What is the evidence that sw x;xt;c tom4.js /z2luv*2e yound travels as a wave?

What is the evidence that sound is a form blnio sxr ct4r77q-42of energy?

Children sometimes play with a homemade “telephone” by attaching a rw)e,08 y r+dgtmdjm c 74zqs,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. 1),jmes d 4qc8mtwg,z7d+r0ry2–29). Explain clearly how the sound wave travels from one cup to the other.

When a sound wave passes fromiuvpknzv(d0w:1qi 3jq 93 z +m air into water, do you expect the frequency or waveldqz(+zm:q31 v9wkvii0jpu 3n ength to change?

What evidence can yo05 6te jdwn f qf9qw7 f;eywizu1-n9n9u give that the speed of sound in air does not depend significantly on ff-w9q juw6nq1;n f5y90dte 7f9w ze nirequency?

The voice of a person who has inhaled helium sounds very high-pitchedfh bue,;*xm 70x e7kkg1.u rtj. Why?

How will the air temperature in abp a,-m*y5kko room affect the pitch of organ pipes?

Explain how a tube might be used as a filter to reduce t4wgvjtxy*5 )fzziz82 ib55v ew z 1e.ahe amplitude of sounds in various frequxiz) wvf45y 5b81gie*jz. 5a2vzewtzency ranges. (An example is a car muffler.)

Why are the frets on a guitar v+plyc.4 w9 yki/x: bq(Fig. 12–30) spaced closer together as you move up th il9+:kxyq4yw.pcb v/e fingerboard toward the bridge?

A noisy truck approaches you from behind a bn sx j.q7rizj 0 *gp2*k5mpnh8uilding. 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. Expla 2hgn.psj*n r*ik0 zxjm 578qpin. [Hint: See Section 11–15 on diffraction.]

Standing waves can be said to beag f1nh.)75id b oy-k1fgj.rclh l87 h due to “interference in space,” whereas beats can be said 8.).hyk a1f7gf75do-chh1lg r jniblto be due to “interference in time.” Explain.

In Fig. 12–16, if the frequency of the speakers were lowered, would , 1j vai;-hsa e1tq.aethe points D and C (where destructive and constructive interference occur) move farther ap ah1saq-1,ve ie;a.jtart or closer together?

Traditional methods of protecting the hearing of people who b;i n ug./*1gfxlgrrb,.sd3swork 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.g si31d,.b .;gn g l*srfb/xur 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; 4,g:i jrlekg thought of as a superposition of two sound waves with slightly different frequencies, as ,kjrei;: g l4gin Fig. 12–18. In which of the waves, (a) or (b), are the two component frequencies farther apart? Explain.
(12-31)
(12-18)

Is there a Doppler shift if the source and observer move in the samz 4vtuwxnp 2l y/0cij/g z+r79;)wdz1 hdoh9ee direction, with the same veo92wndluvwi/;h 4x 1 zzjptezc hry/gd)907+locity? Explain.

If a wind is blowing, will thisc/c dx s*sj*r vn6 a3uk(4go8g alter the frequency of the sound heard by a person at rest with respect to the source? Is the wavelength or velocity c3*ccx/ un8ok*g s(gdj asrv 64hanged?

Figure 12–32 shows various posnk4i 4,5puuem 9n +lxfitions of a child in motion on a swing. A monitor is blowing a whistle in front +p 49lnxn4,k m5iufu eof the child on the ground. At which position, 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 lis;cpn+wqi45 ud0p3q yptol2 * 1ti ibz;tening for the echo of her shout reflected by a cliff at the far end of the lake. She hears the echo 21q*p tpqtiilnu4w dcy2;z i o53p 0b;+.0 s after shouting. Estimate the length of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship just below the waterline. He hears the ec/6/tbtyxxaz 1w4ts +aj41s-xm xr6 pr ho of the sound reflected from the ocean floor directly below 2.5 s later. How deep is the o1jz4-x s/ r s4xa6wtrpyxm6 ta t/xb1+cean at this point? Assume the speed of sound in seawater is 1560 m/s (Table 12–1) and does not vary significantly with depth.    $ \times10^{ 3}$m

  (a) Calculate the wavelengths in air ao66 xpl- ud.txt 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 boar45tb;(neq( d z8zmzvt is drifting just above a school of tuna on a foggy day. Without warning, an engine backfire occurs on another boat 1.0 km away (Five58 d(;zmq(zbnzt r4 g. 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 ofq5ih(/rh pwh: a cliff. The splash it makes when striking the water below is heard 3.5 s h5p:(whq r/ih later. How high is the cliff?    m

  A person, with his ear to the ground, sees a huge stonem985,jy2kzo bdll3 b z9 mp/sy5-omq o strike the concrete pavement. A moment later two sou9 m5lo8y odmq,/o9z2bjbzp l3s k-5ymnds 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 12–1.$\approx$    $ \times10^{2 }$m

  Calculate the percent error made over one mi*q+1tq hk 9jfxle of distance by the “5-second rule” for estimating the distance from jk * fh+tqqx91a lightning strike if the temperature is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity ofz lt,7dk/24bu t3 yybs a sound 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 souf;v-d-99 ;r. njff8 qd ncmvo0stqv.cnd whose intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound level of 95 dB when fircw )-aurh;t bfj-(b i)ed simultaneously at a certain place, what will be the sound level if only one is exploded? [Hint: Add intensities, not dB’s.)i)h -bcb a-ujf wtr(;]    dB

  A person standing a ce w xswj vsa*l:+71txqbz3 .i2wrtain distance from an airplane with four equally noisy jet engines is expvt *i+z sx. qbs3 wwa:lx12j7weriencing a sound level bordering on pain, 120 dB. What sound level would this person experience if the captain shut down all but one engine? [Hint: Add intensities, not dB’s.]    dB

  A cassette player is said to have a signal-to-noise ratio z-.i19wi(ud 6b;.y vim x3e)oq ikupkof 58 dB, whereas for a CD player it is 95 dB. What is the ratb dzq9 kvi ei -;6k3wpuu).(iimo y.1xio 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 normal co3fmy/x1sv d93o;u gws:cu qx0nversation. Ufq9;/1d uc gomwusxsv y30: 3xse Table 12–2. 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 whose gkhk3ab5yj 5-c;k(bwxozx 4 : 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+6 rtj-w;e iwog/cp)n W, while 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 it6gwoj) e+np r;c/w- loudspeaker connected in turn to each amp.$I_{250}$ =    dB $I_{40}$ =    dB (b) Will the expensive amp sound twice as loud as the cheaper one?

  At a rock concert, a dB meter registered 130 dB when p h w8zmi;4g.qu:by dnr) zd5k9laced 2.8 m in front of a loudspeaker on the stage. dq : g);rb wh94d znmykuzi58.
(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 depd.g sh,e ro)9+d4g tbuw*i*h tect a difference in sound level of 2.0 dB. What is the ratio of the amp*d.eo4ru wb* +shg h9gi,)tdplitudes of two sounds whose levels differ by this amount? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound wave is tv4 t14f y rh9uo92jmngjci44 jdhhy98ripled, (a) by what factor will the intensity increase? Increase by a factor oft1 jdfiuh2ygn49 m4yv9jh r c4 o89j4h    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal displacement amplitudes, but one has twice the -2qib +mk *s ui5x+m di5wgen0frequency of the other. What is the qedi 0iw+un-x *+m5is 5m bk2gratio of their intensities?   

  What would be the sound level (in dB) of a sound w/:lpi )mgo zbj /x7bpt s+5lzhh7i (;cave in air that corresponds to a displacement amplitude of vibrating aimp/bblh+ho5)x7l/zsi :7 j;c(p igtzr molecules of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have w3r 9 j4vy ikreys5 m;k*zac+)xhat sound level to seem as loud as a 100-Hz tone that has a 50-dB sound levk9aiykcyxv)43smr *z erj+5; el? (See Fig. 12–6.)    dB

What are the lowest and highes;v*ey9n y u63uccezib 4c+c;et frequencies that an ear can detect when the sound level is 30 dB? (c+e zuce *; y3ucvc;9nybi46e See Fig. 12–6.)

  Your auditory system can accommodate a huge range of sous2dt(gney93/d/ciq ynd levels. What is the ratio of highest to lowest intensity dgeny29/s3t y/(d qic 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 fundameg:9am (( tzipvkd*pm5ntal frequency of 440 Hz. The length of the vibrating portion is 32i(5p*(g a 9dm :ptmvzk 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 fundame yuvjj9 i+p9b5ntal and first three audible overtones if the pipe i9pb9juy5 j+vis
(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 blowing across the tonhsu 3)mau f *4ieiezi4 +;8mvp of an empty soda bottle that is 18 cm deep, if you assumed it was a closed meivs*m43f+ e i8i uu;4)hanz tube?    Hz (b) How would that change if it was one-third full of soda?   Hz

  If you were to build a pipe organ yhf39ve o qcqjevtv, .i;6m* 1with open-tube pipes spanning the range of human hearing (20 Hz to 20 kHz), what would be the range of thv3y6tvh.*1e jfq m,vq 9ci oe;e lengths of pipes required? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

  A tight guitar string ) :jq9nyi8nszjr x0ks)m 8k6xhas a frequency of 540 Hz as its third harmonic. What will be its fundamental frequency if it is fingered at a length of only 60% ozx9y)m6 ns :qx0kjn)88ksrij f its original length?   Hz

  An unfingered guitar string is( h(fu1k5ov.s9mbnz b0p r e1g 0.73 m long and is tuned to play E above middle C (330 e.9sub p 1b5noh(kf 0rzg(mv1Hz).
(a) How far from the end of this string must the finger be placed to play A above middle C (440 Hz)?$\approx$    m
(b) What is the wavelength on the string of this 440-Hz wave? $\approx$    m
(c) What are the frequency and wavelength of the sound wave produced in air at 20°C by this fingered string?    Hz    m

  (a) Determine the length of an open organ pipe that emits middle C;nnvc-q4/n xl7h 9u2zddgs5 j (262 Hz) when the temperature is 29 sjl7n2 ;- g/4cnddxz5vunqh1 $^{\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 2w0p1hx/ se bz40 $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece of the fl3rrg20a57 t be7v yardute in Example 12–10 should the hole be that must bebeg03ryata725v rd r 7 uncovered 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, ,8zz..qiadk e and 616 Hz, but not at a , kdezai.8.qzny other frequencies in between. (a) Show why this is an open or a closed pipe. ----待选择----closedopen  (b) What is the fundamental frequency of this pipe?   Hz

  A uniform narrow tube 1.80 m long is open at both ends. It resonates at two c5i(is9ma g :zb b )laj nl(5*luyd8-tsuccessive harmonics of frequencies 275 Hz and 330: (c8smal z( g yiuba-5*)t jb59inldl 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 bu;mzx,mz6 r,d(:kdv :,-ddt eo 9 fj63nnihr $^{\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 with 6,ms/b jm0cnw2 bc(kaze2b/hin the audible range for a 2.14-m-long organ pip,(2m/abbwsc/k2nh ce0 jb6mze at 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximately 2.5 cmhbbtu,xvm63 2 long. It is open to the outside and is closed at the other end by the eardrum. Estibvbhm ut,x 623mate the frequencies (in the audible range) of the standing waves in the ear canal. What is the relationship of your answer to the information in the graph of Fig. 12–6? $f_1$ =    Hz $f_3$ =    Hz $f_5$ =    Hz

  A piano tuner hears one beat every 2.0 s when trying to adjust tuvd q-+f a .4lz0r3wd ztvlx3lk- -xf3wo strings, one of- -avx-r lwv.04kxq u+ 3fzdlfz3l3dt which is sounding 440 Hz. How far off in frequency is the other string? ±    Hz

  What is the beat frequency9k f: / )kkgubdpw956kf tnne: ,s,oqy 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 operates at 23.5 kHz,t,okvsoj-l7(ub :- ng while another (brand X) operates at an unknown frequency. If neither whistle can be heard by humans when played separately, ( b on-,vso-l:jt7uk gbut 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 be9,zca/5 vbh1r53q ymxyo4x caats/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 stz4,yx ba1vo9ry 5/m5chcqx 3aring? Explain your reasoning.    Hz

  Two violin strings are tuned to the sa)c 27msewcs js(x)+pg ,7ixjx :4 dfykroaw62me frequency, 294 Hz. The tension in one string is then decreased by 2.0%. What will be the (+poj sgdr i7jxaxw):,cf4cew s )2s ymkx672beat frequency heard when the two strings are played together? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be hea,3me;p fb(i17 blrruo rd if two identical flutes each try to play middle C (262 Hz), but one is at 5.0°C and the other aomb ,(b37;ri1 lreufp t 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning fosdw2uijs 7: i1rks, A, B, and C. Fork B has a frequency 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 beat s ui s17di:jw2frequency is 4 Hz. What are the possible frequencies of A and C? What beat frequencies are possible when A and C are sounded together?$f_A$ =    Hz or    Hz
$f_C$ =    Hz or    Hz
|$f_A$-$f_C$|    Hz or    Hz

  Two loudspeakers are 1.80 m apart. A person stands 3.00 m from one speaker ado 0ow1dvd,- .)c; rz rup2sofnd 3.50 m from th.crod2-duzp o;drfwo 0)v1 s,e 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 vibra16c+ncadxrj( ting at 132 Hz, but a piano tuner hears three c(cd+ raxn j61beats 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 wavelengths un uu2e 90tubn9:w o+n2.64 m and 2.76 m in air. How many beats per second will be heard? (As0:wuu e+un 2o9u9bntnsume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain fire engine’s sirvk/3pcoggp;r nf o2;w 8 i/2hoen is 1550 Hz when at rest. Wkwnoc2of2i h //r;;ovgp 8g 3phat frequency 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 whosuh ldx ci8i3nau9:/. ul q,h2ke siren emits atlqh: u a2ni3l./xhic u8d ,9uk 1550 Hz moves at a speed of 32 m/s
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift in frequency if a 2000-Hz source is moving toward you at tck9uj7j6chbooh5ki:+ k9t fgqd64/ 15 m/s versus you moving towar:ku476jdkooi h6c5gtbt j9+/h9k cqfd 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. When oneam5 aux g (xs/:ie5a5u is at rest and the other is moving toward the first at 15 m/s the driver5g as/5e5u mi:xuxa (a 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 ( pu yhcqj8;+kultrasonic sound waves at 50.0 kHz and receives them returned from an object moving directly away from it at 25 m/s What is the recjy +q(h8ku;cpeived sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed of 5 m/s As it flmimi 6te)2me7 ies, the bat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency does the bat hear in the refl26tm)meemi 7i ected wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experiments, a tlqz ez387 x2cne(0iz5q 5cjhu uba was played on a moving flat train car at a frequency of 75 Hz, aq( z c3hz570ujcnqlz8e xe5i2nd 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 waves /u(7 lq l9nayfto measure blood-flow speeds. Suppose the device emits sound at 3.5 MHz, and the speed of sound in human tissue is taken to be 1540 m/s What isyua(9nql l f7/ 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 waves qtbaig3tv1oqx86 sd ubq*5+13b cl7gqd 5sk .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 xx yq r,bgv; t gq-htjl698eb7+4mb 3xsound of frequency 570 Hz. When the wind velocity is 12 m/s from the north, what frequency will observers hear hx x tbgqg,q9br7vl + b6e8yt3;4 m-xjwho are located, at rest,
(a) due north,   Hz
(b) due south,   Hz
(c) due east,    Hz
(d) due west, of the whistle? What frequency is heard by a cyclist heading    Hz
(e) north    Hz
(f) west, toward the whistle at 15 m/s?   Hz
Assume T = 20 $^{\circ} $C

  How fast is an object moving oovt yl*(g3 8lssm8t/.zx khw 9n 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 6x9gg*s+nvxbh /bbcw vf7o ),sound is 310 m/s (a) What is the angle the shock wave makes withx+svn 7cf)xo6/g b , gvw9*bhb 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 pla02okn*x q5 kohnet where the speed of sound is only about 3okh0 ko 2*qn5x5 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} $