Audio in multimedia Systems Lecture Notes.pptx

Audio in multimedia

1. Audio in Multimedia

2. Sound is perhaps the most important element of multimedia. It is meaningful “speech” in any language, from a whisper to a scream. It can provide the listening pleasure of music, the startling accent of special effects or the ambience of a moodsetting background. Sound is the terminology used in the analog form, and the digitized form of sound is called as audio.

3. The power of Sound  pressure. These waves spread like the ripples from a pebble tossed in a still pool. And when they reach your eardrums, you experience the changes of pressure, or vibrations, as sound.  Acoustics is the branch of physics that studies sound. Sound pressure levels are measured in decibels ( db ).

4. 3.3 Multimedia Sound Systems The multimedia application user can use sound right off the bat on both the Macintosh and on a multimedia PC running Windows because beeps and warning sounds are available as soon as the operating system is installed.

5. On the Macintosh you can choose one of the several sounds for the system alert. In Windows system sounds are WAV files and they reside in the windows\Media subdirectory. There are still more choices of audio if Microsoft Office is installed. Windows makes use of WAV files as the default file format for audio and Macintosh systems use SND as default file format for audio.

6. 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.

7. 3.4 Digital Audio Digital audio is created when a sound wave is converted into numbers – a process referred to as digitizing. It is possible to digitize sound from a microphone, a synthesizer, existing tape recordings, live radio and television broadcasts, and popular CDs. You candigitize sounds from a natural source or prerecorded.

8. Digitized sound is sampled sound. Ever n th fraction of a second, a sample of sound is taken and stored as digital information in bits and bytes. The quality of this digital recording depends upon how often the samples are taken.

9. 1. Introduction to Audio in Multimedia What is Audio in Multimedia? Audio refers to any sound content used in a multimedia context, including music, sound effects, dialogue, and voiceover.

10. Role of Audio in Enhancing Multimedia Audio adds depth and emotion. Audio creates atmosphere and helps direct the user's attention. Sound can guide users through navigation (e.g., auditory cues in UI).

11. Types of Audio in Multimedia Voiceovers: Used in narrations or descriptions. Background Music: Adds mood and tone to multimedia content. Sound Effects (SFX): Enhances the experience with realistic sounds. Ambient Sound: Environmental audio that creates immersion.

12. BASICS OF SOUND AND DIGITAL AUDIO A. Sound Waves and Properties What is Sound? Sound is a vibration that propagates through air (or other mediums) and is perceived by human ears.

13. Key Properties of Sound:   Amplitude: Relates to the loudness (volume) of the sound. Higher amplitude = louder sound.

14. Frequency: Measured in Hertz (Hz), refers to the number of vibrations per second. Determines the pitch of the sound. Low frequency = low pitch (e.g., bass sounds). High frequency = high pitch (e.g., treble sounds).

15. Timbre : The quality or color of the sound. Helps distinguish different sound sources. Waveform: The shape of the sound wave, which represents the change in air pressure over time.

16. B. Digital Sound: Sampling and Quantization Analog vs. Digital Sound: Analog sound is continuous, whereas digital sound is represented as discrete numerical values. Sampling: The process of capturing sections of an analog signal at regular intervals. Sampling Rate: The number of samples per second, measured in Hertz (Hz). Common rates: 44.1 kHz (CD quality), 48 kHz (professional audio), 96 kHz (high-fidelity audio).

17. Quantization: After sampling, quantization converts the amplitude of each sample into a digital value (bit depth).   Bit Depth: Determines the resolution of the sound (e.g., 16-bit, 24-bit). Higher bit depth = more accurate sound reproduction. Nyquist Theorem: The sampling rate must be at least twice the highest frequency of the sound to avoid aliasing.

18. 3. Audio Formats and Compression A. Lossless vs. Lossy Compression Lossless Compression: Preserves the original sound quality by compressing data without losing any information. Formats: FLAC, ALAC, WAV. Suitable for high-fidelity audio requirements but results in larger file sizes.

19. Lossy Compression: Reduces file size by discarding some audio information that is less noticeable to human ears. Formats: MP3, AAC, OGG. Sacrifices some quality for smaller file sizes, making it ideal for streaming and online applications.

20. B. Common Audio File Formats WAV: Uncompressed format, commonly used for high-quality audio. MP3: Most popular lossy format, widely used due to its small file size and acceptable quality. FLAC: Lossless format, provides high-quality audio at a compressed file size. AAC: Advanced lossy format, used in platforms like iTunes and YouTube. OGG Vorbis: Open-source lossy format, used in some games and online media.

21. 4. Audio Editing Techniques A. Tools for Editing Audio Audacity: Free, open-source tool. Adobe Audition: Professional audio editing software. GarageBand: Mac-based audio editor. Avid Pro Tools: Industry-standard for professional music production.

22. Basic Editing Techniques Trimming and Cutting: Removing unwanted parts from the audio track. Fading In and Out: Gradual increase (fade-in) or decrease (fade-out) of volume at the start or end of an audio clip.

23. Normalization: Ensuring that the audio's loudness is uniform throughout the track. Noise Reduction: Reducing background noise in an audio recording. Equalization (EQ): Adjusting the balance between different frequency components. Compression: Reducing the dynamic range between the loudest and quietest parts of the audio.

24. 5. Multimedia Applications of Audio A. Voiceovers Used in tutorials, instructional videos, podcasts, and advertisements. Tips: Use high-quality microphones, ensure clarity and consistent volume.

25. B. Sound Effects (SFX) Enhances user engagement, especially in films, games, and interactive applications. Tips: Use libraries for pre-recorded SFX or record custom sounds. C. Background Music Sets the emotional tone for multimedia projects. Tips: Ensure music does not overpower dialogue or other sounds.

26. D. Audio in Games Dynamic audio based on user interactions. Importance of real-time sound generation and spatial audio for immersive experiences. E. Audio in Websites Background music, sound feedback, voice assistants. Accessibility considerations for web audio (e.g., providing captions or alternatives).

27. 6. Audio for Accessibility Importance of Accessible Audio: Ensuring that multimedia is accessible to all users, including those with hearing impairments. Common Practices: Closed Captions : Provide text for spoken dialogue and relevant sounds. Transcripts: Written versions of audio content.

28. Audio Descriptions : Narrating visual elements of a multimedia project for the visually impaired. Volume Controls: Allow users to adjust audio levels based on their needs. Sign Language Interpretation: For multimedia content like videos.

29. 7. Best Practices for Audio in Multimedia Balancing Audio Elements : Ensure music, voice, and effects do not overlap or interfere with each other. Choosing Appropriate Audio Formats: Select formats based on the platform and required quality.

30. Consideration for Mobile Platforms : Optimize file sizes and ensure that audio sounds good on smaller speakers. Avoid Overuse of Sound Effects: Too many effects can overwhelm the user and dilute the message. Testing Across Devices : Check how the audio sounds on different speakers and devices (e.g., headphones, phone speakers).

31. 8. Conclusion Recap of key points: Audio enhances the multimedia experience. Understanding sound properties, digital audio, and formats is essential. Editing techniques allow for fine-tuning sound. Applications of audio are diverse, from games to accessibility. Best practices ensure quality and accessibility.