This document discusses key concepts in capturing and working with audio digitally. It explains how sound is converted from acoustic waves to electrical voltages through microphones, then from analog voltages to digital numerical values using analog-to-digital converters. It describes common sample rates used in audio recording and formats like CDs, DVDs, how higher sample rates provide more accuracy. It also covers bit-depth and how it determines the dynamic range, and how sample rate and bit-depth together affect audio quality and file size, like with digital camera resolution. Finally, it mentions visualizing audio as waveforms and common file formats like WAV, MP3, and AAC.

1. Working with Audio
Sound and Audio Engineering

2. Capturing Audio
• Convert changes in air pressure into electrical
voltages
• A microphone is a transducer (converts form
of energy).
• Electrical voltages are “analog.”

3. 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,
etc.
– Send it back out through cables to speakers into
sound waves into air and into ears, etc.

4. Sample Rate
• 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

5. Higher sample rates = greater accuracy

6. • Dynamic Range: available range of volume
between the loudest and the softest audible
sounds.
• Signal to Noise Ratio: the difference in volume
between what you want to hear (signal) and
what you don’t want to hear (noise).

7. Bit-Depth
• Dictates the number of discrete volume levels
that create the dynamic range available in
digital audio.

8. 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.

9. Waveform
• Visual representation of digital audio file.

10. Digitized audio files in Pro Tools
(editing software)

11. Audio File Formats
• Uncompressed
– WAV
– AIFF
– SD2
• Compressed
– MP3
– AAC
– WMA