Digital Sound l Actual representation of sound l

Digital Sound l Actual representation of sound l Stored in form of thousands of individual numbers (called samples) l Not device dependent l Stored in bits

Advantages of Digital Sound l Consistent playback quality l Wider selection of application software and system support for digital audio l No demand for music theory and musical scores

Disadvantages of Digital Sound l Does not allow for the manipulation of all details of composition l Huge files l Significant processor overhead

Sound Quality l Capture at highest possible quality l Determine by capabilities of target delivery platform

Sampling Rate l number of samples per second, measured in kilohertz (k. Hz) – higher sampling rate, higher sound quality

Sampling Size size in bits used to quantify the signal l types of sample size – 8 -bit – 16 -bit – larger sample size, better the data describes recorded sound l larger sample size, more "steps”are represented within dynamic range of sound l

Stereo Vs. Monophonic Sound l 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 l Monophonic Sound – tend to sound "flat" and uninteresting – only one channel

Humans l Nyquist’s Therom: l Sample rate should be twice the highest frequency l humans: – 20 Hz – 20, 000 Hz

According to Nyquist l Should sample 40, 000 times per second l In Reality samples 44, 100 Hz

Sampling Formulas l to determine the size in bits of a digital mono recording: – sampling rate * duration of recording in seconds * (bit resolutions) * 1 l 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 l Higher the sound quality, the larger the file l Record at highest sampling rate and resolution, i. e. , 16 -bit stereo, 44. 1 k. Hz

File Size l =sample Rate*number of channels *bits per sample* 60 seconds l =Ask class to figure size for l 10 seconds Assume stereo, 8 bit mono

Digital Sound File Formats l 1. AIF/AIFF (Macintosh) l 2. AU (Sun, Ne. XT) l 3. WAV (Windows)