DIGITAL AUDIO BASICS

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1 DIGITAL AUDIO BASICS 81

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15 STUDY GUIDE Digital Audio Basics You are responsible for knowing and understanding the following concepts and information concerning digital audio. 1. Define digital audio. 2. What are some things that utilize digital audio that we encounter in everyday life? 3. What is the difference between analog sound and digital audio? 4. What is a sample? 5. Describe the process of sampling, or A-D conversion. 6. Define bit depth. 7. Define sampling rate. 95

16 8. What is the industry standard bit depth and sampling rate for: Bit Depth Sampling Rate CD Audio: DVD Video: DVD Audio: 9. Describe the process of D-A conversion: 10.What is a buffer? 11.When does clipping occur? 12.What is a noise floor? 13.What is decibel and what is it used for? 96

17 14.What is the threshold of hearing? 15.What is the threshold of pain? 16.Define signal-to-noise ratio or S/N ratio. 17.How is S/N ratio calculated (expressed in db)? 18.What is error correction and why is it important? 97

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19 Date Due: Name: WORKSHEET How Analog and Digital Recording and CDs Works 1. What were two problems with analog recording? a) b) 2. What were the two goals of digital recording? a) b) 3. What is meant by fidelity? 4. What two things affect the fidelity of a digital recording? a) b) 5. What is the sampling precision (bit-depth) of CD audio? 6. What is the sampling rate of CD audio? 7. Name the four layers of a compact disc. (See Cross-Section of a CD ) a) b) c) d) 8. How wide are the bumps on a CD? 99

20 9. How does a CD player read a CD? 10. What is the job of the tracking system? 11. Define the following: a) Subcode data - b) Error correcting codes - c) Interleaving - 100

21 DP4 DRILL 14 Importing Digital Audio Import audio, Soundbite window, Waveform editor, Snip, Stereo Audio Track, Input, Output, Track Window Ruler 1. Open a new DP4 project and save it as Drill 14.x. 2. Use the following procedure (steps 3, 4 & 5) to import and edit sound effects into DP4. a. Create a story using only sound effects. b. You may use multiple audio tracks to overlap sound effects, if you wish. c. Use Stereo tracks because all of the sound effects are stereo audio files. 3. Import a sound effect from the Sound Effects folders a. Open the Soundbites window (Shift+B) b. From the Mini Menu in the Soundbites menu, select Import Audio c. Navigate to your source of audio (folders but this can also be a CD or MP3 file, itunes file, Apple Loop, etc.) i. The Sound Effects are in: Applications MOTU DP4.6 Folder Sound Effects ii. There are two folders in there, each with 100 sound effects check the black binder for lists of files iii. To audition the sound files, click the speaker button on (lower right) so it is yellow. Then highlight the sound you wish to hear and it should play. d. Select the file(s) you wish to import and click Open e. The selected files should show up in your Soundbites window in DP4 4. Edit the soundbite in the Waveform Editor a. Open your second Main Window b. Click on Soundfile tab c. Highlight the Soundbite in the Soundbite Window that you wish to edit d. Expand the horizontal graph to an appropriate resolution using the +/- e. Delete silence from the beginning of the bite (and the end, if necessary) i. Drag to highlight the portion of the waveform you wish to delete ii. When you release the mouse button, listen it will play the selected part of the waveform make sure you are not deleting any audio iii. Select Snip form the Edit menu 5. Place the soundbite on an audio track a. Create a Stereo Audio Track i. Project Add Track Stereo Audio Track (Shift+Command+S) ii. Set Input column to Built-in Audio 1-2 iii. Set Output column to Built-in Audio 1-2 b. Drag the soundbite from the Soundbite window to your track i. Place your cursor over the double ~ and the cursor becomes a hand ii. Click and drag to the stereo audio track 101

22 iii. Place the bite where you want it to be iv. Change the resolution of your time grid to place the soundbite more accurately 1. Use the -/+ in the lower right corner of the track window to change the grid resolution 2. Soundbites will lock into the grid NOTES: 102

23 DP4 DRILL 15 Recording Audio in DP4 Mono Audio Track, MOTU Audio System, Audio Monitor, Name soundbites, Delete soundbites 1. Open a new DP4 project and save it as Drill 15.x. 2. Record one group member counting from Leave a short pause between each number a. Create a new Mono Audio Track: i. Project Add Track Mono Audio Track (Shift+Command+A) ii. Set Input to: 1. Room 739 set to Mic/Guitar1 2. Room 738 set to Analog1 iii. Set Output to Built-In Audio 1-2 iv. Record enable the track b. Check your recording level i. Open the Audio Monitor (Shift+A) ii. Set your gain (on the MOTU 828) to avoid clipping 1. Remember the goal is to get the hottest signal possible WITHOUT clipping c. Record your sound d. Name your Soundbite i. In soundbite window option-click on the Soundbite Name and name it Numbers ii. Scroll over to the File Name column and option-click to give the file the same name iii. You must name BOTH the soundbite and the file e. Delete any unused soundbites i. Highlight the unwanted soundbites in the soundbite window ii. In the Mini Menu, select Delete iii. The computer will ask you if you want to delete and flush the Undo History, answer yes to all. f. Save and close your Project 3. Transfer your project to your station computer a. Make sure your Station computer in on b. On the Recording Booth computer, double-click on the hard drive to open a finder window c. Click on Network in the top left column of the finder window d. Set the view to column view e. Select the My Network folder ( Local on some computers) f. Find your station computer the name will be MIDI LAB x with x being the number of your station (01-10). g. Select your computer and click on connect h. Type your user name in for username i. Period 1 use block1 ii. Period 2 use block2 iii. Period 3 use block3 103

24 iv. Period 4 use block 4 i. Leave Password blank j. Click Connect k. Select the User folder for your period l. Click OK m. Your User folder will show up in the finder window as a server n. Click on your server and navigate to your Documents folder o. Drag the project folder from the recording booth computer to your Documents folder and drop it in to copy it. p. Be sure to copy the entire folder and all of its contents q. When copying is complete, drag the server icon from the desktop to the trash NOTES: 104

25 DP4 DRILL 16 Manipulating Digital Audio New soundfile from selection, Placing soundbites in sequence 1. Open Drill 15.x. Use Save as to save it as Drill 16.x. 2. Open the Numbers soundbites in the Waveform editor (see Drill 14) 3. Make a new soundbite for each number 1 through 10. a. Highlight the section of the waveform which represents one b. From the Mini-Menu in the Waveform editor, select New Soundfile from Selection c. A new file will appear in the Soundbites Window; change the Name and File Name to 01 d. Use Snip to trim any silence before and after the word. e. Repeat this process for each number (02, 03, 04, 10) 4. Place your edited soundbites into your Track window a. Delete any information in the Track window b. Drag and drop the mono soundbites into the mono audio track i. The files will automatically snap to the grid ii. Use the -/+ in the lower right corner of the Track window to change the resolution iii. Place a number on every beat using the following patterns: 1. Ascending Start in Descending Start in Even Start in Odd Start in

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27 DP4 DRILL 17 Introduction to Audio Effect everb, Reverb, Chorus, Delay, Echo, Pre-Amp 1. Create a new project saved as Drill 17.x in your Documents folder. 2. Go to the Music Tech web page. Navigate to the Assignments page and download the zip file Drill 17 Audio. a. Use Safari b. Control-click or Right click on the link and select Download Linked File c. After file finishes downloading, go to the desktop and double-click on the zip file to unzip it this will create a folder that will contain the audio files for this drill. 3. Import the audio files from the downloaded folder into your DP4 project. a. In the Soundbites window, select Import Audio from the mini menu, or click on the I in the Soundbite window menu bar b. Navigate to the downloaded folder and select all of the audio files c. Click Open to import. 4. Apply Echo to the soundbite Trumpet. a. Open the soundbite Bass in the waveform editor i. Highlight the soundbite in the soundbite window ii. Click Open Waveform Editor button on control panel b. Select the entire waveform c. Open Echo audio effect Audio Audio Plug-Ins Echo d. Experiment with the settings to get a sound you like i. Click Preview to hear your changes before you apply e. Click apply to save and re-write the sound file Use the procedure from #4 to apply more effects: 5. Apply Pre-Amp to the soundbite Guitar a. Experiment first with Coloration and then try EQ and Compression 6. Apply Chorus to the soundbite Bass 7. Apply Delay to the soundbite Tenor Sax 8. Apply Reverb or everb to the soundbite Alto Sax 9. Using either the Trumpet or Alto Sax soundbite, apply several of the effects to see what you can create, e.g. add chorus and reverb to Trumpet; or add delay and reverb to Alto Sax 107

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