What can we do with digital audio that is meaningful -- that is worth the effort?

1. Why do it?
   
   
   • foreign language
   • spoken word in foreign language -- poems -- pronunciation
   • sung words (foreign language)
   • "flavor" -- instrumental music (e.g., Peruvian music for a Spanish instructional module)
   • music as content (e.g., French Popular song course, Jazz History course)
   • historical spoken word -- e.g., Nixon and LBJ Oval Office recordings -- History and Politics Out Loud

   In-class lecture presentation only?
   Casual student review?
   Intensive student study?
   Students include digital audio excerpts in papers?

   user must be able to

   • turn sound off
   • control volume
   • pause sound
   • know "where they are" -- how much further to go
   
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2. Why not?
   
   
   • Don't do it just because you can
   • People can, generally, read faster than they can hear (so an audio version of a speech might not be the best way to present it -- although people can attend to audio while they're looking at pictures)
   • If native language, do not do audio *and* text -- do one *or* the other
   
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3. Examples
   
   
   • French 103 FirstClass conference -- Poèmes -- Recatonpilu;
     Chansons -- Madeleine;
   • English 213 FirstClass conference -- A/V Aids to Chaucer -- Canterbury Tales -- First 42 lines Also on English Dept web site
   • French poetry (Baudelaire, Rimbaud, Verlaine)
   • German songs from Comedian Harmonists
   • French in Action - audio program from textbook
   • Los Pollitos - childrens' songs and nursery rhymes
   • Classical Chinese fables - audio with changing still images; question (in audio) with multiple choice

   For French poems -- audio with synchronized text track
   poems memorized for oral presentations
   best way to give students an oral model of text they need to recite
   previously used audio tapes, but they're too cumbersome to manipulate
   memorization best facilitated by repeatedly listening to small segments
   can loop -- either a whole poem or certain section of a poem

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4. How to do it -- 3 steps -- capture, edit, and compress
   
   a) Capture (digitize) the sound
   
   
   • sources -- microphone (use special audio room at Knapp), audio CD, grabbed from web, from digital audio tape (DAT), from cassette deck, from videotape or laserdisc or DVD, from camcorder
   • if using microphone: garbage in, garbage out -- no background noise; no hum from ventilation system
   • digitize at 44.1kHz sample rate, 16 bit sample size (a.k.a. sample resolution)
   • You can check out a special Marantz solid state recorder from Knapp that records audio directly to .wav files onto compact flash cards for easy file transfer

   
   b) Editing the sound

   Software

   • On the Mac, our current standard sound editor is Amadeus II (shareware for which we purchased a site license for Wellesley); another good shareware sound editor is Sound Studio;
   • A free sound editor that's available for Mac OS X, Windows, and Linux is Audacity.
   • As of July 2000, the special audio production room in Knapp has a very sophisticated sound editing application called ProTools LE.
   • You can also can use iTunes (which can capture and compress audio from CD in one step) or QuickTime Player to grab audio from audio CDs
   • On Windows, good shareware is GoldWave ($40); other applications include SoundForge and Adobe Audition

   in and out points
   delete pops, or pauses, or "ummmms"

   Effects

   • Normalizing (just like "sharpening" on scanners) -- finds highest peak and amplifies the whole sound to its maximum value without clipping or distortion -- raises amplitude of sound to its highest distortion-free level without manual amplitude adjustments.
   • Denoising and sound repair -- removes sharp edges, clicks, and pops -- can be used to eliminate hiss and static, but be careful not to make the sound worse.
   • Fade In or Fade out

   
   c) Compressing the sound

   Keep quality as high as you can while keeping the data rate (file size) small -- thus the download speed is rapid

   1 second of stereo sound (digitized at 44.1 kHz and 16 bits) = 1376 kilobits (or 172 KBytes) 10.3 MB/min

   1 minute of mono sound (digitized at 44.1 kHz and 16 bits) = 688 kilobits (or 86 Kbytes) 5.1 MB/min.

   After you compress a sound, you can't use effects -- so only do it after you've done all your editing.

   Also -- be sure to save an uncompressed version for archiving purposes (and to have a high quality file from which to try out different compression schemes.)

   • 4:1 IMA/ADPCM -- the oldest compression scheme -- also works with QuickTime 2.x
   • QDesign Music -- introduced with QuickTime 3.0 in 1998-- for music -- data rates of anywhere between 8 kilobits/sec and 48 kilobits/sec, but it is optimized for 24Kbps. Data rate does not double with stereo. The codec finds contents in common between the two tracks so the increase in data rate between mono and stereo is only 20-30%.
   • QualComm PureVoice -- also new with QT 3.0 -- designed for native language speech -- compression rate of either 9:1 or 19:1. Has a very noticeable artifact though of making speech sound like it was recoreded underwater :-)
   • MP3 -- compression to 1/10 or less of original (uncompressed) size
     • MP3 stands for Motion Pictures Expert Group MPEG-1, layer 3 audio
     • As of mid-to-late 1990s, it became the most popular way of compressing music
     • Leonardo Chiariglione, one of the key engineers who created MPEG, said in an interview with Scientific American in March 2004, "When we approved the standard in 1992 no one thought about piracy. PCs were not powerful enough to decode MP3, and internet connections were few and slow. The scenario that most had in mind was that companies would use MP3 to store music in big, powerful servers and broadcast it. It wasn't until the late '90s that PCs, the Web and then peer-to-peer created a completely different context."
     • While you can choose many different bitrates for MP3, most folks end up using 128 kilobits per second for music recorded in stereo, and 64 kilobits per second for music in mono
     • QuickTime Player cannot create MP3 files; it can only play back MP3 audio

   How do you compress?
   
   How do you compress? We suggest using iTunes. Other applications that can compress audio into MP3 files include Amadeus II, Media Cleaner Pro, and dozens of others.
   

   How do you embed a QuickTime audio file in a web page?
   
   If you are using Dreamweaver, follow the instructions for inserting QuickTime movies into web pages.
   
   If you are hand-coding, you can add the HTML yourself:
   To do this you must use both <EMBED> and <OBJECT> tags.
   

   <OBJECT classid="clsid:02BF25D5-8C17-4B23-BC80-D3488ABDDC6B" width="240" height="16" codebase="http://www.apple.com/qtactivex/qtplugin.cab">
   < param name="src" value="moviename.mov">
   < EMBED SRC = "moviename.mov" WIDTH = 240 HEIGHT = 16 pluginspage="http://www.apple.com/quicktime/download">
   < /embed>
   < /object>

   Use poster movies if more than one or two sounds per page
   
   What are your source files -- mono? stereo?
   
   All music recorded in the US before around 1958 is mono. Many recordings between 1958 and 1968 are stereo. Almost all American recordings after 1968 are stereo. To be sure a recording is in stereo, take a look at the two tracks in a sound editing application such as Amadeus II. If it's stereo, the tracks are different -- occasionally subtly so. It may help to normalize the audio to reveal the different wave patterns.

   What's the source -- from CD? from cassette? from DAT? from microphone?
   
   What's the sample rate -- 22.05 kHz? 44.1 kHz?
   
   Which codec is best to use?
   
   For speech in a foreign language, use MP3 compression.

   • Settings to use for MediaCleaner Pro
     
     • Output should be MPEG Layer-3
     • Audio -- Sample Rate should be 44.1kHz; Data Rate should be 64 kbits/sec; Channels should be Mono; Speed -- probably 5, but experiment -- if you're really fussy, you can set it at 9; Volume -- Normalize at 95
       
   • Audio filters in Media Cleaner Pro can help remove unwanted noise. Be sure to test these filters first where the Output Format is a QuickTime Movie and the Audio Codec is set to None.
     
     • To reduce a high pitched whine, use the Low Pass filter (it lets frequencies lower than x pass through)
     • To remove a low rumble (such as you get from ventilation systems), use the High Pass filter
     • To remove the noise from a power line, use the Notch filter
     • There's also an adaptive Noise Removal filter which can remove white noise (hiss, static) as well as colored noise (power line noise, hum, hard drive noise, etc.). It can be set to Mild, Moderate, Extreme, or Custom.
     • Dynamic Range -- lets you boost the volume of quiet sections, and limit the loudness of loud sections. Unlikely to use this, but...
       
       
   • For stereo music, also use MP3 compression, but use a Data Rate of 128 kbits/sec. (Note: If folks with modems are using this site, you might be better off with QuickTime files that use the QDesign 2 codec, which often works better than MP3 at low bandwidth.)
     
   • For mono music recorded after 1950, use MP3 compression with a Data Rate of 64 kbits/sec.
     
   • For mono recorded before 1950, use MP3 compression with a Data Rate of 48 kbits/sec.

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5. Formats
   

   QuickTime is a multimedia architecture that can handle all these audio formats

   • .aif audio interchange file format (Mac native; usually not compressed; roughly 688kbits/sec for monophonic CD quality sound)
     
   • .wav Windows native
     
   • .au Sun (Internet) native
     
   • .mp2 MPEG Audio layer II
     
   • .mp3 MPEG Audio layer III (even better than mp2 for compression, supported in QuickTime 4.0 and later)
     
   • .dif audio that comes from Digital Video cameras
     
   • .AAC Advanced Audio Coding (higher quality than MP3 at low data rates; support for multichannel audio; used by iTunes Music Store allows for Digital Rights Management [FairPlay]) For more info, see info on AAC on Apple's web site)
     
   • Apple Lossless Encoder (full quality of uncompressed CD audio using about half the storage space)
     
   
   

   Advantages of QuickTime

   • fast-start
   • multiple audio tracks
   • synchronized text track
   • multiple data rates
   • HREF text track
   
   

   Disadvantages of QuickTime

   • requires a plug-in
   • not designed for very large chunks of audio or video. Our rule of thumb -- fast-star QuickTime audio files should be no larger than 5 to 10 minutes. For audio which cannot be chunked into segments less than 10 minutes, you should consider streaming audio (either QuickTime streaming or RealAudio.)
   
   

   A note about MIDI

   MIDI files are an extremely compact way to store music on a computer. Instead of storing audio samples like most audio file formats (wav, aif, mp3, etc.), MIDI files store only information about sequences of musical notes and instruments instead. MIDI files contain a small fraction of the data of traditional digital audio formats

   In the past, computer users would have to buy special purpose sound cards or external MIDI keyboards to be able to listen to MIDI files. QuickTime 3.0 contains a built-in software only music synthesizer which lets you play back MIDI files on any personal computer with QuickTime 3.0 or later installed.

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Created by: Tuyet Nguyen '01 and Erin Foti '04
Maintained by: Kenny Freundlich, kfreundlich@wellesley.edu
Information Services
Date Created: December 29, 2003
Last Modified: June 5, 2006
Expires: December 1, 2007