1. Computer Engineering and Networks, College of Engineering, Majmaah University Mohammed Saleem Bhat m.bhat@mu.edu.sa CEN-444 Networks Structure And Protocols SOUND

2. Computer Engineering and Networks, College of Engineering, Majmaah University Overview Introduction to sound. Multimedia system sound. Digital audio. MIDI audio. Audio file formats.

3. Computer Engineering and Networks, College of Engineering, Majmaah University Overview MIDI versus digital audio. Adding sound to multimedia project. Professional sound. Production tips.

4. Computer Engineering and Networks, College of Engineering, Majmaah University Power of Sound Vibrations in the air create waves of pressure that are perceived as sound. Sound waves vary in sound pressure level (amplitude) and in frequency or pitch. ‘Acoustics’ is the branch of physics that studies sound. Sound pressure levels (loudness or volume) are measured in decibels (dB). Humans hear sound over a very broad range (see p. 91)

5. Computer Engineering and Networks, College of Engineering, Majmaah University Sound Sound is energy, caused by molecules vibrating Too much volume can permanently damage your ears and hearing The perception of loudness depend on the frequency or pitch Harmonics cause the same note played on a cello to sound different from one played on a piano.

6. Computer Engineering and Networks, College of Engineering, Majmaah University Using Sound in Multimedia You need to know –How to make sounds –How to record and edit sounds on the computer –How to incorporate sounds into your multimedia project

7. Computer Engineering and Networks, College of Engineering, Majmaah University Multimedia System Sounds System sounds are assigned to various system events such as startup and warnings, among others. Macintosh provides several system sound options such as glass, indigo, laugh. In Windows, available system sounds include start.wav, chimes.wav, and chord.wav. Multimedia sound is either digitally recorded audio or MIDI (Musical Instrumental Digital Interface) music.

8. Computer Engineering and Networks, College of Engineering, Majmaah University Multimedia System Sounds Most computers have sounds ready to use

9. Computer Engineering and Networks, College of Engineering, Majmaah University Multimedia System Sounds Mac and Windows have built in sound recorders

10. Computer Engineering and Networks, College of Engineering, Majmaah University Multimedia System Sounds Windows system sounds are.WAV files in the Windows\Media directory MS Office includes additional sounds You can add your own sounds by including them in the Windows\Media directory and selecting them from the Sound Control Panel

11. Computer Engineering and Networks, College of Engineering, Majmaah University MIDI Audio MIDI is a series of musical instructions Click to play

12. Computer Engineering and Networks, College of Engineering, Majmaah University MIDI vs. Digital Audio MIDI ( Musical Instrument Digital Interface) is a communications standard developed in the 1980’s for electronic instruments and computers. It allows instruments from different manufacturers to communicate.

13. Computer Engineering and Networks, College of Engineering, Majmaah University MIDI vs. Digital Audio MIDI data is NOT digitized sound- it is music stored in numeric format Digital audio is a recording, which depend on your sound system MIDI is a score and depends on both the quality of the instruments and the sound system Quality depends on end user’s device rather than on the MIDI device and is device dependent.

14. Computer Engineering and Networks, College of Engineering, Majmaah University Making MIDI Audio Creating a MIDI score requires: –Knowledge of music and some talent –Ability to play a musical instrument –Sequencer software –Sound synthesizer Built into PC board Add-on for MAC MIDI can synthesize over 100 instruments

15. Computer Engineering and Networks, College of Engineering, Majmaah University Making MIDI Audio You will need: Sequencer Software (Smart Score) A Sound synthesizer ( built into PC sound board, an add on for MAC) MIDI keyboard or device Ability to play the piano and music theory background or a hired “expert”

16. Computer Engineering and Networks, College of Engineering, Majmaah University MIDI A MIDI file is a list of commands that are recordings of musical actions, that when sent to a MIDI player results in sound MIDI data is device dependent MIDI represents musical instruments and is not easily used to playback spoken dialog

17. Computer Engineering and Networks, College of Engineering, Majmaah University MIDI Audio MIDI is a shorthand representation of music stored in numeric form. Since they are small, MIDI files embedded in web pages load and play promptly. Length of a MIDI file can be changed without affecting the pitch of the music or degrading audio quality. Working with MIDI requires knowledge of music theory.

18. Computer Engineering and Networks, College of Engineering, Majmaah University Digital Audio Digital audio is a representation of the original sound Sampling rate is measured in kilohertz (kHz) Click to play

19. Computer Engineering and Networks, College of Engineering, Majmaah University Digital Audio Digital audio represents a sound stored in thousands of numbers or samples. Digital data represents the loudness at discrete slices of time. It is NOT device dependent and should sound the same each time it is played It is used for music CD’s

20. Computer Engineering and Networks, College of Engineering, Majmaah University Digital Audio The three sampling frequencies most often used in multimedia are CD-quality 44.1 kHz, 22.05 kHz and 11.025 kHz. The number of bits used to describe the amplitude of sound wave when sampled, determines the sample size. Digital audio is device independent. The value of each sample is rounded off to the nearest integer (quantization).

21. Computer Engineering and Networks, College of Engineering, Majmaah University Preparing Digital Audio Balance file size versus quality Set recording levels Edit the recording

22. Computer Engineering and Networks, College of Engineering, Majmaah University Preparing Digital Audio Balance file size versus quality  To calculate file size in bytes: Mono: sampling rate  duration of recording in seconds  (bit resolution  8)  1 Stereo: sampling rate  duration of recording in seconds  (bit resolution  8)  2

23. Computer Engineering and Networks, College of Engineering, Majmaah University Digital Audio Editing Once a recording had been completed, it almost always needs to be edited. Basic sound editing operations include: trimming, splicing and assembly, volume adjustments and working on multiple tracks.

24. Computer Engineering and Networks, College of Engineering, Majmaah University Digital Audio Editing Additional available sound editing operations include format conversion, resampling or downsampling, fade-ins and fade-outs, equalization, time stretching, digital signal processing, and reversing sounds.

25. Computer Engineering and Networks, College of Engineering, Majmaah University MIDI vs. Digital Audio MIDI data and digital audio are like vector and bitmapped graphics: Digital audio like bitmapped image – samples original to create a copy MIDI – like vector graphic- stores numeric data to recreate sound

26. Computer Engineering and Networks, College of Engineering, Majmaah University MIDI vs. Digital Audio MIDI data is device dependent; digital audio is not MIDI sounds (like vector graphics) are different on different devices; Digital sounds are identical even on different computers or devices.

27. Computer Engineering and Networks, College of Engineering, Majmaah University MIDI Advantages MIDI file are much more compact and take up less memory and system resources MIDI files embedded in web pages load and play much faster than digital You can change the length of a MIDI file by varying its tempo With high quality MIDI devices, MIDI files may actually sound better than digital

28. Computer Engineering and Networks, College of Engineering, Majmaah University MIDI Disadvantages MIDI represents musical instruments not sounds and will be accurate only if your playback device is identical to the production device MIDI sound is inconsistent MIDI cannot be easily used to reproduce speech

29. Computer Engineering and Networks, College of Engineering, Majmaah University Digital Audio Advantages Digital audio sound is consistent and device independent A wide selection of software support is available for both MAC and PC A knowledge of music theory is not required for creating digital audio, but usually is needed for MIDI production

30. Computer Engineering and Networks, College of Engineering, Majmaah University Choose MIDI data If you don’t have enough RAM memory, or bandwidth for digital audio If you have a high quality sound source If you have complete control over the playback hardware If you don’t need spoken dialog

31. Computer Engineering and Networks, College of Engineering, Majmaah University Choose Digital Audio If you don’t have control over the playback hardware If you have the computing resources and bandwidth to handle the larger digital files If you need spoken dialog

32. Computer Engineering and Networks, College of Engineering, Majmaah University Digital Audio You can digitize sound from a microphone, synthesizer, tape recording TV broadcast, or CD’s. Digitized sound is sampled every nth of a second. The more often you take the sample, the better the sound. Sample sizes are either 8 or 16 bits and common frequencies are11.025, 22.05, and 44.1 kHz (See pp. 209- 211)

33. Computer Engineering and Networks, College of Engineering, Majmaah University Digital Audio To prepare digital audio from analog media, record it from a device, like a tape recorder, into your computer using digitizing software. Balance the sound quality with your available RAM Set proper recording levels for a good clear recording

34. Computer Engineering and Networks, College of Engineering, Majmaah University File Size vs. Quality Audio resolution determines the accuracy with which a sound is digitized. (More bits in the sample size produces better quality and larger files) Stereo recordings are more realistic and require twice as much storage space and playback time. Mono files tend to sound “flat”

35. Computer Engineering and Networks, College of Engineering, Majmaah University Editing Digital Recordings Apple’s QuickTime Player Pro provides for primitive playback and editing Sonic Foundry’s Sound Forge is a more serious sound editor These can be used to trim, splice, volume adjustment and format conversion as well as special effects

36. Computer Engineering and Networks, College of Engineering, Majmaah University Audio File Formats A sound file’s format is a recognized methodology for organizing data bits of digitized sound into a data file. On the Macintosh, digitized sounds may be stored as data files, resources, or applications such as AIFF or AIFC. In Windows, digitized sounds are usually stored as WAV files. Both can use MIDI files (.mid)

37. Computer Engineering and Networks, College of Engineering, Majmaah University Audio File Formats CD-ROM/XA (Extended Architecture) format enabled several recording sessions to be placed on a single CD-R (recordable) disc. Linear Pulse Code Modulation is used for Red Book Audio data files on consumer-grade music CDs.

38. Computer Engineering and Networks, College of Engineering, Majmaah University Sound for the World Wide Web To play MIDI sound on the web –wait for the entire file to download and play it with a helper application –stream the file, storing it in the buffer and playing it while it downloads Streaming is dependent on the connection speed FLASH allows sound to be integrated in a multimedia presentation, controlled by buttons and saved as.mp3

39. Computer Engineering and Networks, College of Engineering, Majmaah University Adding Sound to a Multimedia Project Decide what sounds you will need and include them in the story board or cue sheet. Decide whether to use MIDI or digital audio Acquire source material (record/buy) Edit the sounds Test the sounds to be sure they are timed properly

40. Computer Engineering and Networks, College of Engineering, Majmaah University Adding sound to Multimedia CD- quality audio  Standard is ISO 10149, a.k.a. the “Red Book Standard”  Sample size is 16-bit  Sample rate is 44.1 kHz  11 seconds of audio uses 1.94 MB of space

41. Computer Engineering and Networks, College of Engineering, Majmaah University Professional Sound The Red Book Standard- ISO 10149 –( 16 bits at 44.1 kHz) allows accurate reproduction of all sounds humans can hear –Software such as Toast and CD-Creator can translate digital files from CD’s directly into a digital sound editing file or decompress.mp3 files into CD-Audio

42. Computer Engineering and Networks, College of Engineering, Majmaah University Professional Sound Compression techniques reduce space but reliability suffers. Space can be conserved by downsampling or reducing the number of sample slices taken per second. File size of digital recording (in bytes) = sampling rate X duration of recording (in secs) X (bit resolution/8) X number of tracks.

43. Computer Engineering and Networks, College of Engineering, Majmaah University Advanced Sound Management Scripting Languages such as Open Script (Toolbook), LINGO(Director), or Action Script ( FLASH) provide better control over audio playback Requires some programming knowledge

44. Computer Engineering and Networks, College of Engineering, Majmaah University Production Tips Vaughn’s Law of Minimums - there is an acceptable level of adequacy that will satisfy the audience; If your handheld microphone is good enough to satisfy you and your audience, conserve your money and energy.

45. Computer Engineering and Networks, College of Engineering, Majmaah University Production Tips Recording on inexpensive media rather than directly to disk prevents the hard disk from being overloaded with unnecessary data. The equipment and standards used for the project must be in accordance with the requirements. Sound and image synchronization must be tested at regular intervals

46. Computer Engineering and Networks, College of Engineering, Majmaah University Production Tips Audio recording - use CD’s, or VCR tapes, or DAT ( digital audio tape) tapes Create a good database to organize your sounds, noting the counter and content Testing and Evaluating- (delaying a fast machine if needed to sync with animation)

47. Computer Engineering and Networks, College of Engineering, Majmaah University Production Tips Copyright Issues Securing permission for the use of sounds and music is the same as for images Can buy royalty-free digitized sound clips DO NOT use someone’s original work without permission!

48. Computer Engineering and Networks, College of Engineering, Majmaah University Summary Vibrations in air create waves of pressure that are perceived as sound. Multimedia system sound is digitally recorded audio or MIDI (Musical Instrumental Digital Interface) music. Digital audio data is the actual representation of a sound, stored in the form of samples.

49. Computer Engineering and Networks, College of Engineering, Majmaah University Summary MIDI is a shorthand representation of music stored in numeric form. Digital audio provides consistent playback quality. MIDI files are much smaller than digitized audio. MIDI is device dependent digital audio is not MIDI files sound better than digital audio files when played on high-quality MIDI device.