PAThk201hkMidterm
Frequencyhk-hkcorrecthkanswer✔ ✔
Thehknumberhkofhkcycleshkofhkahksoundhkwavehkthathkoccurhkinhkonehksecond.hk
UsuallyhkmeasuredhkinhkHzhk(hertz)hkratherhkthanhkcpshk(cycleshkperhksecond)
SamplehkRatehk-hkcorrecthkanswer✔ ✔
Thehknumberhkofhktimeshkthehkanaloghktohkdigitalhkconverterhkmeasureshkthehk
analoghksignalhkperhksecondhkwhilehkrecording.
NyquisthkTheoryhk-hkcorrecthkanswer✔ ✔
Thehkupperhkfrequencyhklimithkinhkahkrecordinghkishkonehkhalfhkthehksamplingh
krate.
BithkDepthhk-hkcorrecthkanswer✔ ✔
Audiohksignalhkishkmeasuredhkthousandshkofhktimeshkahksecondhkandhkgenerat
eshkahkstringhkofhkbinaryhknumbershkcalledhkwords.hkThehklengthhkofhkahkwordhkc
orrespondshktohkbithkdepthhkorhkresolution.
Whyhkdohkwehkcarehkabouthksamplehkrate/bithkdepth?hk-hkcorrecthkanswer✔
✔
Samplehkratehkaffectshkhighhkfrequencyhkresponse,hkandhkbithkdepthhkaffectshk
thehkdynamichkrange,hknoisehkandhkdistortion.hkWithhkahklowhksamplehkrate,hkhi
ghhkfrequencieshkwillhkbehkweaker,hkandhkwithhkahklowhkbit-
ratehkdynamicshkwillhkbehkdulled,hknoisehkwillhkbehkpresent,hkandhkahksamplehkw
,illhkbehkdistorted.hkThesehkconceptshkarehkveryhkimportanthktohkthehkclarityhkand
hkqualityhkofhksound.hkLowhkbithkdepth hkcanhkalsohkbehkutilizedhkashkanhkeffect.
Whyhkarehkhigherhkbithkdepthshkpreferable?hk-hkcorrecthkanswer✔ ✔
Thehklongerhkahkword,hkthehkmorehkbitshkithkhashkandhkthehkmorehkaccuratehkea
chhksignalhkmeasurementhkis.hkLongerhkwordshkgivehkgoodhkresolutionhk(lowhk
distortion),hkwhereashkshorthkwordshkgivehkpoorhkresolutionhk(highhkdistortion
).
Whathkishkaliasinghkofhkhighhkfrequencies?hk-hkcorrecthkanswer✔ ✔
Aliasinghkishkwhenhkthehksamplinghkratehkishktoohklowhkandhkfalsehkdatahkofhkth
ehklowerhkfrequencieshkgetshkrecorded.hkThehkhigherhkfrequencieshkarehkthenhkd
istortedhkwithhkthehklowerhkfrequencies,hkandhkincorrecthksignalshkarehkreprodu
ced.
Howhkdoeshkanhkanalog-digitalhkconverterhkpreventhkaliasing?hk-
hkcorrecthkanswer✔ ✔ Anhkanalog-
digitalhkconverterhkrunshksampleshkthroughhkahklowhkpasshkfilterhkthathkremove
shkallhkfrequencieshkabovehk20kHzhk(anti-
aliasinghkfilter).hkThehkrangehkofhkhumanhkhearinghkdoesn'thkgohkabovehk20kHz
,hkbuthkifhkthehklowhkfrequencieshkalias,hkthehkeffecthkonhkthehkhighhkfrequenciesh
k(evenhkthosehkabovehk20kHz)hkishkperceivedhkbyhkthehkhumanhkearhkashkdistorti
on.hkThus,hkthehkanti-
aliasinghkfilterhkcutshkouthkthehkhighhkfrequencieshktohkpreventhkaliasinghkbetwe
enhkthehkhighhkandhklowhkfrequencies.
, Howhkdoeshkanhkanalog-digitalhkconverterhkwork?hk-hkcorrecthkanswer✔ ✔
Anhkanalog-
digitalhkconverterhkmeasureshk(orhksamples)hkthehkvoltagehkofhkanhkaudiohkwav
eformhkseveralhkthousandhktimeshkperhksecond,hkquantizeshkithk(generateshkbin
aryhkdigitshkorhk"bits"hkthathkarehkrepresentativehkofhkthehksignal),hkandhkthenhkst
oreshkthehkrecordinghkashkahkmodulatehksquarehkwavehkrecordedhkathkmaximum
hklevel.
WhathkishkthehkRedhkBookhkCDhkStandard?hk-hkcorrecthkanswer✔ ✔
RedhkBookhkishkahkdocumenthkreleasedhkbyhkSonyhkandhkPhilipshkinhkthehk198
0'shkthathkdefineshkthehkstandardshkforhkahkCD.hkAccordinghktohkthehkRedhkBook,
hkCDhkdatahkshouldhkbehkdigitizedhkathk44,100hksampleshkperhksecondhk(44.1kH
z)hkinhkahkrangehkofhk16hkbitshk(65,536hkpossiblehkvalues).
WhathkishkAudiohkQuantization?hk-hkcorrecthkanswer✔ ✔
Quantizationhkishkthehkprocesshkinhkwhichhkahkanalog-
digitalhkconverterhkmeasureshkthehkvoltagehkofhkanhkaudiohkwaveformhkandhkge
nerateshkrepresentativehkbinaryhknumbers.
Whathkdoeshkfrequencyhkresponsehkmean?hk-hkcorrecthkanswer✔ ✔
Ahkgraphhkofhkhowhkahkparticularhkdevicehk(microphone)hkrespondshktohkcert
ainhkfrequencieshkthathkplotshkoutputhklevelhkvs.hkfrequency.hkAhkhorizontalhkli
nehkindicateshkahk"flathkfrequencyhkresponse"hkmeaninghkthathkthehkdevicehklev
elhkishkthehksamehkathkallhkfrequencies.hkMosthkdeviceshkdohknothkhavehkahkflathkfr
equencyhkresponse,hkrather,hktheyhkrespondhktohkahkspecifichkrangehkofhkfreque
ncies.
Frequencyhk-hkcorrecthkanswer✔ ✔
Thehknumberhkofhkcycleshkofhkahksoundhkwavehkthathkoccurhkinhkonehksecond.hk
UsuallyhkmeasuredhkinhkHzhk(hertz)hkratherhkthanhkcpshk(cycleshkperhksecond)
SamplehkRatehk-hkcorrecthkanswer✔ ✔
Thehknumberhkofhktimeshkthehkanaloghktohkdigitalhkconverterhkmeasureshkthehk
analoghksignalhkperhksecondhkwhilehkrecording.
NyquisthkTheoryhk-hkcorrecthkanswer✔ ✔
Thehkupperhkfrequencyhklimithkinhkahkrecordinghkishkonehkhalfhkthehksamplingh
krate.
BithkDepthhk-hkcorrecthkanswer✔ ✔
Audiohksignalhkishkmeasuredhkthousandshkofhktimeshkahksecondhkandhkgenerat
eshkahkstringhkofhkbinaryhknumbershkcalledhkwords.hkThehklengthhkofhkahkwordhkc
orrespondshktohkbithkdepthhkorhkresolution.
Whyhkdohkwehkcarehkabouthksamplehkrate/bithkdepth?hk-hkcorrecthkanswer✔
✔
Samplehkratehkaffectshkhighhkfrequencyhkresponse,hkandhkbithkdepthhkaffectshk
thehkdynamichkrange,hknoisehkandhkdistortion.hkWithhkahklowhksamplehkrate,hkhi
ghhkfrequencieshkwillhkbehkweaker,hkandhkwithhkahklowhkbit-
ratehkdynamicshkwillhkbehkdulled,hknoisehkwillhkbehkpresent,hkandhkahksamplehkw
,illhkbehkdistorted.hkThesehkconceptshkarehkveryhkimportanthktohkthehkclarityhkand
hkqualityhkofhksound.hkLowhkbithkdepth hkcanhkalsohkbehkutilizedhkashkanhkeffect.
Whyhkarehkhigherhkbithkdepthshkpreferable?hk-hkcorrecthkanswer✔ ✔
Thehklongerhkahkword,hkthehkmorehkbitshkithkhashkandhkthehkmorehkaccuratehkea
chhksignalhkmeasurementhkis.hkLongerhkwordshkgivehkgoodhkresolutionhk(lowhk
distortion),hkwhereashkshorthkwordshkgivehkpoorhkresolutionhk(highhkdistortion
).
Whathkishkaliasinghkofhkhighhkfrequencies?hk-hkcorrecthkanswer✔ ✔
Aliasinghkishkwhenhkthehksamplinghkratehkishktoohklowhkandhkfalsehkdatahkofhkth
ehklowerhkfrequencieshkgetshkrecorded.hkThehkhigherhkfrequencieshkarehkthenhkd
istortedhkwithhkthehklowerhkfrequencies,hkandhkincorrecthksignalshkarehkreprodu
ced.
Howhkdoeshkanhkanalog-digitalhkconverterhkpreventhkaliasing?hk-
hkcorrecthkanswer✔ ✔ Anhkanalog-
digitalhkconverterhkrunshksampleshkthroughhkahklowhkpasshkfilterhkthathkremove
shkallhkfrequencieshkabovehk20kHzhk(anti-
aliasinghkfilter).hkThehkrangehkofhkhumanhkhearinghkdoesn'thkgohkabovehk20kHz
,hkbuthkifhkthehklowhkfrequencieshkalias,hkthehkeffecthkonhkthehkhighhkfrequenciesh
k(evenhkthosehkabovehk20kHz)hkishkperceivedhkbyhkthehkhumanhkearhkashkdistorti
on.hkThus,hkthehkanti-
aliasinghkfilterhkcutshkouthkthehkhighhkfrequencieshktohkpreventhkaliasinghkbetwe
enhkthehkhighhkandhklowhkfrequencies.
, Howhkdoeshkanhkanalog-digitalhkconverterhkwork?hk-hkcorrecthkanswer✔ ✔
Anhkanalog-
digitalhkconverterhkmeasureshk(orhksamples)hkthehkvoltagehkofhkanhkaudiohkwav
eformhkseveralhkthousandhktimeshkperhksecond,hkquantizeshkithk(generateshkbin
aryhkdigitshkorhk"bits"hkthathkarehkrepresentativehkofhkthehksignal),hkandhkthenhkst
oreshkthehkrecordinghkashkahkmodulatehksquarehkwavehkrecordedhkathkmaximum
hklevel.
WhathkishkthehkRedhkBookhkCDhkStandard?hk-hkcorrecthkanswer✔ ✔
RedhkBookhkishkahkdocumenthkreleasedhkbyhkSonyhkandhkPhilipshkinhkthehk198
0'shkthathkdefineshkthehkstandardshkforhkahkCD.hkAccordinghktohkthehkRedhkBook,
hkCDhkdatahkshouldhkbehkdigitizedhkathk44,100hksampleshkperhksecondhk(44.1kH
z)hkinhkahkrangehkofhk16hkbitshk(65,536hkpossiblehkvalues).
WhathkishkAudiohkQuantization?hk-hkcorrecthkanswer✔ ✔
Quantizationhkishkthehkprocesshkinhkwhichhkahkanalog-
digitalhkconverterhkmeasureshkthehkvoltagehkofhkanhkaudiohkwaveformhkandhkge
nerateshkrepresentativehkbinaryhknumbers.
Whathkdoeshkfrequencyhkresponsehkmean?hk-hkcorrecthkanswer✔ ✔
Ahkgraphhkofhkhowhkahkparticularhkdevicehk(microphone)hkrespondshktohkcert
ainhkfrequencieshkthathkplotshkoutputhklevelhkvs.hkfrequency.hkAhkhorizontalhkli
nehkindicateshkahk"flathkfrequencyhkresponse"hkmeaninghkthathkthehkdevicehklev
elhkishkthehksamehkathkallhkfrequencies.hkMosthkdeviceshkdohknothkhavehkahkflathkfr
equencyhkresponse,hkrather,hktheyhkrespondhktohkahkspecifichkrangehkofhkfreque
ncies.
