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Digital Audio. A/D and D/A. A/D=analog to digital conversion. Turing vibration into binary code (mic to recorder or DAW) Conversion of continuous signal to a discrete one Continuity to discrete steps - PowerPoint PPT Presentation
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Digital Audio
A/D and D/A
• A/D=analog to digital conversion. Turing vibration into binary code (mic to recorder or DAW)
– Conversion of continuous signal to a discrete one
– Continuity to discrete steps
• D/A=digital to analog conversion. Turn code into vibration (DAW or recorder to monitors (headphone and speaker))
• Most recording devices (computer or recorder) have both devices
Sampling Rate• Measured in KHz
– 32KHz, 44.1KHz, 48KHz, 96KHz, 192KHz
– How many times per second a waveform is “analyzed”
• Measures amplitude over time
• Higher the sampling rate the more accurately the sound is reproduced digitally
• Higher the sampling rate, more processing in post
• Essentially, it deals w/ the highest reproducible frequency
• Represented horizontally in digital waveform
Nyquist Theorem
• In order to reproduce a sound waveform as a digital waveform, the sampling rate must be at least TWICE frequency of of the sound being captured
• Human hearing range???... 20KHz
• Aliasing=new frequencies appear and distort original signal
• Image aliasing...resolution
Bit Depth
• Aka “quantization”
– How amplitude is represented as binary code
• Determines the dynamic range
– Can capture quieter sounds, louder sounds, and sound with less noise
• 1 bit = +6dB of dynamic range
– 16 bit resolution= 16 x 6= 96dB of dynamic range
• Represented vertically in digital waveform
Sampling Rate + Bit Depth
• More/less information
• Allows for more/less processing
• More/less dynamic range
• More/less disk space
• More/less accurate digital representation
• DVD Audio/Blur-ray=96KHz 24 bit
• Broadcast audio=48.1KHz 16bit
• CD audio=44.1KHz 16 bit
Sampling Rate + Bit Depth Cont'd
• Bit depth + sampling rate + time = file size
• 96KHz is 200% larger than 48KHz
• 24bit is 300% larger than 16bit
Formats
• MP3...NEVER EVER EVER USE THIS!
– Compressed to 1/10 the size of a .WAV or .AIFF
– Made for sharing
– Don't record EVER in this format
– Use format for sharing larger files
• .WAV = Microsoft's proprietary format
• .AIFF = Apple's proprietary format
• WAV/AIFF are “lossless audio”