What is the evidence that sound travels as a wavepz6 9lpn0lt/ cdui-.7p0wbjh ?

What is the evidence that sound is a form of1-bdhkr8bw xv .hg2sm 03*gaecjkrbt (gg-9, energy?

Children sometimes playrdi.dme+i4cs+.jkz , j yzg+uh3d k9/ 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 dky+ch..d zdiezm3k+u+ /rgj 4si9 j,other cup (Fig. 12–29). Explain clearly how the sound wave travels from one cup to the other.

When a sound wave passes from ad q8o)ke6nex (ir into water, do you expect the frequency or waveleng (6e qko)exdn8th to change?

What evidence can you give that the speed of sound in air does not y,bx 1t8 or2h0hoxjbk1 , o5qtdepend significantly on frequenkrt ho,xt02o 18,yoxhq5bj1 bcy?

The voice of a person whoec2 a6byzr9li n:q j 1r:lzjo:z37wa9 has inhaled helium sounds very high-pitched. Why?

How will the air temperature in a room a uw 8bqfeb8 l.dbff59-qtmuve/gv ;j5;(:bt bffect the pitch of organ pipes?

Explain how a tube might be used as a filter ) :79,xxvuvsp,;1hvt nqupqpto reduce the amplitude of sounds in various n pv)x1v p7 xqu9qpvu,:;hs,tfrequency ranges. (An example is a car muffler.)

Why are the frets on a guitar (Fig. 12–30) spaced closer together as you move ux9u -q+okcbz z*-rn8 ap the fingerboard toward the r -n zc*ukxz-q9b+ o8abridge?

A noisy truck approaches youo5ydx 5ola94vxq (y w- from behind a building. 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 Seyx-oy (9a554dqv oxlwction 11–15 on diffraction.]

Standing waves can be said to be due to “interferencez w6/*3hk0z :lsehm;yjiax (85 ax lzg in space,” whereas beats can be said to be due to “interference in time.” Explai lx:g(xwa6ys03 ez8zji/z ; m h5kal*hn.

In Fig. 12–16, if the frezr59 (vf (.l2aqwy klfue (hurw0k+a 0quency of the speakers were lowered, would the points D and C (where destructive and constructive interference occur) move farther apart or2ly0l.far +quhu(wvf(0z wr9(kkea5 closer together?

Traditional methods of protectingffkigiu ,x4(:l ei58 d 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 electronic 8 :x4(l5kfdiu, ieigfally, 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 beg. //pbur6p)aey8b f w thought of as a superposition of two sound waves with slightly different frequencies, as in F6 e/yg uppb8rf)./awbig. 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 *jk1zcjdp x , ,j0tqa+source and observer move in the same direction, with the same ,*cqt akj,j1d+px0j z velocity? Explain.

If a wind is blowing, will this alter tv0 6+fiomj5 /mfc qgd 6bms5j+he frequency of the sound heard by a person at rest with respect to the source? Is tqs 5djcf/i6b5 0 +mgmvjf6 m+ohe wavelength or velocity changed?

Figure 12–32 shows various positions of a child y n2ysvfj.i5zfp ocm.b7 y6.( 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 child hear the highest fpf(zy 5mj6c2y7.nf vbo..i ys requency for the sound of the whistle? Explain your reasoning.

  A hiker determines the length of a lake by 9w5q wn2a.p ta xjb1h2listening for the echo of her shout reflected by a clifa5 1hpnwxbq2j9a2 wt. f at the far end of the lake. She hears the echo 2.0 s after shouting. Estimate the length of the lake. $\approx$    $ \times10^{ 2}$m

  A sailor strikes the side of his ship just/,gnb v7ochsu korso, .-p i0( below the waterline. He hears the echkr(v./o0sg7-osu c,i ph , nobo 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 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 ;;wjeks kl lu wr7pv/k lhw4:3:pb/ 1pat 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 ju0qbz) ad1j6g lst above a school of tuna on 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)bl azq06jg)1d by the fish,    s (b) by the fishermen?    s

  A stone is dropped from the top of a clv32a 8m ys6ukriff. The splash it makes when striking the water8sumr3a 2 y6kv below is heard 3.5 s later. How high is the cliff?    m

  A person, with his ear to the ground, seesfxo+r.ui2nmo (g j/g: 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 thur :oggj.o2n+imf / x(e impact occur? See Table 12–1.$\approx$    $ \times10^{2 }$m

  Calculate the percent error made over one mile of distance by the “5-second rf 3j j,e+pm:suule” for estimating the distance from a lightning strike if the tempfum3 +,e :jspjerature is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity o m;ad7 2pzic5f5,7 n he9ayihaf 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 soun;+i8qgc6zm vj.d l1djd whose intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound levew *bbk bhnuopv8*+ +/gl of 95 dB when fired simultaneously at a certain place, what will be the sound level if only one is exploded? [Hint: Add intensities, not pg kw hb/ob+v+nub*8*dB’s.]    dB

  A person standing a certain distance from an airpl ofzxaf -c)3m) 1 yt0x5)ne pin6hcv4tane with four equally noisy jet engines is experiencing a sound o fmi)z6x0 xf3v5n)e 4)h1cyn ptc-talevel 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 of 58 dB,.hxkwya tlf td1(7lwi/5 n-2 q whereas for a CD player it is 95 dB. What is the ratio of intensities of the signal ank5qllf (wd attxy- 7iw2 h1/.nd 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 conve5pvkwo k4vm,)rsation. Use Table 12–2. Assume the sound spreads roughly uniformly over a sphere cente)k mwkvp45v, ored 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 whvellyj1 xt3 z:++3wma n2l8bcose 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 250gs8jb7 :eel6 y W, while the more modest amplifier B is rated at 40 W. (a) Estimate the sound level ilj6sy78eeb g: n decibels you would expect at a point 3.5 m from a loudspeaker connected in turn to each amp.$I_{250}$ =    dB $I_{40}$ =    dB (b) Will the expensive amp sound twice as loud as the cheaper one?

  At a rock concert, a dB meter registered 130 dB when place20-vei.e e)l :ptg. t vbk y8xi7+vvjad 2.8 m in front of a loudspeaker onk. yvi2 e tt x0v7v)ev+:.a-pg8blej i 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 of 2.0 dB. Wyz o* 5tp+vok)z5y -.sxyrnb5hat is the ratio of the amplitu+r5oko )* 5yvzynby.- t szx5pdes of two sounds whose levels differ by this amount? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound wave is tripled, (a(-6 s+ghczw 9ib*at:qw )j8ed v0qzcx) by what factor will the intensity increase? Increase by aq6qg w+8-j:whv )z9idzeac *stc 0(xb factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal displacement amplitude/er0(h)c clv rs, but one has twice the frequencv(clrce rh/0) y of the other. What is the ratio of their intensities?   

  What would be the sou.kotqh;hiy lmu 8fa :c99bn1 z+re41qnd level (in dB) of a sound wave in air that corresponds to a displacement ampl:+h h qr18b9 . ;fo ylazu19tmeqci4nkitude of vibrating air molecules of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level to seem3nro ;ci4wz 5 nv-,psr as loud as a 100-Hz tone that has a 50-dB sound ; -n4ziscnr3vp ,o5rw level? (See Fig. 12–6.)    dB

What are the lowest and a,z (np cv7yz.:q 5wtkkz0mk7 highest frequencies that an ear can detect when the sound level is 30 dB? (See Fig. 12–6.),kzkcm 7vp.ak7 z nz05t qy:(w

  Your auditory system can azs; efvcuxhf+3 *k*6nky y5.accommodate a huge range of sound levels. What is the ratio of highest t cek* 5akfhyy36;f+suz*xn v.o 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 frequency of 440 Hz. The length of *0d nit9; 9fevkn j:8;qmhdo stheho;vdt:0qn m8 i;f d*nsj9e9k 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 c /0 twu2sq3ga7g1qxqb,2r,w(p qycblm long. What are the fundamental and first three audible overtones if the 0/, (xbq uwl 1qq3bt2sqga,7 rypc2gw 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 expect from blowing across the top of an n,xvrwm - veyp+i8 8)zempty soda bottle that is 18 cm deep, if y-x+ n w8)pzvm8, erviyou 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 spa00dhmx 2y +l1 fu*hkxhnning the range of human hearing (20 Hz to 20 kHhdfu*01mk xy+ x 02lhhz), 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 frequenu z2/0la ldg6xc5)b(1c ov plgl,vj5jcy of 540 Hz as its third harmonic. What will be its fundamental frequency if it is fingered at a length of only 60% of its orl v vd2 05zopgl(jacx,jgb5lcl16/u )iginal length?   Hz

  An unfingered guitar string is 0.73 m long and is tuned ) j w*0nsk+ ctxp( g,eauz3wa9to play E above middle C (330n z+ 3e9kwtg ap (uswj),c*xa0 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 open organi;.ym t5ynt ;hy3s m9ay9if7o pipe that emits middle C (262 Hz) when7nt9ytmm3 9i o5hy; sy.iaf;y the temperature 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 imo8os j-7gc 8at 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 1 cur31lvm1nkExample 12–10 should the hole be that must be uncovered to play D above middle C at 294 H 11ucr 31klnvmz?    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 r)s+pp**lf;d* chj e jdesonate at 264 Hz, 440 Hz, and 616 Hz, but not at any other frequencies in between.p sec;+ d*ld j**p)fhj (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 jayc:pp q8+xo - yot58ntla:)both ends. It resonates at two successive harmonics of frequenciqltt8c)aanxp5p:y o :-o y8+j es 275 Hz and 330 Hz. What is
(a) the fundamental frequency,    Hz
(b) the speed of sound in the gas in the tube?$\approx$    $ \times10^{2 }$ m/s

  A pipe in air at 20 ac:j,*4k1oww. cuw(rqju i e.$^{\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 organ 61fqpg5 xa7ak3:ld op odc)cq8)0 pjgpipao cq67p:qopjp5c013 kgd 8flgxd a))e at 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximal:o dtfi6e/ 5mgmj0 9otely 2.5 cm 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 relljd59/t:gm o e 0mf6oiationship 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 at9an+7qrom 1r d.2ci wdjust two strings, one of which is sounding 4407ciawmr+t 1 .odq9nr2 Hz. How far off in frequency is the other string? ±    Hz

  What is the beat frena3qtfxqr oh lq4:x4b2 p9f +*quency 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, while another (brand X) oxl 4deh8x r 36hu wswn1p(,rm8perates 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 sm nrh6 uhr,pxdwl3ex (s 481w8imultaneously, estimate the operating frequency of brand X.    kHz

  A guitar string produces 4 beats/s when sounded with a 350-Hz tuning foh;3w3-s9 yicd9vi oh)m,6a4luxdr +s 7igqsn rk and 9 beats/s when sounded with a 355-Hz tuning fork. What is w4v has;lis-)s7uy9c q i,rndgihm9 33+x6 dothe vibrational frequency of the string? Explain your reasoning.    Hz

  Two violin strings ar+(j/c* f,j ,g2lkcm by2giq dye tuned to the same frequency, 294 Hz. The tension in one string is then decreased by 2.0%. What will be the beat frequency heard when thb,j2/l(gc2+gy m c kjqydfi*, e two strings are played together? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be heard if two identical flutes each trbtzrpi .4 c-bnotzdg/4 3e+azw; 6:g cy to play middle C (262 Hz), but o4otb3t/.e gbia+z rp;-z 6 cd:zcwgn4ne 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 frequency of 44fmiw0m6m-y)q9 3gice9 z fih) 1 Hz; when A and B are sounded together, a beat frequency of 3 Hz is heard. Wymh9mi-ec )f 0) 39gfm6iwqzi hen B and C are sounded together, the beat frequency is 4 Hz. What are the possible frequencies of A and C? What beat frequencies are possible when A and C are sounded together?$f_A$ =    Hz or    Hz
$f_C$ =    Hz or    Hz
|$f_A$-$f_C$|    Hz or    Hz

  Two loudspeakers are 1.80 m apart. A person stands 3.00 m upy0sop+5(y5frv-o(4q q crs from one speaker and 3.50 m from the oc +qu-rysq o((55ryf4vps p 0other.
(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 oj e. l+xnmsj qrx:3/x4qai ,;vibrating at 132 Hz, but a piano tuner hears three beats e i+x .nj:qxx; 3eqojrm/al ,4svery 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 2.64 m and 2.76 m in air. hiuror3- 1p.rp02h fmHow many beats per second will be heard? (Assmpu r hih1fpror2-30.ume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant freq3dzrydi8t1w7 uency of a certain fire engine’s siren is 1550 Hz when at rest. What frequency do you detect if you move witdi7 d18yrtw z3h 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 engw- d)+a29ohjw 6jtd+qdrki 4oine whose siren emits at 1554ddioh92 r+-aq)+wt djjkw 6o0 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 movinmzv0livv9 5 8sg toward you at 15 m/s versus you moving toward it at 15 mmv vi05s98lv z/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 one i0,f ti+4lgd mdb+w-b e)wr hm5s at rest and the other is moving toward the first at 15 m/s the drhdib0,b lder-wwm54 m + fgt)+iver 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 a6wpb7i9-c glb ei x;+kt 50.0 kHz and receives them returned fl7k6w cpeg-bi +bi 9;xrom 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 atmzwgycyj10 r33 b4ax4 a speed of 5 m/s As it flies, the bat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency doe z4caby1mrgx3 j43y0ws the bat hear in the reflected wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experiments, a tuba was playeiv20oi3iq8z, qf nhn*8 6gqu6yaagp ;d on a moving flat train car at a frequency of 75 Hz;gq0niofqv23 6 *qi,a ynh ig8 z86apu, 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 waves to mig)g;h2 +zuut3c rann 5+s0mseasure 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 Whatrg2asg);5czn0i +muts nh3 +u 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 ultraso,(gbk i8o;ynd nic 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 veli+ywvspz 1nh/y *3 4(ysnuv7s ocity is 12 m/s from ny (sv73i vwy /zpn*1+4 shyusthe 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 moving on land if its speni nnyy06hm k4i8g d(5ed 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 xgi14ipwzuq p7o m*(5 m/s (a) What is the angle the shock wave makes with the direction of thow47 1 x(piqpm*iz5ug e 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 they/q6lfnpv, 7v3-yhi qac8t/ q speed of sound is v,/- pa7v tlcqhfq8/nq63yiyonly 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 8)rf nc*e/whtn p5 sj8ew4j)v3v3+v gko5wiu;500 m/s strikes the ocean. Determine the shock wave angle it produn vi4fp3g 8+ / che;k5o3svtej5u*rj w)v)nwwces
(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 bw ht/f qn5/ppbni)*/ /rtacu.:nx 6k$/theta$ 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. cf7sumgx9 .e4tvr: y65 km above the ground flying faster than the speed of sound. By the time you hear the sonic boom, the plane has traveled a hor6 tf9.c xegmv:s7ry4 uizontal 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 s z(ti7 -4aoh.gnteyi u z999dqpi:gzrn um) .*ends 20,000-Hz sound pulses downward from the bottom of the boat, and then detects echoes. If the maximum dept:q7 -4nr. udph)9tntg.o9* yegaiz ziiu z(9mh for which it is designed to work is 200 m, what is the minimum time between pulses (in fresh water)?    s

  Approximately how many mv :o*d( h;sacoctaves are there in the human audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display calledd dwru*p.-9gn a sewer pipe symphony. It consists of many plastic9w. n*d-gdrpu 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 close to the threshold10*jfroevm *d1yz sujj9 /9o x of human hearing (0 dB). What will be the sou vfjsd1j*om1uje/ zr0o9*x9y nd level of 1000 such mosquitoes?    dB

  What is the resultant sound level when an 82-dB sound and an 851;qoi 8 b6pm,m mpjxl7-dB sound are heard simultaneousl8 i ,blqx5op16;mjp mmy?    dB

  The sound level 12.0 m from a loudsz v6)mgpio+ ;aht+bm ) it9ym(peaker, placed in the open, is 105 dB. What is the acoustic power output (W) of the sp+zm69m(tb g)t maiv );hpy+oi eaker, assuming it radiates equally in all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 Hz.l vwnhh6 93:af The power output drops by 10 dB at 15 kHz. 9 h :vhfaw36nlWhat is the power output in watts at 15 kHz?    dB

  Workers around jet aircraft typically wear pro vb+5e0uptjul u;0.sltective devices over their ears. Assume that the sound level of a jet airplane engine, at a distance of 30 m, is 140 dB, a e5vul0 pbusu+l;.j0tnd that the average human ear has an effective radius of 2.0 cm. What would be the power intercepted by an unprotected ear at a distance of 30 m from a jet airplane engine?    W

  In audio and communications systems, th2v 1cwzhbgt,*os 4xe7 e 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 a fre tl,2*;dqjjdz quency 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 is 32 cm long between fixed poin5iv0 wrqo d vvihx)f2k7 9i5af,0h4fh5elye9ts with a fundamental frequency of f5 0 4lvi9qr2if,d0fva e57o) hwik5xh9veyh 440 Hz and a mass per 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 into vibration above ars xorn 91qi2zk, +fhi o235:g, mgsxz vertical open tube filled with water (Fig. 12–35). The water level5g ,2nqfxso1g9rzs3xmi r:i+ ,k2hoz 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 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 tube that6h6i2mis43*oupoxsi t +1h zx h6d m6t is open at one end and also 75 cm long. How much tension should be in the string if it is t*spu2 63tiho+66hx 6soi mzhi 1mdxt4o 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 full b8qcjrtab)*3p20 t e aloop ($\frac{1}{2}\lambda$) 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 ih2 .5u2 u*g s4lvurbli qo8ov*n the 500–1000-Hz range coming from two sources. The sound is loudest at points equidistant from the two sources. To determine exactsvh bqv22ug4ru8 i o5*o.*lully what the frequency is, the person moves about and finds that the sound level is minimal at a point 0.34 m farther from one source than the other. What is the frequency of the sound?   Hz

  Two trains emit 424-Hz whistles. One train is stationary. The conductor ojtp gw a-m-v08bad.nbe- g9(clh6r0e n the stationary train hears a 3.0-Hz beat frequency when the other train approach gh b(-jr-amwaebdpn0lg9 .0c vte6-8es. What is the speed of the moving train?   m/s

  The frequency of a steam train whistle as it approaches you is 50(blq i*f00 an)nuu.org0 s+b4qkoo u38 Hz. After it passes you, its frequency is measured as 486 Hz. How fast was t4kbunooalo q(g )i ur0un+ s *b0fq.00he train moving (assume constant velocity)?    m/s

  At a race track, you can estimate the speed of cars just by list dhj 5lo/psje; d3st,6e il-0pening to the difference in pitch of the engine noise between approaching and receding cars. Suppose the sound of a certain car drops bipl/ep 5l , jdo-3;jh 6edts0sy 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, nhf1vpxa84 0uproduce a beat frequency of 11 Hz. The shorter one is 2.40 m long. How long is the other?pna vxfhu 4081    m

Two loudspeakers are at opposito h6 waj+j4rkqs ;;n, kia.n6we 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 +6qswnk6 jnh r;,awk;a .oj i4frequency 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 tn1kv y;ar+6e9 y(y kclhe 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 and reflected from the red blood cells? A ce yn(av 6k+91kyyrl;ssume 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 flyie5z7;vt xt- )lg)th*tn6ygyzng toward the bat at speed 5 m/s The bat emits a sound wave of 51.35 kHz. What is the frequnyt-;75)v* etx)lyz hzg gt6tency 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 ap /u gs(5u0uz+mh,aw m9 b2 wibyjxl)d4proaches a moth. The pulses are approximately 70.0 ms apart, and each is about 3.0 ms long. How far away can the m9 ma5 )u4j0,+sb (dh2uwy /xmilgzuw both 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 9i l bq. tzxy7b4ot9 v;ei9s*zonce used to send signals from one Alpine village to another. Since lower frequency sounds are less susceptible to intensity loss, long horns were used to create deep sounds. When played as a musical instrument, the alpenhorn must be blown in such a way that only one of the overtones is resonatb xv*t4io. i9zqyeb;979tslzing. 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 comprom;li re9-rqqx956vyq; y/hx sk ised by the presence of standing waves, which can cause acoustic “dead spots” at the locatik9hxlqq- vrrse;x; 6y9qi5 y/ ons of the pressure nodes. Consider a living room 5.0 m long, 4.0 m wide, and 2.8 m high. Calculate the fundamental frequencies for the standing waves in this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

  A dramatic demonstration, called “sim73:i;yjbts onging rods,” involves a long, slender aluminum rod held in the hand near the rod’s midpoint. The rod is stroked with the other hand. With a little practice, the rod can be made to “sing,” :yst37ob mj;i 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 thresholdevw/ i 5pt*ko6;:mef v of hearing for the human ear at a frequency of abou;i/ efe o5:*w vmvpt6kt 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 the1qn3wldi h.0 wkqz;c( ground hears the sonic boom 1.5 min n(k.1l;d w3 qhzq 0cwiafter the plane passes directly overhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboat(m3 -vowgoad 7 is 15 $^{\circ} $ in a lake where the speed of the water wave is 2.2 km/h What is the speed of the boat?    km/h