1. Chapter 5 Capturing and Editing Digital Audio

2. Ways to Acquire Digital Audio
Record
Digitize analog medium

3. Recording: Hardware Requirements
Computer with a sound card
Almost all computers nowadays are equipped with a sound card.
Sound card: converts the electrical signals into digital format through sampling and quantization of the signals
Microphone
built-in the laptop Usually does not produce sufficient sound quality
external microphone

4. Microphones Unidirectional Omnidirectional
Most sensitive to sound coming from the front
Advantage: Ignore noise coming from the rear
Omnidirectional
Sensitive to sound coming from all directions
If you don't have the specifications of a microphone
Place the sound source directly in front of the microphone

5. Recording: Software Requirements
Digital audio recording program
Also lets you edit audio
Some common programs:
Adobe Audition
Sony Sound Forge
Audacity (free, open-source)

6. General Steps For Recording With a Digital Audio Program
Start a new file
Specify settings:
sampling rate
bit depth
number of channels
If possible,
run through or reherse the audio you want to record while observing the sound input level
adjust the sound input level so it stays below the red area for the whole audio run-through
Hit the record button to start recording, stop button to stop

7. Settings Sampling Rate Bit Depth Setting Number of Channels Setting
44,100 Hz: CD Quality
22,050 Hz: Sufficient for multimedia projects with voice over and loop musics
Bit Depth Setting
8-bit
usually sufficient for speech
in general, too low for music
16-bit
for music
Number of Channels Setting
1: mono
2: stereo

8. Preferences Dialog in Audacity

9. Audio Level Meter in Audacity
Input volume slider
Input level meter

10. Microphone Level Adjustment in Windows

11. Microphone Level Adjustment in Windows

12. Microphone Level Adjustment in Mac OS X

13. Field/Outdoor Recording
Voice recorder apps on cell phones:
Not intended for high quality audio
Usually mono
File format: Lossy compression to produce smaller file size suitable for and uploading to Web from the phone
To transfer the audio to computer:
Common method: it to yourself as attachment and check your s on your computer to detach the file
iPhone: Can also use iTunes
Android phones: Connect the phone to your computer as a drive

14. Basic Editing One audio at a time Audio mixing with multiple audio
enhance audio (such as trimming, remove nosie) even if it is for use in audio mixing
Audio mixing with multiple audio

15. One Audio at a Time Basic workspace elements: Waveform display
x-axis: time
y-axis: audio amplitude
mono: 1 waveform
stereo: 2 waveforms on top of each other
Transport controls (play, record, rewind, fast forward buttons)

16. Audacity
waveform display
Transport controls

17. Audio Mixing: Working with Multiple Audio
Example applications:
mix multiple instrumental playback where each is recorded as a separate audio
compose audio with multiple clips
voice-over with background music

18. Audacity
track 1
track 2

19. Audio Mixing vs. Recording Everything All Together
Record audio clips separately and mix them later
Record everything all together at once

20. Advantage of Audio Mixing
Allow you to adjust the volume level and apply effects (such as fade-in and fade-out) to each audio independently
Examples:
You can adjust relative volume of the voice-over and the background music if you record the voice-over and background music as two separate audio.
You can insert a silence in the voice-over if needed for controlling the timing.

21. Parallels between Basic Digital Image and Digital Audio Editing
Basic Digital Image Editing
Basic Digital Audio Editing
Reassemble image content by cutting, copying, and pasting
Reassemble audio waveform by cutting, copying, and pasting
Adjust tonal value
Adjust volume
Clean up dirt, dust, and scratches
Noise reduction
Resize the image
Resample the audio
Reduce the image’s color depth
Reduce the audio’s bit depth
Apply filters for special effects
Apply filters for special effects, such as reverb and pitch changes
If you want to save your file as JPEG for the Web, wait until the last step because JPEG uses lossy compression
If you want to save your file as MP3 for the Web, wait until the last step because MP3 uses lossy compression

22. Reassembling Waveform
To select a segment of a waveform: Click-drag to select
You can cut, copy, or delete the selection
To paste a segment of a waveform:
Click at position you want to paste
Paste (Usually, Edit > Paste)

23. Reassembling Waveform Example1 2 3 4
Original recording of saying:
The segment for "2" is selected 2 1 3 4
The segment for "2" is cut and pasted before "1". Now, the audio says:

24. Changing Volume
When the original audio is too soft or too loud for the intended use
When composing multiple audio that do not have a consistent volume level—some too soft and some too loud
When you want to fade in or out an audio

25. Common Functions for Changing Volume
Amplify: lets you specify amplification in a dB (decibels) or percentage
Normalize:
lets you set a peak level for a file or selection
amplifies the entire file or selection so that the highest level is the peak level you specify

26. Common Functions for Changing Volume
Fade in: suppresses the volume at the beginning of the audio
Fade out: suppresses the volume at the end of the audio
Envelope:
lets you use a curve to specify the ups and downs of the volume over the course of the audio
can create fade-in and fade-out effect

27. Noise Reduction Useful for removing background noises, such as:
computer fan noise
hissing noise of the microphone
To reduce noise that is constant throughout the audio
The noise may contain wide ranges of frequency

28. Noise Reduction How it Works
You select a segment that contains pure noise.
The program performs a statistical analysis of the noise to generate a profile.
The program reduces the noise of the whole audio (or selected segment) based on the noise profile.
Audacity: Noise Removal

29. Special Effects Change of pitch Change of speed
chipmunk voice (higher pitch)
Darth Vader voice (lower pitch)
Change of speed
helium voice (faster speed)
slow-motion voice (slow speed)
Reverb Create the feel from being in a large empty auditorium to a small bathroom.

30. File Size Consideration
Best to record and work with audio at CD-quality levels (i.e., 44,100 Hz sampling rate, 16-bit, and stereo) or higher
When delivering the final audio, depending on the project, you may need to lower the file size:
downsample the file to lower the file size
export to MP3

31. Types of Music Creation
MIDI:
create original music scores
require musical composition skills
Loop music composition
compose a long musical audio through repetitions of short musical clips
common in projects that do not require a long musical score, for example:
game development, product advertisements, digital art projects
allow non-music composers to create musical audio

32. MIDI Not sampled audio Like sheet music
Constains instructions for recreating the music
Created by editing music notations and instrument assignments
Can also be created by recording your performance on a MIDI keyboard connected to a computer
Playback of a MIDI file requires a sound card that uses the synthesizer to recreate the sound of notes

33. MIDI Playback
Requires a sound card that uses the synthesizer to recreate the sound of notes
Not all synthesizers produce the same sound
Disadvantage: How the music actually sounds during playback depends on the sound card

34. Loop Music
Music that is created from short music clips that are repeated
Usually designed to loop seamlessly
Libraries of clips for loop music are commercially available

35. Composing Music Using Loop Music
Programs support multi-track
Import an audio clip to place on a track
Create repetitions of a clip placed on a track simply by dragging its right edge to extend it
You can adjust the volume of each track to fade in or out the clips

36. Uses of Digital Audio Video Multimedia authoring Playback on the Web
Audio CD
Podcast

37. Video and Multimedia Authoring
Export audio and import it into the video editing or multimedia authoring program
Most video editing program support:
.wav
.aif
mp3
Adobe Flash supports:
.au
.mp3
audio-only QuickTime

38. Playback on the Web Best if small file size for less wait time
HTML5 audio
Streaming format
Progressive download

39. Methods to Play Back on the Web
Embedding the audio on the Web page
HTML5 audio
Played using the browser's built-in player
Non-HTML5 audio
Played using plug-in or external player
Linking to the audio file
will cause the file to play in an external player window

40. HTML5 Audio Supported formats: MP3, ACC (MP4), OGG Vorbis, and WAV
HTML5 <audio> tag:
Example usage:
<audio src="demo.oga" controls>
An introduction of HTML5 video and audio is covered in Chapter 9

41. QuickTime Audio-Only Movies
Can be exported using video-editing programs (Adobe Premiere Pro, Apple Final Cut Pro)
Fast-start movies: Allow progressive download—the audio will start to play as soon as enough data have been downloaded.

42. Audio CD
Must use:
sampling rate: 44,100 Hz
bit depth: 16
stereo
Audio editing programs (such as Adobe Audition) also let you create audio CD projects:
title and artist for each track
length of pauses between tracks
enable/disable copy protection
ISRC number

43. Podcast Podcast: Episode: Feed:
a collection of files available on a Web server
usually audio files
can be any types of files: Web pages, text, PDF, images, ...
Episode:
Each file in the podcast
Feed:
The text file that lists the internet addresses of the files in a podcast.
Posted on a Web server
People subscribe to the feed

44. How Podcast Works
Whenever a new episode is available, it will be automatically downloaded to the subscriber's computer or device (e.g. iPod)
The software program that periodically checks and download the new items is called aggregator (e.g. iTune)