1. Adam Diel

2.  In 1981 IBM PC 150 introduced the first PC Speaker.  Each game had to write support for it (sound cards were impractical during this time)  Could only play one square wave at a time

3.  It wasn’t until 1988 the first sound card came to the market.  Introduced by Creative Labs  Created ability to have multiple channels playing

4.  All sound that the human ear hears is an analog signal  A continuous electrical signal  In order for the computer to do anything with it, it must be digitized.  Converted to 1’s and 0’s

6.  DAC = Digital to Analog Converter  ADC = Analog to Digital Converter  The soundcard of a computer (integrated into the motherboard or an extra peripheral) will be both the DAC and ADC for the computer.  DAC for input (using a microphone for skype)  ADC for output (playing music on speakers)

7.  Sample Rate = The number of times your audio is measured per second.  The standard for CDs is 44.1 kHz (44,100 slices/sec)  The higher the sample rate the better the quality

8. Audio is sampled at every dash on the graph

9.  Bit Depth = Also known as the resolution of the file, this is how many bits you have to capture audio  Think of it as a series of levels that audio can be sliced into at any given moment in time.  Bit Rate = How much data per second is required to transmit the file.  How big the file actually is.  Usually used to measure quality in lossy formats.

10. Each Line Represents One Bit of Data

11.  Dynamic Range = Largest amplitude the sound file can contain without distortion.  Think of this as the highest/lowest level on the sound wave from the bit depth.

12. Dynamic Range

13.  Noise = Unwanted noise on an audio track  Also known as white noise  Could be a number of things, bad shielding, poor DAC or ADC, power supply, etc. Without Noise With Noise

14.  Distortion = alteration of the original shape (or other characteristic) of a sound wave.  This could be done on purpose  Electric Guitar Player’s have distortion pedals  Special effects like echo’s  Clipping = A form of distortion that occurs when an amplifier/speaker is overdriven WahWah Clipping

15.  General misconception of “if it’s good enough for CD it’s good enough for me.”  Much of the audio quality is lost. People don’t realize what they are missing. Low MediumHigh

16.  Can be divided up into three categories  Uncompressed  LossLess  Lossy formats

17.  These are WAV (windows) or AIFF (mac) files that are considered ‘lossless’ files.  Roughly 10MB per minute  The initial recording of sound is usually done in this format before being compressed down.  CDs (not MP3 CDs) are uncompressed sound files.  It’s why you can only get 80 minutes vs 700 MB (roughly 700 minutes of mp3)

18.  FLAC (Free Lossless Audio Codec), Apple Lossless Audio Codec, and Monkey’s Audio codec are all examples of this.  Roughly 5MB/Minute  These are specifically designed for Audio files and lets you convert back to uncompressed formats.  These formats are ideal for the audiophile with great sound setup.

19.  The most common formats used today, Mp3, AAC, & WMA (Windows Media Audio)  Roughly 1 MB/Minute.  Quality of these files can be referenced by the bit rate of the file. The higher the bit rate, the more that was preserved in the compression.  Also means a larger file size.

20.  The reason why Lossy formats are so popular is the amount of space uncompressed sound files can take up versus compressed files.  Back when storage wasn’t as cheap this was a huge benefit to home users.

22.  Has four basic components  Analog-to-digital converter  Digital-to-analog converter  ISA, PCI, PCIe interface to connect to the motherboard  Unless integrated  Input/Output Connections for microphones, speakers, etc.

23.  The ADC will translate analog waves into digital data.  The DAC will reverse the process of the ADC to reproduce the original analog signal.  Rather then having separate ADCs and DACs, soundcards will often integrate these into a single chip called a CODEC

24.  1/8 Inch (Most Common)  The standard headphone jack  Can only handle two channels  Optical  Very small connection, digital connection  Coaxial SDPIF (Sony/Philips Digital Interface)  Using the RCA connect, digital connection

26.  Two popular connects used in computers today  AC’97 – Created by Intel in 1997  HD Audio – Also created by Intel in 2004  These are generally used for internal CD drives  Most modern motherboards have connects for both.  HD Audio is able to support 32-bit sampling resolution  Most hardware manufactures don’t support this yet.