Audio Knowledge

audioFriends, I found some of my interesting old notes on ‘audio’. I feel it is worth to share with you.

  1. Audio role in Multimedia
  • Attracts your attention/shocks/excites
  • Change moods
  • Feeling as you are in dream
  • Give pleasure
  • Inform
  • Inform with style and impact

2. Audio is applied to

  • Narration
  • Dialogs, Conversation
  • Background music
  • Music mixed with narration
  • Transition effects in audio
  • Noise
  • Real/Informative sounds

3. Selection of audio for multimedia

  • Topic of multimedia presentation
  • Sound related to information
  • Objective of presentation
  • Desire effect for presentation
  • Target Audience
4. Factors which affects quality of recording
  • Breathing
  • Air conditioner noise
  • Movement
  • Suitability of recording settings
  • Input volume level
  • Consistency of settings
  • Quality of source audio
  • Quality and connectivity of cables

5. Sound Card

  • 8bit, 16bit, 32bit

6. Layout of sound card

  • Microphone connector
  • Line in Jack
  • Microphone in Jack
  • Speaker out/Line out Jack
  • Joystick/MIDI connector
  • IDE connector

1.       Audio File formats (mentioning only few)

  • AU files: (.au) are the most commonly used format format for cross-platform applications (the µ-law format, is also called AU from the file extension used for these files)
  • AIFF files: Audio Interchange file format files (.aiff, .aif, and .aifc) are widely used on Macintosh and silicon graphics computers
  • WAV files: WAV files(.wav) are used with Microsoft Windows applications
  • MP3 files: By eliminating portions of the audio file that are essentially inaudible, mp3 files are compressed roughly one-tenth of audio formats such as WAV(uncompressed)etc.
  • WMA files: Window Media Audio
  • RA files: Real audio file format designed for streaming audio over the internet
  • RIFF files: Resource Interchange File Format. Developed by Micorsoft
  • SND/Sound files : This file format was developed by Apple and is l, imited to a sampling rate of 8bits
  • MID/MIDI/MFF files: Musical Instrument Digital Interface, stores MIDI data
  • VOC files: Voice, developed for Sound Blaster card by Creative Technology. Supports sampling rates of 8 and 16 bits, with or without compression

8. Qualities of Sound

  • Nature of sound: Oscillatory movement of air particles forming directional longitudinal waves
  • Waveform: Describes measurement of speed of the sound
  • Amplitude: Relative loudness of the sound
  • Volume: The amplitude determines the sounds volume, measured in decibels. Human hearing range from 1 to 120 decibels

9. Basic Qualities of Sound

  • Valley and Crest: The lowest part of a waveform is reffered as valley and the peak point as the crest
  • Frequency: No of crests that occur in one second is the frequency also called as Pitch
  • Mono: Sound using only one channel
  • Stereo: Sound using multimedia channels. Digital stereo uses two channels namely Left and Right

10. Analog and Digital Audio

  • Analog: Continuous stream of the waveforms
  • Digital: Finite numerical combinations representing the waveform
  • Requirement of conversion: To handle the sound using computer(digital device) it needs to be converted into digital form
  • Conversion Methods: Use of ADC (Analog signals => electrical impulses => ADC => Digital Sound)

11. Benifts of Digital Sound

  • 100% reproduction
  • Easily Editable
  • Long Lasting
  • Timely Retrieval on Demand
  • Availability of Reliable Storage Media

12. Sampling/Resolution

  • Sampling: The process of digitization of the analog sound
  • Sampling rate: Number of samples per second
  • Typical rate can range from 5000 to 100000 samples per second
  • The number of bots used to store each sample is known as the resolution of the sound
audio_table

MIDI: Musical Instruments Digital Interface

  • MIDI is a simple digital protocol
  • By connecting a computer to a keyboard through a MIDI connection, music can be recorded
  • Many programs are supporting MIDI for communicating with synthesizers. MIDI files are widely used for exchanging computer music

References for content and images: Internet and multimedia books

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