What is the evidence that szfsh0v1aq*5 ib1 m2oiound travels as a wave?

What is the evidencec 89s1i3vb*axmd 7xy f that sound is a form of energy?

Children sometimes play with a homemade “telephone” by attacht ldw.2bmv:/ming a string to the bottoms of two paper cups. When the string is stretched and a child speaks into one v2:/w. tbmmld cup, the sound can be heard at the other cup (Fig. 12–29). Explain clearly how the sound wave travels from one cup to the other.

When a sound wave passes from air into water, do yo lv,3tdz(5 xtlu expect the frequency or wavelength to change?zt,5x(d 3vlt l

What evidence can yo78k4t pms-y c,k djx0t1mmb 0pu give that the speed of sound in air does not depend signifitc7mt8 mx 00k4-jp b,dmpy1kscantly on frequency?

The voice of a person who has inhaled helium sounds very high-pitched. p6hplt*eh4 y, Why?

How will the air temperature in a room affect the pitc67bl r.xh3ix v8e4t-vh 8yau th of organ pipes?

Explain how a tube might be used as a filter to reducw)vseea;,b dc)z:.fj e the amplitude of sounds in various frequency ranges. (An example is a car muffle z, a )ef.c)ds:;bvjewr.)

Why are the frets on a guitar (Fig. 12–30) spaced closer together as you p 6xv7t p 7l3vpko,ae8move up the fin vk387ox7p p ,vape6tlgerboard toward the bridge?

A noisy truck approaches you from behind a bu-soe, 1dxodc.ilding. Initially you hear it but cannot see i.xo1,do s-d cet. 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 on diffraction.]

Standing waves can be said toz27 dlwz1s 7gr; cy7gs be due to “interference in space,” whereas beats can be said to be due to “interference in time.” Explain sr1gds g 777;zwz2lcy.

In Fig. 12–16, if the frequency of the speakers were j(3 blv3 jn,jrlowered, would the points D and C (where destructive and constructive interference occur) move farther apart or closer toge,jj 3b( rvlj3nther?

Traditional methods of shgnf.sac7w/yw 5qa 4nhm990protecting 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 aremh7gfc q w.nh95/s4 ay9aw0s n 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. 3jm5h5etk9 ro(nok p 212–31. Each wave can be thought of as a superposition of two sound waves with slightly different frequencies, as in Fig. 12–18. In whicpk m952kontoer3(j 5hh 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 same direjay i9cz.mf2-zfsg4 ,ction, with the sams49azf i zfy.- ,2cgjme velocity? Explain.

If a wind is blowing, wiy 6ajrgv9( ak.5z0 zhybx4al8ll this alter the frequency of the sound heard by a person at rest with respect to the source? Is the wavelength or velocity changea g 50v.(bhxzzj96ayakr y48l d?

Figure 12–32 shows various positions of a chid9 lqa,y ;1jkcld in motion on a swing. A monitor is blowing a whistle in front of the child on the ground. At which position, A throug, 9jd1; kylcqah 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 zqzoino ((:7w8 0iv*v5vymj zlistening for the echo of her shout reflected by a cliff at the *(oi:yivz(ov7v j8zq 5w m0nz 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 below the water t qy,x-j8w:efline. He hears the echo of the sound reflected from the ocean floor directly beqf ,e xtyw8:j-low 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 ci z (e.6hkq65m5myl zat 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 scq lwiq4zol/ i/-u zb7 glv.;(vhool 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 backfirigzz/q;vuo w/ qlb. l7lv-4 (ie 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 makes when stri8nzh2e;hvi am7 : 3ndqking the water bi nd:; v83qe7h mz2hanelow is heard 3.5 s later. How high is the cliff?    m

  A person, with his ear to the ground, s qc4b7p1n-k(7ll1 rgdqxlf 9vees a huge stone strike the concrete pavement. A moment later two sounds are hbl(gq1 4lxd71ckqp n9f vlr -7eard 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 mile of distance by the “5-second 4 3vxs wczj6+prule” f3ws+v4cx6 p zjor estimating the distance from a lightning strike if the temperature is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity oce :ol52 (jk4o c+cuqmx:p1fhf 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 sound whose intensiioi, 95ppr y6oty is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a souct 4r9le3.+db*nwpu c nd level of 95 dB when fired simultaneously at a certain place, what will be the sound level if only one is exploded? [Hint: Add inr wl c d.tp49ne+c3u*btensities, not dB’s.]    dB

  A person standing a certain distance from an airplane with four equally noisy vt: i,o (jnm8 v6z5lbojet engines is experiencing a sound level bordering on pain, 120 dB. What sound level would this person experience if the captain shut down all but one engine? [,5iozmov v:t j6( lbn8Hint: Add intensities, not dB’s.]    dB

  A cassette player is said ton; y 7undou4,vtyb v1*6un9)y unzvb9 have a signal-to-noise ratio of 58 dB, whereas for a CD player it is 95 dB. What is the ratio of intensities of the signal and the background noise for each9oyvdy uunntv4 6n*)vu 17u ;,9 bbynz device? 58 dB =    $ \times10^{ 5}$ dB =    $ \times10^{9 }$

  (a) Estimate the power output of pqvcys-z3,3d8tmeeie3) 51.xnt m mhsound from a person speaking in normal conversation. Use Table 12–2. Assume the sound spreads roughly uniformly over a spherez3hqdtye.p iet e5-8 m mm13,)3vx csn 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 whos z.herseb3u7n1 zi ,;we 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 yq,1g vw0 ,lvramplifier B is rated at 40 W. (a) Estimate the sound level in decibels you wyrw1g,vv0 q ,lould 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 +-g3 d)xgkup0nyj 8 y+wr) fjtwhen placed 2.8 m in front of a loudspeaker on the sxpgyjgr k-)d8f+y3w 0u) ntj+tage.
(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. What is81q xlkmsrg6 ujfl hw(2)a/5c the ratio of the amplitudes of two sounds whose levels /5j )a wglmrf8 su26c1xlk q(hdiffer by this amount? [Hint: See Section 11–9.]$\approx$   

  If the amplitude of a sound waver6qk 5uha*7ohuim/s h n+wn-3 is tripled, (a) by what factor will the intensity increase? Increase by kn7o *-m hwu 5q/ah3sinhur+ 6a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal disdf3s tpv:5( s4xxk,(klb(fzf placement amplitudes, but one has twice the frequency of the other. What is the ratio:klzf(fs xp4fkv bd,((x 53 ts of their intensities?   

  What would be the sound level (in dB) of a sound wave in air thj5w p8ciuzm;x uk1y.1w zl b,e do(:q4at corresponds to a displacement amplitude of vibzdi (w1.5o;8 yzl:mbuqukwc, jxe1p 4rating air molecules of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level to seem a- lwwk:xf +5widzw9p:s loud as a 100-Hz tone that has a 50-dB5w d izl-xwpf:k:w9+ w sound level? (See Fig. 12–6.)    dB

What are the lowest and highest frequencies t4ff /88zm v, xgf+vktjhat an ear can detect when the sound level is 30 dB? (See Fig. 12–6.)vzmj4x,g/ 88fkf f vt+

  Your auditory system can accommodate neu(sk + ub-s/-,t pnqa huge range of sound levels. What is the ratio of highesu -p+qn(/e sus-nktb,t 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 frequencd) 1wqu5sdpc ,7b 0ijmy of 440 Hz. The length of the vibrating portion is 32 cm, and it has a mass of 0.35 g. Under what tension must m) ws5p7 1qj, bdc0iduthe string be placed?    N

  An organ pipe is 112 cm long. What are the fundamental and first three 5z+r7bl1dn0 tum 7t0ng , pkkiaudible overto7um1lt 7t d00ib r5n +k,nzkpgnes if 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 frequep*5 ,hpl :abe:obr6yl7.tka ency would you expect from blowing across the top of an empty soda bottle that is 18 cm deep, if you assumed it was a closed tubyal arl*5 . :he7b6oekppt:, be?    Hz (b) How would that change if it was one-third full of soda?   Hz

  If you were to buildyl7sx3 rwve v2,bv/f55 pi -lb a pipe organ with open-tube pipes spanning the range of human hearing (20 Hz to 20 kHz), what would be the rap y5vl,-vb 7wrl5v2/bf ie3 sxnge 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 third harmon.hb 3oyfqy/t 2 ol/5ipic. What will be its fundameyp2 /. yh/5bifoq3l otntal frequency if it is fingered at a length of only 60% of its original length?   Hz

  An unfingered guitar string is 0.73 m long and is tuned tooajuz 078w).zobm la 2 play E above middle C (330 Hzz80 lu. aozjbmwa7 o)2).
(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 len hhkw 4t 7.,agay6dc5wgth of an open organ pipe that emits middle C (262 Hz) when the temperak y4ah hdw6, tc5gw.7ature 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 azd ujy9 6rkf/fl7go+,w2gv- m t 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 Exasi3np1g6o ou +mple 12–10 should the hole be that must be uncovern 6io3g1+ uposed 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, but noadsaecra*w b, zw //t+j:xz( r,iy/k ;t at any other frequencies in between. (a) Show why this is an open or a closed pi/j*yea r,c a(xwzz;, wt: kbrsid/+a/pe. ----待选择----closedopen  (b) What is the fundamental frequency of this pipe?   Hz

  A uniform narrow tube 1.80 m lonx gzq g/g(l7zad160bi g is open at both ends. It resonates at two successive harmonics of frequencies 275 Hz and 330 Hz. What iszg0gbd1xg6/ al( 7 qzi
(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 6um.cs58 h.fpg yriw( nio +2v$^{\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 forve+8w43aujkum8 eqlsr ,1 4 lu a 2.14-m-long organ peakjs8u+381uvlw,4m elu4 rqipe at 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximately 2.5 cm long. It is open to t7+ksqp yo;d ztv6 /ij.he outside and is closed at the other end by the eardrumpqd6 y+/z vji;7s. okt. 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 bea*oc 2f.vsk80oj 0zkn zt every 2.0 s when trying to adjust two strings, one of which is 2z.ko0s n ov08zkfjc *sounding 440 Hz. How far off in frequency is the other string? ±    Hz

  What is the beat frequency if u h: n/s1h zt /ox3v/rq4x(oipw7m6fe 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 an+i au *jtfq9.g7z/2x oravhx4other (brand X) operates at an unknown frequency. If neither whistle a*/o trjz7xx.i2 fhu+4 gqv9acan be 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 beats/s tg2 f;p sj-uw/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 s-p ;uwsf/2tgjtring? Explain your reasoning.    Hz

  Two violin strings are tuned to the samuq:os+ y1v;b yj*zlo: m 6lz7ae frequency, 294 Hz. The tension in one string is then decreased by 2.0%. What will be the beat frequency heard when the two strings are played tl+qo:; *:jlmy u1s z67z bvyoaogether? [Hint: Recall Eq. 11–13.]    Hz

  How many beats will be heard if two idenfpaesj54s75.c pu8 )e+ ecfe gtical flutes each try to play middle C (262 Hz), but one is at 5.0°C and the other5.4pegp) u+ee 7eas8f5c jfs c at 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks, A, B, and C)j4*ey:a d.w,x/wly bup,e lm n-)gdu. Fork B has a frequency of 441 Hz; when A and B are sounded together, a be-bdd l) ,*.yx yjg,we a/)emuu4wpl:nat frequency of 3 Hz is heard. When B and C are sounded together, the beat frequency is 4 Hz. What are the possible frequencies of A and C? What beat frequencies are possible when A and C are sounded together?$f_A$ =    Hz or    Hz
$f_C$ =    Hz or    Hz
|$f_A$-$f_C$|    Hz or    Hz

  Two loudspeakers are 1.80 m apart. A person stands 9-)up-k b6yelc;m orud /sh2n 3.00 m from one speaker and 3.50 m from the bsk yr69 ) m-/huloe2d;nc-upother.
(a) What is the lowest frequency at which destructive interference will occur at this point? f =    Hz
(b) Calculate two other frequencies that also result in destructive interference at this point (give the next two highest). Let T = 20 $^{\circ} $C $\approx$    Hz $\approx$    Hz

  Two piano strings are supposed to be vibrating at 132 Hz, but z:3taznr7g4hwz /c:/b2k f -bklgpm8a piano tuner hears thrc4 a:/lfr27g8nkz k /htgm3bw:zp b-zee beats every 2.0 s when they are played together. (a) If one is vibrating at 132 Hz, what must be the frequency of the other ?   Hz    Hz
(b) By how much (in percent) must the tension be increased or decreased to bring them in tune?   % increase    %decrease

  A source emits sound of wavelengths:ple 9 ck.yp7g 2.64 m and 2.76 m in air. How many beats per second key9p .gc7l p:will be heard? (Assume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain fire engine’s(aag r()g*q 7gnwfcdpd.jyj9 4(+b+ wv 1obst siren is 1550 Hz when at rest. What frequency do you detect*sgwt qn1b4o+9y(bvcw 7p( ddjg)+.r (fagj a 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. um,vdtvq5, 7h What frequency do you detect if a fire engine whose siren emits at 1550 Hz moves at a speed of 32 m/s qt7udh5,mv,v
(a) toward you,    Hz
(b) away from you?   Hz

  (a) Compare the shift in frequency if a 2000- o*l mrjx5 b3vw1ki:(gHz source is moving toward you at 15 m/s versus you moving toward it at 15 m/s Arexwir(bkj3vo:g51 l m* 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. *j bq*lq,aea+ When one is at rest and the other is moving toward the f q ,*+ljqa*beairst 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 souj0c3 90lguhmjpe 8my+ fly .c)nd waves at 50.0 kHz and receives them returned from an object moving directly away from it at 25 m/s What is the received sound frequj0gu.c yy hep)jcm3m+9l 8lf0ency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed of 5 m/s As it fl dh otela(0na0rd:1 k1ies, the bat emits an ultrasonic sound wave with frequency 30.0 kHz. What frequency da ed1(t0ndhr l0oa :1koes the bat hear in the reflected wave?    $ \times10^{4}$ Hz

  In one of the original Doppler experiments, a tuba was played on ayag/ t 8o 3 ojsfs d.1th:p2qircib1*; moving flat 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 wf .s2io orsh1cb;titj81*agy d3p:/qas heard if the train car approached the station at a speed of 10 m/s ?   Hz

  A Doppler flow meter uses ultrasound waves to measure blt0y6ui 5)erjz 7x 9oysood-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 is the expected beat frequency if blood is flowing in la)i5y rz6s7yj oxt0u9e rge leg arteries at 2 cm/s directly away from the sound source?   Hz

  The Doppler effect using ultrasonic wavesjcaw0bhj0s, ( 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 frequen,huxmm* zja,-mx9+6jxtfn m 1 cy 570 Hz. When the wind velocity is 12 m/ jfj,m9 x-hxn z,xmu6m+a1t*ms from the 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 l*y9gypyh+gd*koqga n b(08)x and 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 speelur8mch 2po ,ot9f-e *i/;mjn d of sound is 310 m/s (a) What is the angle the shock wave makes with the direction of the airplaneo9-th, 8*fioe ;r 2uplmcjn/m’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 tmu f8c5s.b z-ehe thin atmosphere of a planet where the speed of sound is only abzc5mu e-fs8 b.out 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 si hln/; l9iqcb.r5t9up2k y)wave anglet/9 ps.hybu 9qr)n liikl5 2;c it produces
(a) in the air just before entering the ocean, $\approx$    (Round to the nearest integer)
(b) in the water just after entering.    $^{\circ} $
Assume T = 20 $^{\circ} $C

Show that the angle :;n- 7yy 5l2norr nczn$/theta$ a sonic boom makes with the path of a supersonic object is given by Eq. 12–5.

  You look directly overhead and see 6qnhlu qxuq6x;ssi8k d0 w5-1a plane exactly 1.5 km above the ground flying faster than the speed of sound. By the time yo;udh-xuwq 16 kqs 8s6il nx50qu hear the sonic 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 sep9e* grkw + flr7 f65t(dymd.xnds 20,000-Hz sound pulses downward from the bottom of the boat, and then detects echoes. If the maximum depth for whicgddkt.r r pw(lx6m5ff7+ye9 *h it is designed to work is 200 m, what is the minimum time between pulses (in fresh water)?    s

  Approximately how many octaves arvv ,kyv7km ndk+. 0nr3e there in the human audible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a display called a sewer pipe symphony. It h3:rire+4szd1 kqv6l consists of many plastic pipes of various lengths, which are open on bk:r4v1lh id63 zs+qreoth 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 maruz 5 4 *q24cmrut.vcbkes a sound close to the threshold of human hearing (0 dB). What will be the sound lez ct4*crubqvr .2 um54vel of 1000 such mosquitoes?    dB

  What is the resultant sound level when an) tsf+j2wuek) 82-dB sound and an 87-dB sound are heard swesf )jk+ t2u)imultaneously?    dB

  The sound level 12.0 m from a loudspeaker, placed in the open, isdt03 ig.k -wsj 105 dB. What is thk.dt0-sg w3i je acoustic power output (W) of the speaker, assuming it radiates equally in all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 Hz. The power output dux6 ut:2lo :bb n+d6yk- ;txnvo9 gf.props by 10 dB at 15 kHz. What is theyod.2n vx ; xfbt6ulgn6t-u:bpko:9+ power output in watts at 15 kHz?    dB

  Workers around jet aircraft typically wear protective devices ovemwt 42w4e:- rc( bgjggb/v/ehr 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 atb2vt ce/rwb(:4wgjh g egm/4- a distance of 30 m from a jet airplane engine?    W

  In audio and communications systems, th7pq0zy pak ai0vtf- vo8/4-x je 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 . j-lfhwbpo66tuned to a frequency 1$\frac{1}{2}$ times that of its neighbor. The four equal-length strings are to be placed under the same tension; what must be the mass per unit length of each string relative to that of the lowest string?
$f_{A}$ =    $\mu_{A}$
$f_{B}$ =    $\mu_{A}$
$f_{C}$ =    $\mu_{A}$

  The A string of a violin is 32 cm long between fixed points with a fundamental fxj442 8syk9gj1q zcnyrequency of 440gj41qsk2n y9 8yx4jzc 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 a vertical open tube filled wiz q:po nj-+d. -dab.bgth water (Fig. 12–35). The water level is allowed to drop slowly. gp.q+d.-:jao -db nzb 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 h es4 jp1:uydx0 x*wdh7e)gk/ 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 hk hs:ed07 j) 1xygdpe*u4wx/ 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 full loop 82c( jzc:dkyg($\frac{1}{2}\lambda$) 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 500–10wfn3yxeeabw;n 4*jqoisn 0c (9 fi;1.00-Hz range coming from two sources. The sound 93 e.nsai xc01 jof ;fw;i*wn(q 4ebynis loudest at points equidistant from the two sources. To determine exactly what the frequency is, the person moves about and finds that the sound level is minimal at a point 0.34 m farther from one source than the other. What is the frequency of the sound?   Hz

  Two trains emit 424-Hz whistles. One train is stationary. The conductor on the sjw35(+s. io ew,hoenhtationary train hears a 3.0-Hz beat frequency when the other train approac,i hose o35we.nh(+wjhes. What is the speed of the moving train?   m/s

  The frequency of a steam train whistle as it approaches you is 538 Hfz.rau, l0 fa)z. After it passes you, its frequency is measured as 486 Hz. How fast was the train moving (assume constantu aaf.,)zr0f l velocity)?    m/s

  At a race track, you can estimate th4r3ttpy/wup 6 ,1 2q dcxd8wase speed of cars just by listening to the difference in pitch of the engine noise between approaching and receding cars. Suppose the sound of a certain car drops by asty pca qd8/w4 ,r3ux1twp d62 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 1ko+goi 4c: mq;x 1bit11 Hz. The shorter one is 2.40 m long. How lonc qi1 mxo;g1ti +bko:4g is the other?    m

Two loudspeakers are at opposite ends of a railroad car as ij z85atqe5r3zbdg uqr:2 7b)k t moves past a stationary observer at 10 m/s as shown in Fig. 12–37. If the speakers have identicar8zbqzqk5j 5te7 ra 3gb)2d u:l 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 fl9;q-qu oz(k 6o)+iwos)n: 7q4jowh1b zf ip gtow in the aorta is normally about 0.32 m/s what beat frequency would you expect if 5.50-MHz ultrasound waves were directed along the flow and reflected from the red blood cells? Assume tqo qo4w) - k:j7i9qofzitphbus+ w6z g1n)o; (hat the waves travel with a speed of $1.54 \times10^{3 }$ m/s   $ \times10^{3 }$Hz

  A bat flies toward a moth at speek ..p h/rscwt.d 6.5 m/s while the moth is flying toward the bat at speed 5 m/s The bat emits a sound wave of 51.35 kHz. What is the frequency of the wave detected by the bat after that wave h.tck/ r..pws reflects off the moth?    kHz

  A bat emits a series of high frequency sound pulses as it approa s, emefyl6//jj ;gsd2ches 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 / j,/ ssy6d legfe;j2mdetected by the bat so that the echo from one chirp returns before the next chirp is emitted?    m

The “alpenhorn” (Fig. 12–38) was r26uy)f /6lwspde mf lp+4-usonce used to send signals from one Alpine village tlu6s/ lu-dp 4pswr )f6+2em yfo 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 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 comp(o bcehjgey:lp:z: x6r:pk20 romised 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 fez6 0hykxjg :c2: e op:p:brl(undamental frequencies for the standing waves in this room.
Length : f =   Hz
Width : f =   Hz
Height : f =   Hz

  A dramatic demonstration, called “sing m 2unpvl8n63aing rods,” involves a long, slender aluminum rod heldml3uanpvn628 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,” 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 threbckpegv3,cze-) * +c1qxf1 crshold of hearing for the human ear at a frequency of about 1000cx)3b eg* 1+cvf-1,erp cck zq 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 observesip*4eqfp ,7q r on the ground hears the sonic boom 1.5 min after the plane passes direcip* f ,epq7q4stly overhead. What is the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboat i ( wwo8/het r4 ipah3;7ufu1trs 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