1. Technology
ICT
Option: Audio

2. Digital Audio Sound is represented as Analogue Waves
Sound must be converted to a Digital Form to be processed by a computer
Sampling rate
Analogue signal
Time
Amplitude

3. Digital Audio Sound wave is measured at regular intervals
Process is called Sampling
Number of samples /second is the Sampling Rate
Sampling rate
Analogue signal
Time
Amplitude

4. Recording Digital Audio
Audio can be recorded into a computer using:
External microphone
External player - tape or record player
Internal player - CD or DVD Rom drive
Microphone (Pink)
Speakers(Green)
External Player (Blue)
External ports:

5. Recording Digital Audio
When the recorded sound reaches the computer’s Sound Card, an ADC (analogue to digital convertor) converts the sound to digital values. The number of values taken is set by the sampling rate.

6. Recording Digital Audio
Factors affecting the recording quality:
Sampling rate - samples taken per second (Hz). Audio CD is recorded at 44KHz - software default
Sample format - number of bits representing each sample , 24 or 32bits
Compression - sophisticated methods used by software to reduce file size

7. Recording Digital Software
A number of software applications are available for sound recording and editing:
Adobe Audition
Steinberg Wave Lab
Sony Sound Forge
Apple Final Cut
Creative Wave Studio
Audacity

8. Audacity
Audacity is a free to use multi-track digital audio application. It is a fully featured cross-platform editor, mixer and recorder. It is available for download at:

9. File Formats
Audio tracks can be imported into audacity in almost all file formats. Files can be saved in the following formats:
Audacity project format (aup) - Audacity default. Opens and closes files very quickly. Incompatible with all other audio software. Used during project creation (multi-track). Finished project is then saved to another file format.

10. File Formats
Windows wave format (wav) - Windows default. An uncompressed format.
Audio interchange file format (aif) - Apple MAC default. It is also uncompressed.
 MPEG3 (mp3) - uses compression (up to 10:1). Audacity can import MP3, but a plug-in is necessary to export MP3.
Ogg Vorbis (ogg) - Alternative to MP3. Similar compression - better quality. Patent free.

11. Audacity Interface Selection Toolbar Track Window Edit Toolbar
Control Toolbar
Meter Toolbar
Mixer Toolbar

12. Opening Sound Files
When Audacity is opened, the work area is empty. Audio files can be opened in audacity in the following ways:
File menu, Open - for single track editing
Project menu, Import - for multi-track editing

13. Toolbars File Menu File menu - open and save projects
Edit menu - select and edit audio tracks
View menu - zoom controls
Project menu - add tracks to a project
Generate menu - generate noise, silence
Effects menu - add fade, remove noise and clicks etc.
Analyse menu - advanced tools - find the beat etc.

14. Control Toolbar Control Toolbar
The control toolbar is divided into two sections:
Editing tools - zoom, select and edit tracks:
Audio control tools - control the recording and playing of audio tracks or projects
Editing tools
Audio control tools

15. Edit Tools Selecting tool - select a track/portion of a track.
The selection tool is used to select a portion at the end of the Tank.wav waveform. The Fade Out command - Effects menu is used and the result is seen below. Instead of a sudden end to the sound, it will fade to silence over the selected time.

16. Edit Tools
Draw tool - The draw tool is used for modifying individual samples within the waveform. The waveform must be zoomed sufficiently to see the samples as dots along the profile.
Below, the Tank.wav track is zoomed to show individual samples. The samples can be dragged to new positions as shown below.
Samples

17. Edit Tools
Envelope tool - used to change the volume of a waveform or a selection from a waveform.
When the tool is chosen, blue lines appear above and below the waveform. By clicking the blue line at points, the waveform amplitude can be increased or decreased. with the corresponding reduction or increase in volume.

18. Edit Tools
Time shift tool - used in multi track mode to move tracks relative to each other.
Move the cursor to the beginning or end of the track and the cursor changes to the double-arrow to indicate time shift. Drag the track to the required position relative to the other track(s).

19. Edit Tools
Zoom tool - used to zoom in and out of a waveform. The left mouse button zooms in and the right mouse button zooms out. Zooming if necessary when editing a waveform.
Multi tool - gives access to the other five editing tools automatically depending on the location of the cursor:
Move the cursor over the ruler and it changes to the zoom tool
Move the cursor to the beginning or end of the waveform and it changes to the time shift tool
Move the cursor over the waveform and it changes to the selection tool etc.

20. Audio Control Tools
Skip to start - moves the cursor to the beginning of the project.
Skip to End - moves the cursor to the end of the last track
Play - plays the project from the current cursor position. Shift + Play loops (continuously plays) the
Record - starts recording a track from the current cursor position
Pause - temporarily stops recording or playback.
Stop - stops recording or playback

21. Mixer Toolbar The mixer toolbar has three controls:
The playback volume is the volume is used by the system to play the audio file
The recording volume is the volume at which the audio track is recorded
Playback volume
Input source
Recording volume

22. Mixer Toolbar
The input source drop down menu is used to select the device used for recording:
Microphone - a microphone connected to the pink jack
Line in - an external device connected to the blue jack
Stereo mix - anything played through the sound card in stereo
Mono mix - as above, only in mono

23. Edit Toolbar
The edit toolbar is a shortcut toolbar and is used to perform edits on a selected waveform of part of a waveform.
Cut - removes the selected waveform or part of to the clipboard
Copy - copies the selected waveform or part of to the clipboard
Paste - pasts the contents of the clipboard at the current cursor position
Trim - removes the area outside the current selection
Silence - adds silence to the current selection
Undo/Redo - as in any application
Zoom - plus, minus, fit selection in window and fit project in window

24. Meter Toolbar The meter toolbar monitors the input and output levels.
Playback meter is green, recording meter is red
L and R meters are for the left and right channels
Light areas show average levels, darker areas show peak levels
Peak lines to the right show the max level in the previous three seconds
Red lines at the extreme right show only if clipping is detected. Clipping is where the audio is too loud and distortion has occurred. Recording should be stopped and re-recorded at a lower level

25. Track Menu
Each track in a multi-track project will have a track drop-down menu. The menu shows a series of commands that effect only the individual track. The commands include:
Name - name or rename the track
Move track - move the track up or down the project
Mono - convert a stereo track to mono
Left channel - use the left speaker only
Right channel - use the right speaker only
Make stereo - joins two tracks into a stereo track
Split track - stereo track split into two mono tracks
Set format , 24 and 32 bit format
Set rate - number of samples per second for

26. Selection Toolbar The status area shows: The current tool selected
The current tool selected
The current sampling rate
The current selection
Snap condition

27. Preferences
Preferences are found in the Edit menu. There is an extensive range of preferences, but only a few need be set.
Quality tab - Sampling rate and the Sampling format are set

28. Preferences
Audio I/O tab - the Recording and Playback devices ca be set. These should be set to the system Sound Card in each case. The number of channels used to record is also set here. This will be mono or stereo.