Chapter 5 Capturing and Editing Digital Audio

1. Chapter 5Capturing and Editing Digital Audio “Computers and Creativity” Richard D. Webster, COSC 109 Instructor Office: 7800 York Road, Room 422 | Phone:  (410) 704-2424 e-mail: webster@towson.edu 109 website:  http://pages.towson.edu/webster/109/

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 laptopUsually does not produce sufficient sound quality • external microphone

4. Microphones • Unidirectional • 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 • 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 inAudacity

9. Audio Level Meter inAudacity Input volume slider Input level meter

10. Microphone Level Adjustment in Windows 7

11. Microphone Level Adjustment in Windows 7

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 email and uploading to Web from the phone • To transfer the audio to computer: • Common method: Email it to yourself as attachment and check your emails 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 • 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

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

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 forChanging 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 forChanging 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 ReductionHow 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 • chipmunk voice (higher pitch) • Darth Vader voice (lower pitch) • Change of speed • helium voice (faster speed) • slow-motion voice (slow speed) • ReverbCreate 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: • .wav • .aif • .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 15

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. RealAudio • Can be streamed • require a Real Server—a streaming server • Can also be used on the Web without streaming • .ra or .rm file • converted from a .wav using RealProducer Basic (free) or RealProducer Plus

43. 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

44. Podcast • Podcast: • 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 thatlists the internet addresses of the files in a podcast. • Posted on a Web server • People subscribe to the feed

45. 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)