Media Studies Chapter 5 Homework Change the channel to stereo, keeping at 44,100 Hz sample rate

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Lab: Digital Audio Manipulation

SoftwareRequirement:AdobeAuditionCS3orabove.Theinstructionsandscreenshotsusedherewere

basedfromAuditionCC2014.

Objectives of this lab:

1. Distinguishbetweenaudiosamplingrateandaudiofrequency

2. RecordavoiceinAdobeAudition,removebackgroundnoise,rearrangethewaveform,and

applysoundeffects

3. Frequencyanalysisofhumanvoice

5. LearnwhattypeofinformationislostwhensavingMP3files

6. Learntheeffectsofsamplingrate,resolution(bitdepth),andchannelnumberonfilesize

Lab Instructions:

I.DistinguishAudioSamplingRatefromAudioFrequency

Downloadfoursingletonesfilesfromthebook’sWebsite.Listentothesefoursingletones.Notethe

differenceinthepitch.

Thesamplingratesandtheaudiofrequenciesofthesesingletonesarelistedinthefollowingtable:



FileFilenameSamplingRateBaseFrequencyoftheSingle‐tone

1tone-sr-44100-base-1000.wav 44,100Hz1000Hz



Q1.Multiple‐choice:Withthesamebasefrequencyofthetone,increasingtheaudio

A.increasesthepitchofthetone

B.decreasesthepitchofthetone

C.doesnotchangethepitchofthetone



A.increasesthepitchofthetone

B.decreasesthepitchofthetone

C.doesnotchangethepitchofthetone



III.Recordyourvoiceandremovethebackgroundnoise

1) CreateanewfileinAudition.Todoso:

Atutorialmovieshowing

howtorecordaudioin

Page2of8



3) Applyanoisereductionasshowninthetutorialtoremovethebackgroundnoise.

Todothis:

i. Selectaportionofthewaveformthathasjust“noise”(forexample,thesegmentat

thebeginningbeforethe“a”).

4) SavetheaudiofileasaWindowsPCM(voice.wav)file.



Figure1.NoiseReductiondialogbox

IV. Rearrange the waveform

1) Withthevoice.wavstillopeninAudition,rearrangeyouraudioabovetosound“cab”by

V. Frequency analysis of human voice



Atutorialmovieshowing

Auditionisavailableatthe

Page3of8



3) Playtheaudio.Observethegraphofthefrequency.

Thex‐axis(lefttoright)representsfrequency(measuredinHz),whilethey‐axis(bottomtotop)

correspondstotheamplitudeofthecorrespondingfrequency(measuredindB)onthex‐axis.



Figure2.Frequencyanalysiswindow



Q3.Multiple‐choice:Inthefrequencyanalysisgraph,youmaynoticethatthehigh

amplitudeconcentratesonacertainrangeoffrequency,whichistherangeof

audiofrequencyofyourspeechinthisrecording.



Fromthefrequencyanalysisofyourspeechandotherstudents’(lookatother

students’ifpossible),whatistherangeofaudiofrequencyofhumanspeech?A

VI. Effect of sampling rate on the file size

1) Savethevoice.wavasvoice-lower-sample-rate.wav.



3) Changethesamplingrateto6,000Hz,keepingat16‐bitresolutionandmono.

4) Savetheaudiofileandcloseitafteryouhaveansweredthefollowingtwoquestions.



Q5.Multiple‐choice:Listentobothaudioandnotethedifferenceintheaudioquality.

Thevoice-lower-sample-rate.wavisdistortedsuchthatitlosesthe_____

frequencyrangeoftheaudiocomparingtothevoice.wav.(Tip:Alsousethe

A.higher

B.lower



VII. Effect of number of channels on the file size

1) Reopenvoice.wav(donotstartwithvoice‐lower‐sample‐rate.wav)andsaveitasvoice-



3) Changethechanneltostereo,keepingat44,100Hzsamplerateand16‐bitresolution.



4) Savetheaudiofileandcloseit.

A.Thefilesizeofvoice-stereo.wavisabouttwiceofthatofvoice.wav

(mono).

B.Thefilesizeofvoice-stereo.wavisabouthalfofthatofvoice.wav

(mono).



VIII. Effect of resolution (or bit-depth) on the file size

1) Reopenvoice.wav(donotstartwithvoice‐lower‐sample‐rate.wav)andsaveitasvoice-

8bit.wav



3) SelectEdit>ConvertSampleTypes…



5) Savetheaudiofile.

A.Thefilesizeofvoice-8bit.wavisabouteighttimesofthatofvoice.wav

(16‐bit).

B.Thefilesizeofvoice-8bit.wavisabouttwiceofthatofvoice.wav(16‐bit).

C.Thefilesizeofvoice-8bit.wavisabouthalfofthatofvoice.wav(16‐bit).

D.Thefilesizeofvoice-8bit.wavisabout1/8thofthatofvoice.wav(16‐

bit).

E.Thefilesizeofvoice-8bit.wavisaboutthesameasthatofvoice.wav(16‐

bit).



Q8.Multiple‐choice:Listentobothaudioandnotethedifferentintheaudioquality.

A.better

B.worse



IX. Audio file type: .WAV vs. .MP3; and MP3 being lossy compression

1) Openmusic.wavinAudition.Dothefollowingstepstosavethefileasmusic.mp3:

i. File>Saveas…



A.music.wav

B.music.mp3



2) Closemusic.mp3andreopenitinAudition.

(Youneedtoclosethefileandreopenitinordertoseetheeffectinthenextstep.)



3) Lookatthespectralviewofbothmusic.wavandmusic.mp3.

Note:Tolookatthespectralviewofanaudiofile,selectView>ShowSpectralDisplay.



Thespectralview(Figure3)showstheaudiofrequencyversustime.Theintensityofthecolor

Page6of8



(a)



(b)

Figure3.(a)Spectralviewofmusic.wav.(b)Spectralviewofmusic.mp3.



Q10.Multiple‐choice:Bycomparingthespectralviewofmusic.wavand

music.mp3,youseesomeaudiofrequencyrangesarelostinthemusic.mp3

A.thehighfrequencyrange

B.thelowfrequencyrange



ThefrequencyrangethatislostintheMP3fileisnotperceivablebytheaveragehumanearinthe

presenceoftheotheraudiofrequencyrangesinthefile.ThisisthebasicideaoftheMP3compression.

That’swhythefilesizeofMP3canbesosmall;ithasmuchlessdataandthedataisnotexactlythe

sameastheoriginaluncompressedfile.Butitstillsoundsgood.



4) TohearwhatislostinthisMP3file:

i. openthemusic.wavfile

Page7of8

ii. inthespectralview,selecttheregionabove16,000Hz,copyandpasteitintoanewfile

(Figure4)

iii. playthisnewfile

Dependingonyourcomputer’ssoundcardandyourcomputerspeaker,youmayormaynot

beabletohearthishighfrequencyrange.



Figure4.Spectralviewofthenewfilecontainingthefrequencyabove16,000Hzoftheoriginalmusic.wav.



OpenoneofyourfavoriteMP3musicfiles,ifyouhaveoneonyourcomputer.Lookatitinthespectral

view.DependingonthemusicandthecompressionsettingofyourMP3filewhenitwascreated,you

maybeabletoseethatthereisanapparentfrequencyrangemissingfromyourMP3file.

X. Apply a pitch-change audio effect to your audio

1) Reopenyouraudiofile,voice.wav,andsavethefileaspitch.wav.



2) Changethepitchoftheaudio(Effects>TimeandPitch>StretchandPitch…)bymovingthe

slider.

Page8of8



Figure5.StretchandPitchdialogbox



3) ClickOK,andplaytothestretchedandpitchshiftedaudio.Savethefile.

XI. Apply a reverb effect to your audio

1) Openyouraudiofile,voice.wavandsavethefileasreverb.wav.



2) Applyareverbeffect(Effects>Reverb>Reverb…).