Digital Audio Recording and Editing Techniques

1. Chapter 5Capturing 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 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

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 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 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: • 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

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)