Adam Diel

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

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

playing

All sound that the human ear hears is an analog signalA continuous electrical signal

In order for the computer to do anything with it, it must be digitized. Converted to 1’s and 0’s

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)

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

Audio is sampled at every dash on the

graph

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.

Each Line Represents One Bit of Data

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.

Dynamic Range

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

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

WahWahClipping

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 Medium

High

Can be divided up into three categories Uncompressed LossLess Lossy formats

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)

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.

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.

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.

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.

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

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

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.