• Convert changes in air pressure into electrical
• A microphone is a transducer (converts form
• Electrical voltages are “analog.”
States of Sound
• Acoustic (Sound Waves)
• Analog (Electrical Voltages)
• Digital (Numerical Values)
• Acoustic Analog Digital (and back again)
– Analog to Digital Converters
– Work with audio in a non-linear way on computer,
– Send it back out through cables to speakers into
sound waves into air and into ears, etc.
• Number of samples per second (also
expressed in Hz)
– 8,000 Hz – Telephone, Walkie-Talkies
– 44,100 Hz – Audio CD
– 48,000 Hz – DVD
– 96,000 Hz – HD, Blue Ray Discs
– 192,000 Hz – Highest currently available
• Dynamic Range: available range of volume
between the loudest and the softest audible
• Signal to Noise Ratio: the difference in volume
between what you want to hear (signal) and
what you don’t want to hear (noise).
• Dictates the number of discrete volume levels
that create the dynamic range available in
Sample Rate and Bit-Depth
• Camera Analogy: Sample rate is how many
pictures you take in a second, bit-depth is the
number of colors your camera can discern.
• Higher of each gives you better quality but
also gives you larger file sizes.
• Visual representation of digital audio file.
Digitized audio files in Pro Tools