Skills: Set sample size and rate in Audacity Concepts: analog versus digital data, analog to digital conversion, digital to analog conversion, sample rate, sample size, quality-file size trade off This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License. Recording and encoding analog data
Where does this topic fit? Internet concepts – Applications – Technology – Implications Internet skills – Application development – Content creation – User skills
Analog data But, computers require digital data …
Which clock is digital? Analog?
A digital clock … 01.49
Analog to digital converter Digital to analog converter Recording and playing sound Computer (150) (201) (199) … Computer (150) (201) (199) …
Analog to digital converter Digital to analog converter Reading and adjusting temperature Computer (150) (201) (199) … Computer (150) (201) (199) …
Sensors for all sorts of things Speed Rate of flow Pressure Altitude Acceleration Motion Rotation Temperature Light level Sound Compass direction Blood pressure Heart rate And more … The Internet of things
Sampling an analog signal How can we improve the fit of the digital curve? (Hint: 2 ways)
1. Increase the sampling rate What is the second thing we can increase? Hint: how did we increase the variety of colors in images or symbols in text?
2. Increase the sample size (more bits per sample)
Increase sample rate → quality ↑ file size ↑ Increase sample size → quality ↑ file size ↑ Recording tradeoffs
00A 01B 10C 11D Text 2-bits/character Image 1-bit/pixel Sound 2-bits/sample Increase code bits → quality ↑ file size ↑
Edit > Preferences > Quality Set default sample rate and size
Set sample rate and size
AnalogDigital What other real world phenomena can we sample and input to a computer?
Summary
Self-study questions At a sampling rate of 8, bit mono samples per second, what would be the file size for a one minute recording? How much larger would a stereo recording be? How much larger would the file size be if we were to sample at 48,000 samples per second? How much larger would the file size be if the samples were 32 bits each?
Resources Wikipedia analog: Wikipedia digital: A more detailed tutorial: