What is the evidence that sound travels) udp-3c bmsc9 as a wave?

What is the evidence that yyn d h37lru*6sound is a form of energy?

Children sometimes play with a homemade “telephone” by attaching a strinw a23 9cowcuqv o4sq2/g to the bottoms of two paper cups. When the string is stretched and a child speaks into one cup, the soq4 2qaowuw3c/s cv29 ound 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 you ofd *pbj955sh y9nre( expect the frequency or wavelength to c*( 5 yob9r 9pnfhjse5dhange?

What evidence can yo h gyte/36c*4nhu7nth u give that the speed of sound in air does not depend significantly on freqynt6 hh *h3en 4tguc/7uency?

The voice of a person who has inhaled heliumy8smx bj4p q+g.ajz4a+sy 7.s sounds very high-pitched. Why?

How will the air temperature in a room affect tejc;03oj1wh pobh- k/he pitch of organ pipes?

Explain how a tube might be used as a filter to reducct3pm1p3z l) e3;mm+nhumyzh4 gbq) 8k2 y/yoe the amplitude of sounds in varioucpyem38z) 3pghtq 2 lmn1mm)4bo3+ku h;/ yzys frequency ranges. (An example is a car muffler.)

Why are the frets on a guitar (Fig. 12–30) spaced closer together as y2(7fy wgp5sxg/x9f; 47xi p fvu*g g4q .txzqfou move up the fingerboard toward the vgf4psu5zf 7/(p9 gf27fx xg.*;4 wgxq qityxbridge?

A noisy truck approaches you from behind a building. Initially you hear i*br5*kx: xxk xd 5wnw/t but cannot see it. When it emerges and you do see it, its sound is suddenly “brighter” — you hear more of the hi wx*br5/* dx:kkw5xxn gh-frequency noise. Explain. [Hint: See Section 11–15 on diffraction.]

Standing waves can be said to be due to “interference in sp c75q0jjqupc 5 8ax-aje.g:vvace,” whereas beats ca jj7 ccvqx jag58:5uvpa -0.eqn be said to be due to “interference in time.” Explain.

In Fig. 12–16, if the frequency of the sa4bema)4 v/9nn klb vg/5dlz 3/0dnjtpeakers were lowered, would the points D and C (wherd4 5zk4/vl n mtn93 b0)bj nvd/aleg/ae destructive and constructive interference occur) move farther apart or closer together?

Traditional methods of protecting the hearing of people who work in areasc8h1bsbtup ( 2pps5z) 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 bloct)p hu1 p5bp(bcz8ss2k the ambient noise. Instead, a device is used which detects the noise, inverts it electronically, then feeds it to the headphones in addition to the ambient noise. How could adding more noise reduce the sound levels reaching the ears?

Consider the two waves shown in Fig. 12–31. Each wave can beh0;(ae fe*z.bb9a oi g6/z5fv5mnh ay thought of as a superposition of two soabzi.h 6vymgba* h;5eaz90/e( nff5ound 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? Explain.
(12-31)
(12-18)

Is there a Doppler shift if the source and obserdkj b *ufxqrd 3(0py;m/je ;*rver move in the same direction, with the same velocity? Explai * ux0;b/q rdpk(f*d3ejj;ym rn.

If a wind is blowing, will this alter the frequep1+t 7x 2qz-hf wl3w-w kgtsf(*m26s engvw t;ncy of the sound heard by a person at rest with respect to the source? Is ws-w kwt vnf; 61z2-*g+stf7 l t3w2xh q(gpmethe wavelength or velocity changed?

Figure 12–32 shows various positions ox)dil.;u6y 7oi5v j iff a child in motion on a swing. A monitor is blowing a whistle in front of the chiox5v)iju67li .; dfiy ld 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 listening for the ey yz/u9;c- zp cta773jd(weo lcho of her shout reflepjwz(c7zc l-yy9o/ ;u3ae7t d cted by a cliff 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 below the waterline. He x, ogd-11 dpxie unne9758 jdgpwl l976zrw/phears the echo of the sound reflected from the ocean flu w xpldp1,pn5/ ei89 g6-1nd9xe j7oz w7glrdoor 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 at 7jc- ytam;7eghe ko*(20 $^{\circ} $ C for sounds in the maximum range of human hearing, 20 Hz to 20,000 Hz. $\lambda_{20Hz}$ =    m $\lambda_{20kHz}$ =    $ \times10^{-2 }$ m(b) What is the wavelength of a 10-MHz ultrasonic wave?    $ \times10^{ -5}$m

  An ocean fishing boat is drifting just above a school of tuna on a foggy day.-zjkc f0 xzn07+pgrg0 wc4rb: 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) by th z-+:0fr7pc4cg gbj znrx00wke fish,    s (b) by the fishermen?    s

  A stone is dropped from the top of ascv5c3z*vwpo.xgfeb)9ahn j: 4 d (q6d0a7tf cliff. The splash it makes when striking the water bepwh cn: ob4vvg d79zcf3ejq.5af axs6t(d*0) low is heard 3.5 s later. How high is the cliff?    m

  A person, with his ear to the ground, sees a huge stone 1c z:c8b4t:oyx: hgy/ rz fxfsh z30j2strike the concrete pavement fx/ 3 :yzgxo2yj:0ctr4s h fhzb8z:1c. 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 the impact occur? See Table 12–1.$\approx$    $ \times10^{2 }$m

  Calculate the percent error made over one ml6 cg:m4f-+ jmu/yuyo ile of distance by the “5-second rule” for estimating the distance fm6m uyug-ly+ofj c:4/rom a lightning strike if the temperature is (a) 30 $^{\circ} $ C, $\approx$    % (b) 10 $^{\circ} $ C$\approx$    %.

  What is the intensity of a sound at the pain level of 12,e4qpw7)p vx73ujwflw9 cx( m0 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 whb ;m bs79 qrxod,pz/4;8nepbtose intensity is $2 \times10^{ -6}W/m^2$?    dB

  If two firecrackers produce a sound level of 95 dB when fired sx61q,q,/k:f hg stkxsimultaneously at a certain place, what will be the sound level if only one is exploded? [Hint: Add intensit ,6qgxsq:f,1tkxhsk / ies, not dB’s.]    dB

  A person standing a certain distance from an airplane with four equallydwab.dv rtyai*67 /7kbswk: / noisy jet 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? [Hint: 7/.ayta: brvsk dk* 76iw/bwd Add intensities, not dB’s.]    dB

  A cassette player is said to have a signal-to-noise ratio of 58 dB, where3h7jk. e3 fnvdmnmu8uwh rie g(8 ::c:as for a CD player it is 95 dB. What is the ratio of intensities on7ehd3rm:w8e ugm::.jc3( uv8 ihfkn f 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 tyti-cbtwez, * ()e/nnormal conversation.t y,t * tn/czie(b)e-w Use 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 ear8u)ouv b:u5wbdrum whose 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 252 jto7w/oiqk/0 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 loudspe/7wj o2qk/ iotaker 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 d2.jmevb8 t:zdB when placed 2.8 m in front of a loudspeat bz.e: dvj8m2ker on 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 .asi m*8 lup 71wj(qgalevel of 2.0 dB. What is the ratio of the amplitudes of two sounds whose levels differ by this amount? [Hint: See Section 11–9 qwjs7pl (.ag* m8ia1u.]$\approx$   

  If the amplitude of a sound wave is tripled, (a) by what factor will the intea:f gb5e z6 ru*bf a,z9ys e((++huxvfnsity incr*bz(+ h,gsuf+u9afa xf:6bzv 5yer e(ease? Increase by a factor of    (b) By how many dB will the sound level increase?    dB

  Two sound waves have equal displacement amtwlte9chwzi l6,k b72jf kv:5./d ;fyplitudes, but one has twice the frequency of the other. What is the ra ktl y .zdiw6wk5 eht/vbf9:j, l7f2c;tio of their intensities?   

  What would be the sound level (in dB) of a sound wave )u ra gtpv73z2aj)9zcin air that corresponds to a displacement amplitude ov j2uraaz)g9)cz 3t7p f vibrating air molecules of 0.13 mm at 300 Hz?    dB

  A 6000-Hz tone must have what sound level to seem as loud as a 100-Hz tone thsw18jy rh:w cm:6uxz:ycg-xi*3 m3 jwat has a 50-dB s1 zh3 yj:s6mygww:uxi:xwc rj8c -3*mound level? (See Fig. 12–6.)    dB

What are the lowest and highestovq bz y:rddq +0a/9t. frequencies that an ear can detect when the sound level is.9q0/+ a:o bqdzr vydt 30 dB? (See Fig. 12–6.)

  Your auditory system can accommodate a huge range of sound (u.u3 gl tr86b 5yhssrlevels. What is the ratio of highest to lowest intensity at 8(u. 3rt b65ghlrsuys
(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 o 9n m,;h xc98cg-7czrb)prob cf 440 Hz. The length of the vibrating portion is 32 cm, agzbcb)r8 h7o-xc c99cpm n r;,nd it has a mass of 0.35 g. Under what tension must the string be placed?    N

  An organ pipe is 112jns: og 9bri7(91sm iq cm long. What are the fundamental and first three audible ovgr bm:9n7i1s9joi (sq ertones 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 frequency would yod9v:*6bv e kaf+6e e+-lojyofu expect from blowing across the top of an empty soda bottle that is 18 cm deep, if you assumedldf eb- vykj o o9e++a6vf:e6* 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 spannilbe1;m:hx2 l ung the range of human hearing (20 Hz to 20 kHz), what would be the range of the lengths of pipxlu eml:;bh1 2es required? $L_{20 Hz}$ =    m $L_{20 kHz}$ =    $ \times10^{ -3}$m

  A tight guitar string has a frequency of 540 Hz as its third harmonic. W5(kqv,e xgg 8gwgpl v -1c7ps,hat will be its funda,peg-,qwg 5 x7 l(c g1gs8vpkvmental frequency if it is fingered at a length of only 60% of its original length?   Hz

  An unfingered guitar str j agerf7sxye- *.n; 7nd:/xafing is 0.73 m long and is tuned to play E above middle C (330 e.y7jxsanr ge* af- 7 f;:/xdnHz).
(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 qcvgxcyw. )2.r4h gg-middle C (262 Hz) when the te4.rxgyc hgcv .-w qg2)mperature 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 at 208gi) ; )aawfjt $^{\circ} $ C. By what percent will the frequency be off at 5.0 $^{\circ} $ C?    %

  How far from the mouthpiece of the flute in Example 12– h oue5kk)ti6;-bv a8o10 should the hole be that must be uncovered to play D above middle-i ooe); tkku5bah 68v 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 26 2p. -e)bkqouo 9o au7xgdbh f3d61yz04 Hz, 440 Hz, and 616 Hz, but not at any other frou )k yx6o13 bgf7-p ba .0qe2ddz9ouhequencies 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 at1ir6d7: rlc/e ;ulg+t4rfh oj two successive harmonics of frequencies g+1l7hrrlt e/ do ;rucj :i46f275 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 n6 o p1 sg,z1lmp-28lix- 8)cyxctoow$^{\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 niw,(v ri9cmof.ls++ 2.14-m-long organ pifnm ,.livr+s +(9owcipe at 20 $^{\circ} $ C
(a) if it is open,   
(b) if it is closed?   

  The human ear canal is approximatelyi/x jkmm0.2eag45l,x ph6/z( sl josr 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 relationship of your answer tm .6hxpkz/ i(/jg2l, jsmr04a5os elxo the information in the graph of Fig. 12–6? $f_1$ =    Hz $f_3$ =    Hz $f_5$ =    Hz

  A piano tuner hears one bwd qepj*z0e)o nt8)d ,eat every 2.0 s when trying to adjust two strings, one of which is sounding 440 Hz. How far off in frequency is the oth*, )jpotw q0)z e8dneder string? ±    Hz

  What is the beat frequency if middle C (262 H0j0hc4yow c d.z) 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) operates a96phh4x ttm d/4c/q ieix7k;bt an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whi dhhqi /k 4bxxt4p6c9tmi;7/ene 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 when sounded with a 350-qk 8ogx)99qvwf, sl z3k 3d q3z9,omtjHz tuning fork and 9 beavk 3z8dw 3q99s, 9 x)ztgmqqof3ljko,ts/s when sounded with a 355-Hz tuning fork. What is the vibrational frequency of the string? Explain your reasoning.    Hz

  Two violin strings are tuned to the same frequency, 294 Hz. The tension 6*1fnbt b4,t1e;xv zagy1w; pm gsa0 pin one string is then decreased by 2.0%. What will be the beat frequency heard when the two strings are played together? [Hint: Recall Eq. 11–13.4*zbbf 16vm wyspn0agte1ap 1,; ;gxt ]    Hz

  How many beats will be heard if two identical flutes edno(3,+e jf xtach try to play middle C (262 Hz), but one is at 5.0°C and the other at(ej+ 3tfn,xdo 25.0 $^{\circ} $ C?    beats/sec

  You have three tuning forks,k 8614bery.125voud tr igvs0i4eitu 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 frequency is 4 Hz. What are the possible fry so ge8t6kv1iuei.v 4ui 45120drrbtequencies 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 stanr h5/k54q7uil1m;h x0e8zkzgx tjosak8s/ 8k ds 3.00 m from one speaker and 3.50 m from the other. z0zh5 s jkg4u8lx/re; ma8k8/kqhs it5k xo71
(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 132ge ;4hp:ok-dv:q/ht qco2 p f* Hz, but a piano tuner hears three beats every 2.0 s when they are played togp;g4p2 d q:hhe*co:v kt-/oqf ether. (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. How many beats peykbrvr bffv+.es 26,/t ky7bik0 g9d* r s vsy d f/e29kbk+,gyr0f6*bkt7 vrb .iecond will be heard? (Assume T = 20 $^{\circ} $C)$\approx$    Hz(round to one decimal place)

  The predominant frequency of a certain fire engine0h7m,xg oafkipx+ hwww-3 3.g’s siren is 1550 Hz when at rest. What frequenwf kgmx3w .+p7,oah0 x-hig3wcy 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. Wh6 qtjn:4g2+/fb(b jyk dqu 7qsat frequency do you detect if a fire engine whose siren emits at 1550jj f6:tkq 2( by+b/sqqg4u7dn 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 movjllg+s( ,) rdr 6pm.uckp9(jying toward you at 15 m/s versus you moving tj ,p()sp u rygm9l 6drlck(j+.oward 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 equig -fnu7)5k lbpxp:nk ;pped with the same single frequency 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 emifp lkp;) gnku:bxn-57t? Assume T = 20 $^{\circ} $C    Hz

  A bat at rest sends out ultrasonic soun)(bvgumy/a a;j2:bx m d waves at 50.0 kHz and receives them returned from an object moving directly away from it at 25 m/smby /uvmx2a:g; (j )ba What is the received sound frequency?    $ \times10^{ 4}$ Hz

  A bat flies toward a wall at a speed of 5 m/s As it fliesu *;*zjrwkd-uj- i6*sa7)jpo lk: c lz, the bat emits an ultrasonic sound wave with frequency 30.uj;jc -rkjz:u lzlwa-*pos kd 76i*)*0 kHz. What frequency does the bat hear in the reflected wave?    $ \times10^{4}$ Hz

  In one of the original Dopple k3vtm. r r4(1zoy1x+hy,ssqgr experiments, a tuba was played on a 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 b. mhkz1xy1r ,stgs4yor(+3qv eat 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 measure blood-flow speeyvyh-y6vb b+t z p(a50ds. 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 expe-vb06y bt 5y(pav+zhycted 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 of freque4vd)4tb ab r5 d -sngn5sh5ph2ncy $2.25 \times10^{ 6}$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 t:vc u5vj3ry+ q*xh* uqfp q7i8he wind velocity is 12 up7 qv5r*8:fvqh3ux*c y+ijq m/s 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 land if it)w+wsk+vl ju /s 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 sound is 31u.k u71ia rr0s,l( vgb0 m/s (a) What is the angle the shock wave makes with the direction of the0r7 l,sk.gub(ariu1v 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 the2jk mxs3 g /4/i7ev1h p; mcrz4b*zgit speed of sound is only aboutg1zr /4p/32mji7ke *imv gb tcsz 4;xh 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 th5qkk.gsub 07v9*kh ja e shock wave angle it produ*5skga0.qvk9 7jkh buces
(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 dj5ccfsrg)71 . opc 3c$/theta$ 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 1.5 km above 95uqpc evx uiv7 i+n)suq8*:mthe ground flying faster than the speed of sound. By the time you hear the sonic boom, the plane has traveled a horizontal distanceu ipnv5*sm x8c9) i u:ue+qqv7 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 sw4re6quzu7 1t (4 bwsaonar device that sends 20,000-Hz sound pulses downward from the bottom of the boat, and then detects echoes. If the maximum depth for which it is designed to work is 200 m, what is the miwz4rwut46b1 q7(s e uanimum time between pulses (in fresh water)?    s

  Approximately how many octaves are there in the human *b ex ;d)2uc aax9u3uoaudible range? $\approx$    octaves (Round to the nearest integer)

  A science museum has a,) k7tdrx-d .sv-q yxiz/m/ pm display called a sewer pipe symphony. It consists of many py ixms7xd-krmqdp z/v)., -/tlastic 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 cvt4nt g).t47n4rua)jma vxg:3 off6the threshold of human 3j 64v)4u 4af.f) grgt mc7ttx:a onvnhearing (0 dB). What will be the sound level of 1000 such mosquitoes?    dB

  What is the resultant sound level when an 82-dB sound and an 87-dB sound arend 9bf9*ppzt/4*ljb c heard sit*/db4* j9lc n pzf9pbmultaneously?    dB

  The sound level 12.0 m from a loudspeaker, placed in the open, is 105 dB.m md4u0gj dze9*pk5x ,yic5.s What is the acoustic power output (W) of the speaker, asigd4m, my *jkx udz.cp0 s595esuming it radiates equally in all directions?    W

  A stereo amplifier is rated at 150 W output at 1000 Hz. The power outgi3f u3jd 4blx-4my-n put drops by 10 dB at 15 kHz. What is the yfuj3dln x m-3g i44b-power output in watts at 15 kHz?    dB

  Workers around jet aircraft typically wear protectiwinl-dnvn* 6) 5apuavvt 66p/ ve devices over their ears. Assume that the sound level of a j)5l6/ *i6an6v-d aun nvwpvptet 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 distance of 30 m from a jet airplane engine?    W

  In audio and communications systems, ppsd/w6h08bhb vpj rid6 +99 qthe 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 tun.z0xro y i2yz hs9:g+ned 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 fundawnh,kj+y9z*9 k(1ikhaho / xb mental frequency of 440 Hz and a mass per unit le+wk hb1h9zn/( oxj ay,khi9* kngth 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 fill5+h bl;r ccw5bqj3 )nued with water (Fig. 12–35). The water level is allowed to drop slowly. As it does so, the air in tr;+ w qbucnl)jb5c35h he 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 that is open x -ejnhv,tw2ur 6)i)wat one end and also 75 cm long. How much tension should be in the string if it is to produce resonance (in its fundamental moduxe r)n) -v,wji6h wt2e) with the third harmonic in the tube?    $ \times10^{ 2}$ N

A highway overpass was observed to resonate cvz*6i t hah(z(4 uf7s0 ifr(cas one full loop ($\frac{1}{2}\lambda$) when a small earthquake shook the ground vertically at 4.0 Hz. The highway department put a support at the center of the overpass, anchoring it to the ground as shown in Fig. 12–36. What resonant frequency would you now expect for the overpass? Earthquakes rarely do significant shaking above 5 or 6 Hz. Did the modifications do any good?

  A person hears a pure toner81jn 3r.:4z odl ip e.e/b vwx,cn3px in the 500–1000-Hz range coming from two sources. The sound is loudest at points equidistant from the two sources. To determine exactly what the freqnp /pc1 8 x,l iwdn3o.z3b:e4jr .rxveuency 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 condukbw wr. chk;a84;6wqjctor on the stationary train hears a 3.0-Hz beat frequency when the other train approaches. What is the speed of the moving tr8w h;4kacjk qr6ww b;.ain?   m/s

  The frequency of a steam train whistle as it approaches you is 538 Hz pod-npl+ery4 ;1t7 ot np)+qo. After it passes you, its frequency is measured as 486p-;y 1nnpdq) 74++oeloop tr t Hz. How fast was the train moving (assume constant velocity)?    m/s

  At a race track, you can estimate the speed of cars jzd o,dfbe) :x(ust 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 a full octave (frequ :dxdzf b),o(eency halved) as it goes by on the straightaway. How fast is it going?    m/s

  Two open organ pipes, sounjl zbe/g68ht. zv8-bq ding together, produce a beat frequency of 11 Hz. The shortebj8v gle8.q -tz 6/bhzr one is 2.40 m long. How long is the other?    m

Two loudspeakers are at opposite ends of a railroad car as it moves past ad v9-7wclqi w4 stationary observer aqw4iwc d9lv-7 t 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, at B, and (c) he hears the speakers after they have passed him, at C?

  If the velocity of blood flow in the aorta is normapn j3lgv9un rl u:1s w*/o i--a7yuz)jlly about 0.32 m/s what beat frequency would you expect if 5.50-MHz ultrasound waves were directed along the flow andw ip 9u3ugo /a1s*)- njjnlz7 :rvylu- 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-+d cx/1 kcodv speed 6.5 m/s while the moth is flying toward the bat at sp +d/vokdcc-1xeed 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 reflects off the moth?    kHz

  A bat emits a series of high frequency sound pulses as it approachz hk(ilg 7,etf9tb o45es a moth. The pulses are approximately 70.0 ms apart, and each is abogt5 9,f4lzoi7ek(tbh ut 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 is emitted?    m

The “alpenhorn” (Fig. 12–38) was onceetp 7rt2( :gmw 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 instr(gm:p72r tte wument, 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 by tht:) *nutg:*phe0rnwt o j/ v)qe presence of standing waves, which can cause acoustic “dead spots” at the locations of the pressure node:q 0wjhurnt *:*v / ot)e)tnpgs. 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 “singif,rl dbenik1 8*fg/sen5n vnpb+40 l,g;u/eang rods,” involves a long, slender aluminum rod held in the hand near the rod’s midpoint. The rod idke* ;g01fb4s 5ir,+/ /pln ubef ane,vl8gnns 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 threshold of he8yv0d bu,,nddbd1x6hw 7 ;e oraring for the human ear at a frequency of about 1000 Hz 10x dd68 d,yrn7,vbbuwh; edois $I_0$ = $1 \times10^{12 } W / m^2$ 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 th;auf 3f 5php)we ground hears the sonic boom 1.5 min after the plane passes directly overhead. What is 3ufaf)ppwh;5 the plane’s altitude?    $ \times10^{4 }$ m

  The wake of a speedboat is 15 w*o+arqyt62w ii l/mln 2kbx );5fuk,$^{\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