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Digital Sound. Actual representation of sound Stored in form of thousands of individual numbers (called samples) Not device dependent Stored in bits. Advantages of Digital Sound. Consistent playback quality Wider selection of application software and system support for digital audio
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Digital Sound • Actual representation of sound • Stored in form of thousands of individual numbers (called samples) • Not device dependent • Stored in bits
Advantages of Digital Sound • Consistent playback quality • Wider selection of application software and system support for digital audio • No demand for music theory and musical scores
Disadvantages of Digital Sound • Does not allow for the manipulation of all details of composition • Huge files • Significant processor overhead
Sound Quality • Capture at highest possible quality • Determine by capabilities of target delivery platform
Sampling Rate • number of samples per second, measured in kilohertz (kHz) • higher sampling rate, higher sound quality
Sampling Size • size in bits used to quantify the signal • types of sample size • 8-bit • 16-bit • larger sample size, better the data describes recorded sound • larger sample size, more "steps”are represented within dynamic range of sound
Stereo Vs. Monophonic Sound • Stereo Sound • more lifelike and realistic • provides data in two different channels - left and right • files require twice as much storage space as mono files • Monophonic Sound • tend to sound "flat" and uninteresting • only one channel
Humans • Nyquist’s Therom: • Sample rate should be twicethe highest frequency • humans: • 20 Hz • 20,000 Hz
According to Nyquist • Should sample 40,000 times per second • In Reality samples 44,100 Hz
Sampling Formulas • to determine the size in bits of a digital mono recording: • sampling rate * duration of recording in seconds * (bit resolutions) * 1 • to determine the size in bytes of a digital stereo recording: • sampling rate * duration of recording in seconds * (bit resolutions) * 2
File size Sample…44,100 :listen to sound determine volume each sample Depth (sample size) is 8 or 16 Channels: 1 or 2 Map each sample to a digit
File Size vs. Quality • Higher the sound quality, the larger the file • Record at highest sampling rate and resolution, i.e., 16-bit stereo, 44.1 kHz
File Size • =sample Rate*number of channels *bits per sample* 60 seconds • =Ask class to figure size for • 10 seconds Assume stereo, 8 bit mono
Digital Sound File Formats • 1. AIF/AIFF (Macintosh) • 2. AU (Sun, NeXT) • 3. WAV (Windows)