IMM 110 Notes 09-26-2018

IMM 110 Notes 09-26-2018





Digital Audio/Sound





Overview of Sound

  • Changes in air pressure
  • Electrical signals that your brain interprets as sound
  • Waveforms (graphing air pressure)
  • Digital audio is the method of representing audio in digital form - converting a sound wave into numbers

    • - a process referred to as digitizing

    Loudness and Pitch

  • Amount of change = loudness/volume
  • Rate of change = pitch
  • Known as amplitude (loudness) and frequency (pitch) of the wave


    • The loudness of a sound is measured in decibels (dB). The frequency is measured in Hertz (Hz)

    Sound Cards

  • Converts analog signals to digital and vice vers


    • Inputs

    You can digitize sound from a

  • Microphone
  • Synthesizer
  • CD
  • Audiocassette (tape recordings)
  • Laserdisc
  • VCR


    • Digiizing/Sampling

  • Digitized sound is sampled sound

    • - A sample of sound is taken and stored as digital information in bits and bytes
  • Converting analog to digital

    • -Generate a series of binary 1s and 0s
  • Quality of sound determined by its sampling rate (frequency) and bit depth (sample size/resolution/dynamic range)

    • -Sample rate: how often samples are taken
    - Bit depth: how many numbers are used to represent the value of each sample

    Sampling rate/frequency

  • The number pf samples per second used to store a sound
  • Measured in kilohertz (thousands of samples per second)
    -44.1 kHZ, 22.05 kHz, 11.025 khz
  • More storage space is required when using higher sampling rates
    -More information is being stored
    -better quality


    Sample Size/Bit Depth

  • Number of bits used to represent a single sample

    • -8-bit, 16-bit, 24-bit, 32-bit
    Different resolutions

    lower bit depth is noisier

    1 byte for 8-bit samples

    2 byte for 16-bit samples

  • Higher a sound's bit depth, the higher its fidelity(sounds more like the original)


    • -Larger the sample size, the more accurately the data will describe the recorded sound

    Quality

  • The more often you take a sample and the more data you store about that sample, the finer the resolution and the quality of the captured sound when it's played back


  • 8-bit sample size provides 256 equal units to describe the dynamic range or amplitude- the level of sound at that time

  • 16-bit sample size provides 65,536 equal units to describe the dynamic range



    • Quantization

  • The value of each sample is rounded off to the nearest integer


  • If the amplitude is greater than the intervals available, clipping of the top and bottom of the wave occurs


  • Quantization can produce an unwanted background hissing noise, and clipping may severely distort the sound



    • Mono or stereo

  • Amplifiers produce monophonic sound by transmitting a single channel to one or more speakers


    • -Smaller file size

    -Suitable for speech recordings

  • Stereophonic sound uses two or more independent audio channels


    • -Sensation of a live band or orchestra

    -Larger file size

    -Suitable for music mixed with various instruments and effects


























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