v 4zvf-:pi,k player it is 95 dB. What is the 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 speaking in nore.s s 97ysunyr a28v:smal conversation. Use Table 12–2. Assume the sound spreads rougus .yvs yeasn7s8 9r2:hly 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 w 4y0zt,0mxhao c 4mp09 kzvk)5 1ovniihose 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 modest am.oflo3b2 e5yeb :ch 0splifier B is rated at 40 W. (a) Estimate the sound level in decibels you would expect at a point 3.5 m from a loudspeaker connected in turny.e 50slbo2beo3c: hf 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 placed 2.8 m in front ohe-7g8 2a; fvdnlqk5ctiz7 h(f a loudspeaker on the stage7h2qlantd;(h v 8c if-gz75ke.
(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 leverg67 e)uvp7a,rz)x ,1o rldpel of 2.0 dB. What is the ratio of the amplituloge7zrpr1 7)u,a)e6xv,r dp des of two sounds whose levels differ by this amount? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound wave u8n-a 0bwvk2 ris tripled, (a) by what factor will the intensituwv kn r0a8-b2y increase? Increase by a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal disp1 x,y de(fymz,lacement amplitudes, but one has twice the frequency of the otherxf ,myze,1 d(y. What is the ratio of their intensities?   

  What would be the sound level (in dB) of a sound wave in air that corresdki5co 7d 1rb-psr9a 1ponds to a displacement amplitude of vibrating air molecules of 0.13pc1db 95a rr1o-7isdk mm at 300 Hz?    dB

  A 6000-Hz tone must haa0a- riq,qzv -ve what sound level to seem as loud as a 100-Hz tone that h a,aqizv --0qras a 50-dB sound level? (See Fig. 12–6.)    dB

What are the lowest and highest frequencies that an earwv:0qn)c)1s p k)plcmckcr.5 can detect when the sound level is 30 k51 ccqp p w. cvr)nsml0c))k:dB? (See Fig. 12–6.)

  Your auditory system can accommodate a huge range of sound levels. f zeb5r-b1oe65k;vp z 8afza vkwrl1z27r: 5yWhat is the ratio of highest to lowest o kz5abf e7fewb552r:yvl 61pz-8k ;rr1vzazintensity 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 fundamental5hsmxuku-,qgv+*3q 6d) z srh frequency of 440 Hz. The length of th s,uhhg35ud )qk6 m-+vqr*zsxe 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 the fundamental and first three audic07,vu a h(prable overtones if the p(c, pavh07rauipe 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 expect1rd qpfnc6uzeo,c il0h( .;b ploe 21, from blowing across the top of an empty soda bottle r,6o,lbqfup;dhe 2z(1 i .n 1pecocl0that 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 pipm *zk+*; cde-paog:(:p id sples spanning the range of human hearing (20 Hz to 20i:+cp*als*( og zppm; d :dke- 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 th8dz(1 xmjxc4 wird harmonic. What will be its fundamental frequency if it is fingered at a length of only 60% of its (m 418xxzwdjc original length?   Hz

  An unfingered guitar string is 0.73 m long and is tuned to 2 1ctlgrr96rb(z*, haak rxv+play E above middle C , 6 * gtrvr(rbaczx+19ka2rlh (330 Hz).
(a) How far from the end of this string must the finger be placed to play A above middle C (440 Hz)?$\approx$    m
(b) What is the wavelength on the string of this 440-Hz wave? $\approx$    m
(c) What are the frequency and wavelength of the sound wave produced in air at 20°C by this fingered string?    Hz    m

  (a) Determine the length of an ogi 2ba5+r.*xkr 9ish;s+v r dnpen organ pipe that emits middle C (262 Hz) when the temperature isd9v;inrr5 g2+s+*s .hxb irak 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 5gzhs;6 lpw1nat 20 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece of the flute in Examhy,cj. 6y/m luple 12–10 should the hole be that must be uncovered to play D above middle C, /juclmh6y.y 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 reson4nk.i o-asza2m0lx r ,ate at 264 Hz, 440 Hz, and 616 Hz, but not at any other frequencies in between. (a) Show why this is an open or a closed pipe.aikla 0 2.n,xz -sr4mo ----待选择----closedopen  (b) What is the fundamental frequency of this pipe?   Hz

  A uniform narrow tube 1.80 m long is open av5xpk9j .ig6x, il4b ct both ends. It resonates at two successive harmonics of frequencies 275 Hz and 330 Hz. What isi ckibj9g ,xvp4l65. x
(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 4k/1v nl2wr:8oc ldyc$^{\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-m-long kq :wb q/e4e0horgan qh40 qew:ke/b pipe at 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximately 2.5 v28ijf:l;o * 0g*o jrs6p gg3eg.wrzrcm 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 thrr**jl 2i0r ow:g;eg3ovgf6gj z.sp 8e information in the graph of Fig. 12–6? $f_1$ =    Hz $f_3$ =    Hz $f_5$ =    Hz

  A piano tuner hears one beat * 76p)*lmpg vw7mxh qbevery 2.0 s when trying to adjust two strings, one of which is sounding 440 Hz. How far off in fr*l p 7wxv*qp67m )ghmbequency is the other string? ±    Hz

  What is the beat frequenq6vdy) y+ nun/cy if middle 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 operat.y uf spw9pk6+es at 23.5 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 fywpk6.9+ ps uare played simultaneously, estimate the operating frequency of brand X.    kHz

  A guitar string producn / 15mpujetjuy11jk/es 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 the vibrational frequency omj/ pjjutyn 1k e/11u5f the string? Explain your reasoning.    Hz

  Two violin strings are tuned to the same frequency, 294 H .n0 +h pt01hvsdmr-)1ykm1 udc clt*ez. The tension in one string is then decreased -sp h1 tlu n)cmrddkty e.+1ch100vm*by 2.0%. What will be the beat frequency heard when the two strings are played together? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be heard if two identical flutes e1he(ur .+afzw0+jlb;fa -ys+ fy5v ldach try to play middle C (262 Hz), but one is at jfvhlzy1 bafdl +(eu-w+;.+yfra0 5s5.0°C and the other at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks, A, B, and C. Fork B has a frequency of 441 Hz;1w.de8 0ajj0x3k 8 n poccj,8u4dhkll when 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 Cj l e 3o cnh,k4d1xua p0kjwjd808cl8.? 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 o:qkgh pb(h4g3 ne speaker and 3.50 m from the other. (pgh3:h bqk4g
(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*wd rd-hs6vh78f qp7q 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 hsd7rdhfp -w*786v qq 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 2.76 m in air. Hobjtrs9aw4 (p .z hm6:rw many beats per second will be heard? (Assumh. r4zwa jrst(b6:pm 9e 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 ati2hb c27+ nlmv rest. What frequency do you detect if you movlmb ih22c+7 vne with a speed of 30 m/s
(a) toward the fire engine,    Hz
(b) away from it?   Hz

  You are standing still. What frequencyxqe3 fd9vf aul2o -i (:k,wllt)j-ibszt,3 *w do you detect if a fire engine whose siren emits at 1550 Hex s zia *(vlt2f iltd3juwwbq -kol9:,f -3,)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 4foo(6fko4o *vph3 yt is moving toward you at 15 m/s versufy ookf(6hvo4to 34 *ps you moving 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 freque+ 7a7a,ri 45y axf+p:etcrodancy horn. When one is at rest and the other is moving toward the ftr++iaca5 :7 x7raf a, ydpe4oirst at 15 m/s the driver at rest hears 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 kHz and receives them qx,8e+5wv d5az(n g mfz.+afureturnedw +5vfm,qfz8u5(a zgxa +.ned from an object 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 5m/r9o z hksr(* m/s As it flies, the bat emits an ultrasonic s/9ro*sh m kz(round wave with frequency 30.0 kHz. What frequency does the bat hear in the reflected wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experiments, a tuba was played on a moving l,.;aw ojl h*bflat train car at a frequency of 75 Hz, and a second identical tuba played the same tone while at rest in the railway station. What beat frequency was heard if the train car approached the station at*whblj o;,l .a a speed of 10 m/s ?   Hz

  A Doppler flow meter uhe7v0y5ii k;b8 /ptjises ultrasound waves to measure blood-flow speeds. Suppose the device emits sound at 3.5 kpebtji /iv78h i50y;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 ultra*4/rq mtt:ucj j ;c9yhsonic waves of frequency $2.25 \times10^{ 6}$Hz is used to monitor the heartbeat of a fetus. A (maximum) beat frequency of 500 Hz is observed. Assuming that the speed of sound in tissue is $1.54 \times10^{3 }$ m/s calculate the maximum velocity of the surface of the beating heart.    m/s

  A factory whistle emits sound of frequency 570 Hz. When the wind velocix:7scka 2du d8ty is 12 m/s from the north, what frequency will 27usad8 :kcxd 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 movrgy*(-mpwy v5yln psfn m8*xu;a o7* /ing 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 2.3tm4pxuqk y 9168pir ,d where the speed of sound is 310 m/s (a) What is the angle the shock wave makes with the direction of the airplarum8,ki p 6 t4dq9yxp1ne’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 thinx nx9:0q2b reo atmosphere of a planet where the speed of sound is onl xqb :onx20e9ry about 35 m/s
(a) What is the probe’s Mach number if its initial speed is 15000 km/h$\approx$    (Round to the nearest integer)
(b) What is the angle of the shock wave relative to the direction of motion?    $^{\circ} $

  A meteorite traveling 8500 m/s strikes the ocean. Determine th ju9sp:-hdac99 jyoopas 38z 0e shock wave angle it propas3o s8 yhd jau9-09:9cj ozpduces
(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 i6hgkcdy:wx 4ck/, l0$/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly overhead and see 3d.czru)q+v+ 8 gabix 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. 12–34. Determinvaz+. +br )8qdui xg3ce
(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 downwardb- *h6 ;qsyzr osl1o0c(er .ksgh9bd7 from the bottom of the boat, and then detects echoes. If the maximum depth for whicho s 6z kc(ers.ohsbl *yr-71;9hqdbg0 it is designed to work is 200 m, what is the minimum time between pulses (in fresh water)?    s

  Approximately how many octaves ar + b(l.o.3kfrc zyt-uae there in the human audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a displayj bu*d7tgf2lvy,qr6 s4sg)(f called a sewer pipe symphony. It consists of many plastic pipes of various lengths, which are open on both e)y(f *2ds7t6,v4 fjrqg bglsunds.
(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 2vhw87pk s0(7 pakcu vclose to the threshold of human hearwv7 up7ch80kvp(as k 2ing (0 dB). What will be the sound level of 1000 such mosquitoes?    dB

  What is the resultant sound level when an 82-dB sound and an 87-dB sound are hea 2pu d70u m.+bvat tsk7l-t5uxrd simu7kp0m5t l7u. +axub2ttsudv-ltaneously?    dB

  The sound level 12.0 m from a loudspeaker, placed in thqsdv1p)i4e6 , 4fqaige open, is 105 dB. What is the acoustic power output (W) of the speaker, assuming it radiates equally i6 i 4aqg4i ve)f,dsqp1n all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 4g.m* /t fuy adjef qsxp70 d9ikf:1k/Hz. The power output drops by 10 dB at 15 kHz. What is t d1eu9. sy/ tf i0/kmg:4ffqx*dapkj7he power output in watts at 15 kHz?    dB

  Workers around jet aircraft typically wear q8ku y2bxnzecay7)aswk968 :/*vwff 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 poweryq:e/b6f 8c7k nzw vyfkas ax u98)w2* intercepted by an unprotected ear at a distance of 30 m from a jet airplane engine?    W

  In audio and communicaqev1yt uve-g+.n0 n y(tions 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 violin is tuned to askpi gek*2 64w 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 vioy rxl ca3,6y,plin is 32 cm long between fixed points with a fundamental frequency of 440 Hz and a mass per unit length ofc3 , axryypl,6 $6.1 \times10^{-4 }$ kg/m
(a) What are the wave speed and tension in the string?    $ \times10^{2 }$ m/s    N
(b) What is the length of the tube of a simple wind instrument (say, an organ pipe) closed at one end whose fundamental is also 440 Hz if the speed of sound is in air?    m
(c) What is the frequency of the first overtone of each instrument?   Hz    Hz

  A tuning fork is set into vibration above a vertical open tumy( ,7ph,fw / h9id1aqakhr.tbe 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 wat wtakh.h 7 mpd9haqyi,/(,1rfer level is heard to resonate with the tuning fork when the distance from the tube opening to the water level is 0.125 m and again at 0.395 m. What is the frequency of the tuning fork?   Hz

  A 75-cm-long guitar string of mass 2.10 g is near a tubmy45xzkbgzoy -99 :ww e that is open at one end and also 75 cm long. How much ten 5zx9wobg ywk-:z y9m4sion should be in the string if it is to produce resonance (in its fundamental mode) with the third harmonic in the tube?    $ \times10^{ 2}$ N

A highway overpass was observed to resonate as one pukg7 l9rnwrcwm2 t-;e;y*p0 full loop ($\frac{1}{2}\lambda$) when a small earthquake shook the ground vertically at 4.0 Hz. The highway department put a support at the center of the overpass, anchoring it to the ground as shown in Fig. 12–36. What resonant frequency would you now expect for the overpass? Earthquakes rarely do significant shaking above 5 or 6 Hz. Did the modifications do any good?

  A person hears a pure tone iks4b (gx9m2ji n 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. km4 sb 9gix(2jWhat is the frequency of the sound?   Hz

  Two trains emit 424-Hz whistles. One train is stationary. The c zxn;dcu *x)b*onductor on the stationary train hears a 3.0-Hz beat frequency when the oth d;cx)*ub*znx er 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. Afs7f 4gtw h.8n xs0trw.ter it passes you, its frequency is measured as 486 Hz. How fast was the train moving (assume constr7wnxws.htt04f s8g .ant velocity)?    m/s

  At a race track, you can estimate the speed oftaq:unb5 uqc)5 m7a( q xz/w)d cars just by listening to the difference in pitch of the engine noise between approaching and receding cars. Suppose the sound of a cert:wn x)b 5auu5/cq d)7q(mz qtaain 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 frequency of 11 Hz06l u-xm++ nu4 a jporzqfb*4z. The shorter one is 2.40 m long. H ufnz-0ox4zl+ b mr*u64pqja+ow long is the other?    m

Two loudspeakers are at opposite80+n/ jl.m w dpsfys+ 3gzi0x 0z;zesx ends of a railroad car as it moves past a stationary observer at 10 m/s as shown in Fig. 12–37. If the speakers 0p+m0yjwz+ xsl;nzxs z /e gf3 i.08sdhave 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 (c) he hears the speakers after they have passed him, at C?

  If the velocity of blood flow in the aorta is n. zt 3mt/ +i6f2reutg2 ww+ijkormally about 0.32 m/s what beat frequency would you expect if 5.50-MHz ultrasound waves were directed ag+mk3 ue22z.tfj+/w i witrt6long the flow 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 /,t6 0jltgx -+ gv3 wd/usdxevspeed 6.5 m/s while the moth is flying toward the bat at speed 5 m/ts gewdj0,xt6vg-/ld3vu +/xs 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 sw5b;+3sp 4f;72sor padyrdpvound pulses as it approaches a moth. The pulses are approximately 70.0 ms apart, and each is about 3.0 ms low +pr bs47adf pyps2;;3 rodv5ng. 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 from one Al-: :fywix3yshh8tzg;pine 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 t3i:g8 hxs yzhfy-w;: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 sh x++ne(8wd au )3mescan be compromised by the presence of standing waves, which can cause acoustic “dead spots” at the locations of the pressure nodes. Consider a living room 5.0 m xns su dm+aw3eh8+(e)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 “singingt/t,lzbn7 k w2 rods,” involves a long, slender aluminum rod held in the hand near the rod’s zl 7bk,tntw/2midpoint. 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 thgs4 zcgtp-bm8) lg+w+reshold of hearing for the human ear at a frequency of about+b8lg+ wzt)p-4 ggc ms 1000 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 ghtm hlj093o ,jl zp 7jp3sn;/observer on the ground hears the sonic boom 1.5 min a,33g jh p/p7lj 0jhtmloz;n9sfter the plane passes directly overhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboat is 15 /i3-y)s8)3m bylpvhba+ *qq cpqc xe;r3wyw7$^{\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