What is the evidence that.mxcy*blf9yuf 2)6 rtpwxa3( sound travels as a wave?

What is the evidence that sound is az gkhmb 6o(/h; form of energy?

Children sometimes play with a homemade “telephone” by at+7izd4x1wodz v m7yd+u h, l ((fvvma0taching 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). Explai+ovy (fw7 md1mv+l iz70x,4 zhdd ua(vn clearly how the sound wave travels from one cup to the other.

When a sound wave passeb3u8*fsbw5 ry s from air into water, do you expect the frequency or wavelength to chab3*srf85 y uwbnge?

What evidence can you give that the speed of sound 9sz1l n0mzf/7yhle d.in air does not depend significantly on freque.fd0nmlz 1 z7/se9 lhyncy?

The voice of a person who has inhaled helium sounds verybx9ah2 6dd r0w high-pitched. Why?

How will the air temperature in a room affect the pitch of organ 8r/sb y2wziyi 1qwh1 +l. nyqkh8z*g,pipes?

Explain how a tube might be used as a filter to reduce the amplitude 7vzr zaw1tm)9 of sounds in vari r 1awmt)zv97zous frequency ranges. (An example is a car muffler.)

Why are the frets on a guitar (Figl /-9kn 5;wmpvl lz1nb)*ejm 7hlyoa6. 12–30) spaced closer together as you move up the fingerboard toward the brid* l ll)v5yz kb6/j9w ;lnoe-1mah mn7pge?

A noisy truck approaches you from behind a building. Initially ypkmn5+g --yd lq a;m3gef e8r3ou 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 11–15 on3 q k g5-aemd +m;eflnyr3g-8p diffraction.]

Standing waves can be said to be due to “interference in space,” whereasd5lnc--t5 ;px- dpo wv-yax7z beats can be said to be due to “interference in time.” Expla7 x5yx 5-n-tld ;-a-dvp cwpozin.

In Fig. 12–16, if the frequency of the speakers were lowe.3ifr7 /fs d+nly 3cyuiu-k x2red, would the points D and C (where destructive and constructive intlx 7 cifu3. 3d+2ny/fkr syiu-erference occur) move farther apart or closer together?

Traditional methods of pr:0usf-mknsg9 v:zexdfk ; d 6,otecting the hearing of people who work in areas with very high noise levels have consisted mainly of efforts to block or reduce noise levels. With a relatively new technology, headphones are worn that do not block the ambient noise. Instead, a device is used which detects the noise, inverts it electronically, then feeds it to the headphones in addition to the ambient noise. How could adding more n,s0n:u x gmf-d6;v s9kdkefz:oise reduce the sound levels reaching the ears?

Consider the two waves scwy)kk1+3*td,i;7 vexl p sr +d,l ladhown in Fig. 12–31. Each wave can be thought of as a superposition of two sound waves with slightly different frequencies, as in Fig. 12–18. In which of the waves, (a) or (b), are the two component frequencies farther apart? Exl1wi,l3esd),x +t *k adyrkv; +dclp 7plain.
(12-31)
(12-18)

Is there a Doppler shift if the sorrptmspkc67q .cel e 43m4(c7urce and observer move in the same direction, with the samsrce7p.3tlkc qe 44prm7cm( 6 e velocity? Explain.

If a wind is blowing, will this.m b90uo( saku alter the frequency of the sound heard by a person at rest with respect to the soa.ms 0ou (k9buurce? Is the wavelength or velocity changed?

Figure 12–32 shows various positions of a child in motion : aikgpi.j-w 05dio/ion a swing. A monitor is blowing a whistle in front of the child on the ground. At which positii.go5: da0ii iw /j-kpon, A through E, will the child hear the highest frequency for the sound of the whistle? Explain your reasoning.

  A hiker determines the length of a lake by listening for the e) ouh cz+5/ tmvz*qz9jcho of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.0 s after shouting. Estimate the length of the lake5+c)z9qu /zvoj h*zm t. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship just below the waterline. He hears thawj1v+1e1hbd e echo of the sound reflected from the ocean floor directly below 2.5 s later. How deep is the ocean at this poa1w 11 vjed+bhint? 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 eg1: 5-yj)ikpcl+n rbin 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 qh mp 3 ;ej-693ppuwotabove a school of tuna on a foggy day. Without warning, an engine backfire occurs on another boat 1.0 km away (Fig. 12–33). Hj h3to9p3mwq-eup; 6p ow much time elapses before the backfire is heard (a) by the fish,    s (b) by the fishermen?    s

  A stone is dropped from the top of a cliff. The splash it makto ) mvtxy k)6yyj/8r-es when striking the water below is hear) - 86rv /yjk)tmyytoxd 3.5 s later. How high is the cliff?    m

  A person, with his ear to the ground, sees a huge stone strike the co7;2o( zre snjrncrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other in the conr je72no sr(z;crete, 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 bul3w ci5 y 2lo1v+: diqmx2l9cp/5njhy the “5-second rule” for estimating the distance from a lightning strike22w ilvo :1pmlqcl5hxn+idj/35c 9 yu if the temperature is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity of a s c l7rn:e mg).ch)aq3vound 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 as1la teo7b7jb7r k0 4;3niglintensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound level y1je0w6 kwq0eof 95 dB when fired simultaneously at a certain place, what will be the sound level ie0 1kwwq jy06ef only one is exploded? [Hint: Add intensities, not dB’s.]    dB

  A person standing a certain distance from an airplane with four equally b*1to vk,hhx9 noisy jet engines is experiencing a sound level bordering on pain, 120 dB. What sound level wouldb, 1hvkhx 9ot* this person experience if the captain shut down all but one engine? [Hint: Add intensities, not dB’s.]    dB

  A cassette player is said to have a signal-to-noise ratio oi /z/ s tvlq+a4tog2,xf 58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensities of the signal and the background no+tv stz qg//al 2io,4xise for each device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of sb,wpfy1 x5llgao *0jdhno::3f;n +yt2i et. bound from a person speaking in normal conversation. Use Table 12–2. Assume the sound spreadsib f l0pgt:lh.;2fbn+eot d:aoyw*1xj3 n5y, 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 whose arey+0pvuy-d q1zvo 14qia 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, whie0vjc*:hj k v2h4 ms4zle the more modest amplifier 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 turn to each a20jhvkzvh s*m:ce 44 jmp.$I_{250}$ =    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 ckol ); my:dz6 *r6yubdB when placed 2.8 m in front of a loudspeaker on ty k:umdbzc y66r;)l*o he 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 typically2 ,n;.ev. iil rb: oahlxq1m i,n4v,ia detect a difference in sound level of 2.0 dB. What is the ratio of the amplitudes of two sounds whose levels differ by this amouni1.4h,:rim l.qanix, l avvoi2 ;, bent? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound wave is triplf*iicj y(,*fk ed, (a) by what factor will the intensi,c(if*j*y fk ity increase? Increase by a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal dikjm).b mh(n (isplacement amplitudes, but one has twice the frequency of the other. What is the ratio .kb)(inm jhm( of their intensities?   

  What would be the sound level (in dB) of a soukn :/x5pb* bnpnd wave in air that corresponds to a displacement amplitude of vibrating air molecules of 0.13 mm at 300 Hz?x /pb bn*pn:k5    dB

  A 6000-Hz tone must have what sound level to seem as lou5:qbjob:/fgm d as a 100-Hz tone that has a 50-dB sound level? (See Fig. 12/b qmgj bf:5o:–6.)    dB

What are the lowest and highest frequencik z06v.)yl1-hhhuv t u2m /n r;fua:fdes that an ear can detect when the sound level is 30 dB? (See z/ln u:h6 hvm1u)02kfyrt f.-u d vah;Fig. 12–6.)

  Your auditory system can accommodate a huge range of sw0dcj :s;+fsw ound levels. What is the ratio of hfc : w0+sdjws;ighest to lowest intensity at
(a) 100 Hz,$ \times10^{ a }$ a =   
(b) 5000 Hz? $ \times10^{ a }$ a =   
(See Fig. 12–6.)

  The A string on a violin has a fundamental freq4ob*i y ungu.k+ac 9:quency of 440 Hz. The length of the vibrating portion is 32 cm, and it has a mass of 0.35 g. Under what tensioncib.4g9q +:ok unuy*a must the string be placed?    N

  An organ pipe is 112 cm long. What are the fundamental and first4vtvd)(0 d5j(n/c( fosy ptvk three audible overtones idf ot)kpcvnv((d y(js0t5/ 4vf the pipe is
(a) closed at one end, $f_{1}$ =    Hz $f_{3}$ =    Hz $f_{5}$ =    Hz $f_{7}$ =    Hz
(b) open at both ends?$f_{1}$ =    Hz $f_{2}$ =    Hz $f_{3}$ =    Hz $f_{4}$ =    Hz

  (a) What resonant frequency would you e,hczo0op ug (0xpect from blowing across the top of an empty soda bottle that is 18 cm deep, if you assumed it was a closed tube? (hoguoz0p,0 c    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:qac4dt kz s8hoba9 1 +mfk,*hge of human hearing (20 Hz to 20 kHz), what would be the range of the lengths of asf491,c 8dm +kah*t: zobkqhpipes required? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

  A tight guitar string has a frequency of n.bxo22 /d+oo7ipy5pug .ut+kf d (t n540 Hz as its third harmonic. What will be its fundamental frequency if it is fingered at a length of only 60% of its original leno2+ f.x+yk5bddn/ u og2 pot(tuni.7p gth?   Hz

  An unfingered guitarok(cx lhy) c m:7zd*y6 string is 0.73 m long and is tuned to play E above middle C (330 Hz)oy: c7h *dl( k)zyxcm6.
(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 u39 z 1ihv v6vs1rv5az30p:hpd2 cllgorgan pipe that emits middle C (262 Hz) when the temperature is 21iza0hz1s5drvvpu 2cpv l lh393 v61:g $^{\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 2t f* qfb;hptxk sbr*);vsp45:0 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece of the o:(zg8bf)zbt0 r*hh hflute in Example 12–10 should the hole be that must be uncovered hh *f0zbr)gt8(h :bzo 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, and 616 Hz, butb/ttil .1g t.a not at any other frequencies in between.1tti. /b gtl.a (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 botw -y5jh9fwil( g(jmj(h ends. It resonates at two successive harmonics of frequencies 275 Hz and 330 Hz. What is i-lw j(hjw ( 59jyfm(g
(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 jn +kxoqqllv -1l2; (r$^{\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 audibln(m-refx, yj5 e range for a 2.14-m-long organ pipe at 20 y5jmr enx (-,f$^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximately 2.5 cm long. It imkw 7:fh- 5mzhs open to the outside and is closed at the other endk h5 wh7m:-mfz 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 beatyf)xle9nte; z vf3l2)i cp:x5 every 2.0 s when trying to adjust two strings, one ozyv3)e: )x5xn iflcp29 ltf e;f which is sounding 440 Hz. How far off in frequency is the other string? ±    Hz

  What is the beat frequency iye 5* dam6 -gh y)t0n3ut*oeatf 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 operates at qd /xgi+-hi (0(fza wv23.5 kHz, while another (brand X) operates at an unknown frequency. If neither whistle can be di gvz0 x-ia(/hwqf+( heard by humans when played separately, but a shrill whine of frequency 5000 Hz occurs when they are played simultaneously, estimate the operating frequency of brand X.    kHz

  A guitar string produces 4 beat:tjpl 7k +lr; w4gdy,n*-iks ts/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? +4inlgtpy dl r k,w-7;tsk:* jExplain your reasoning.    Hz

  Two violin strings are tuned to the same frequency, 294 Hzf7vl 5 98dzw7tn5(bveeyd(c):wlai m. The tension in one string is then dec7vldc7 8fedi( :yv5n)twmzw (5ab l9ereased 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 tw6xfz *:y)wczo o identical flutes each try to play middle C (262 Hz), buzw6z*ycxf)o :t one 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 B has a fwmho/blk. p02requency of 441 Hz; when A and B are sounded together, a beat frequency of 3 Hz is heard. When B and C are sounded together, the ml w/pbkho0 2.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 stjyf 2a7;(xsig */lshu ands 3.00 m from one speaker and 3.50 m from tauh2ly/s7g(*; ixfj she 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 q*rt7juff4l :pm rx7, to 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 b:r 4f pum qjl*,7fxrt7e 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. Howqw 9tr ,,t +vz9wosh)g many beats per z) ,,g9+vt wrhsq9wto second will be heard? (Assume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certa rmk*qcg8/5 rwin fire engine’s siren is 1550 Hz when at rest. What frequency do you detect if you move with kqm5w/r8g *cr 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 whose 4t x.bjm k.kp2oe*r9,nygqw 7siren emits at 1550 Hz moves at a speed of 32 gyrpmqt,.xon .2wkekb9 *j 47m/s
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift iaph egt b -hjo,pc2 2+vp9vn3*n frequency if a 2000-Hz source is moving toward you at 15 m/s versus you moving toward it ao*h-jve9tc 2g +pna2p p3b h,vt 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 fre9mkcnv;1g* 1 o+zi- u k8r6h9l8:omc izjqihuquency horn. When one is at rest and the other is moving toward the first at 15 m/s the driver at rest hears a beat frequency of 5.5 Hz. What is the frequency the horns emit? 1j8k zmcmk +g*9h;v9ur:q conlhii6 uo-i18zAssume T = 20 $^{\circ} $C    Hz

  A bat at rest sends out ultrasonic sound waves at :f3m*nqlbrc3jvv( w: 50.0 kHz and receives them returned from an object moving directly away from it at 25 m/s What is the rv vr:qfmw33:b n(l *cjeceived sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed of 5 m/s As it flies, the bat emits an dkbx q 003uy4xultrasonicxqdbxu 3y04 0k sound 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 expero luoc*yl /-*oiments, a tuba was played on a moving flat train car at a frequency of 75 l/* looo*yc-uHz, 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 a speed of 10 m/s ?   Hz

  A Doppler flow meter uses ultrasound w4 id-b uv3+:szm4eli m,-q kntaves to measure blood-flow speeds. Suppose the deebv-u4,nl4z+:ik mq - m sitd3vice emits sound at 3.5 MHz, and the speed of sound in human tissue is taken to be 1540 m/s What is the expected beat frequency if blood is flowing in large leg arteries at 2 cm/s directly away from the sound source?   Hz

  The Doppler effect using ultrasonic)ltr0g. :5 fnmtuzf(y c8 e(j3zdz0vx 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 velocit7(pj*j+6 s e)tkd msbiy is 12 m/s from the north, what frequency will observers hear who abj( )eptjs +*smi7k6 dre 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 movinw4ikymnz36wj(hp 4 + bg 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 h v /+4f m6m)fovyllr2:z c(6wt3zbzbof sound is 310 m/s (a) What is the angle the shock wavffzbm :cv26lr3y +boz/h6zt vw lm( )4e makes with the direction of the airplane’s motion?    $^{\circ} $
(b) If the plane is flying at a height of 7100 m, how long after it is directly overhead will a person on the ground hear the shock wave? $\approx$    s (Round to the nearest integer)

  A space probe enters the thin atmosphere of a planet where the speete)0hj m b27led of sound is only ab2te)b lj7e 0mhout 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 the shock wave angls+y oxp0 2+kb.wb0pl ie it producesp2pb 0k .y0iblwsxo++
(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 gmz7oz20z1l oe 2-bcf$/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly overhead m (c* a b/nafw8k6v8iiand see a plane exactly 1.5 km above the ground flying faster than the speed of sound. By the time you hear the sonic a/mc*b nvaif68k(8i w boom, the plane has 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 dowkyioa3w uc qo 09grkf:-25 y5mnward from the bottom of the boat, and then detects echoes. I:k-3ow09u afry my2 kqg5co5if the maximum depth for which it is designed to work is 200 m, what is the minimum time between pulses (in fresh water)?    s

  Approximately how many octaves are there in the human audible raqi62db0 hat4rort1 8b nge? $\approx$    octaves (Round to the nearest integer)

  A science museum has a displa tnmd i1*p(dg1y called a sewer pipe symphony. It consists of many plastic pipes of various lengths, which are open on both ep*d11ng (tid mnds.
(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 u h: eu,5hxcz5- ww:g.e wa9aj3ly .tua person makes a sound close to the threshold of human hearing (0 dB). What will be the sound 5jwtuz: ee5h9u ghyaw 3,.a c:-uw .xllevel of 1000 such mosquitoes?    dB

  What is the resultant sound level when an 8n6,tu/vc (y18w gz cii*plv 4o2-dB sound and an 87-dB sound are heard simultaneou o1,*v y 6 w8v(l/ncctizigu4psly?    dB

  The sound level 12.0 m froexsr( ud,vj+lz22*x:t/ jvonm a loudspeaker, placed in the open, is 105 dB. What is the acoustic power output e2vdurs+xz /,(vox2 jn tlj: *(W) of the speaker, assuming it radiates equally in all directions?    W

  A stereo amplifier is rk2e uc 8ye99stgs6.cgated at 150 W output at 1000 Hz. The power output drops by 10 dB at 15 kHz. What is the power ouesku.2 st9 c6ecy8gg9tput in watts at 15 kHz?    dB

  Workers around jet aircraft typically wear proteczo7pcom map:su:+i;-afr8 (htive 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 distanceio:mhp+zo p(crm 8f; as7-: au of 30 m from a jet airplane engine?    W

  In audio and communications systems, the gu(-k evyan(2x ain, $\beta$ 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 tunedy;oi4n6ujb38zxu.ha lk8 2 kp 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 violin7kt/ rx22 oufz+.mnsa is 32 cm long between fixed points with a fundamental frequency of 440 Hz and a mass per unit length of txms/ zuo.r7+fkn a22$6.1 \times10^{-4 }$ 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 a jw:- f qrc3+ah+cm-mm mqb55mbove 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 q - camhcm5m-3m+5mjfr b:w+q 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 ofr :- .ojm3 her2wmx9ekarkyp)4f vn.) 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 if it is to produce resonance (in its fundame4kne32)mx 9o mr-afkj..wr e vpyh :)rntal mode) with the third harmonic in the tube?    $ \times10^{ 2}$ N

A highway overpass was observed to resonate as one full loop ;xl w4z sw3 1oekdfn./($\frac{1}{2}\lambda$) when a small earthquake shook the ground vertically at 4.0 Hz. The highway department put a support at the center of the overpass, anchoring it to the ground as shown in Fig. 12–36. What resonant frequency would you now expect for the overpass? Earthquakes rarely do significant shaking above 5 or 6 Hz. Did the modifications do any good?

  A person hears a pure tone in the 500–10yr5f/g.(cgx nvfw m7/ 00-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 r /(f5 xvmgc7.ygw/ nfthe frequency of the sound?   Hz

  Two trains emit 424-Hz whistles.hesb4 j;3rlqoq 6pho3 inm)-9 One train is stationary. The conductor on the stationary train3blo r6 -hiho;93p)j s q4meqn hears a 3.0-Hz beat frequency when the other train approaches. What is the speed of the moving train?   m/s

  The frequency of a steam train whistle as it approaches yixb,f. dmy/bbu*s 8x8ou is 538 Hz. After it passes you, its frequency is measured as 486 Hz. How fast was the train moving (assume constant velocity8.fy/db ub8s * x,mxib)?    m/s

  At a race track, you can estimate the speed of cars just by listeuuq 6ecq3+kvl ,gyew.j8 9bt1ning to the difference in pitch of the engine noise between approaching and receding cars. Suppose the sound of a certain caw9j,e1el 6k3by.u+ 8 tuqqgcvr 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 09qt+iug-cpj q1k 3pmtogether, produce a beat frequency of 11 Hz. The sho pigq u3pj0-qk+ct1m9 rter one is 2.40 m long. How long is the other?    m

Two loudspeakers arefg.:gtu;sexj.j / k r, at opposite 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 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, a.esxg.r, jkjut f :;g/t B, and (c) he hears the speakers after they have passed him, at C?

  If the velocity of blood flo3h0k0 -rlcxmmu 9 p-jsw in the aorta is normally about 0.32 m/s what beat frequency would you expect if3-mc upkhl00srjm- x9 5.50-MHz ultrasound waves were directed along 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 w.46 0avl 30t40v;b sdinr6gqci zywyspeed 6.5 m/s while the moth is flying toward the bat at speed 5 m/s The bat emits a sound wave of 6zbgtqwi6 4arsc0l wiy;dy0vn0 4v3.51.35 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 ofytr +ne ,i,8bj high frequency sound pulses as it approaches a moth. The pulses are approximately 70.0 ms apart, and each is about 3.0 ms long. How far away can the moth be detected by the bat so that the echo from one chirp returns before the next chirp isjb 8,+n,y teri emitted?    m

The “alpenhorn” (Fig. 12–38) was once used xkvawn x ;o)p f5k*7zvmoe534to send signals from one Alpine village to another. Since lower frequency sounds are less susceptible o7)kmx 5 v*px3vae ozwk5n ;4fto 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 compromised(faaxp1cky)* 6 4fa kh 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 long, 4.0 m wide, and 2.8 m high. Calculate the fundamental frequencies for the standing waves in ap(c41 fxakaf k* hy)6this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

  A dramatic demonstration, cal n;q7 ekb3/o5eymp5evled “singing rods,” involves a long, slender aluminum rod held in the hand near the rod’s midpoint. The rod is strok3;qe7vo pnby/e5ek 5med 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 threshold of hearing for the human ear at a frequeu) ( u bw43mpmjl7le5rncy of abo ujbmm3l(rpew4 75ul)ut 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 observer on the ground hears the sonic bgr brgf1 l:6doz )68d2 iabq+toom 1.l dr:6)f2gbqt oad6b1i8rz g+5 min after the plane passes directly overhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboat is 1i 4kr3y:i+ 1smmg0qw dkz6)nw5 $^{\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