A sound card, as the name suggests, is a computer component that processes sound signals and enables the computer to provide a rich audio experience. Before the sound card was invented, a computer could only make sounds in the form of beeps which could be changed depending on their frequency and depth. Early developers created music for games from these beeps by varying their pitch and duration. It was only in the 1980s that manufacturers began to introduce add-on, dedicated sound cards for computers. Computers could now provide not only multi-channel, high definition, surround sound and the ultimate 3D sound effects for gamers but computers could also record sounds from external sources with higher degree of clarity.
Anatomy of a Sound Card
The key components of a sound card are an audio processor also known as digital signal processor (DSP), an analog-to-digital converter (ADC), a digital-to-analog converter (DAC), an operational amplifier chip (op-amps) and certain ports. Some sound cards also have memory for faster processing of data.
An audio processor or a Digital Signal Processor is a microprocessor similar to a Graphic Card’s graphics processing unit (GPU). A DSP takes the load of processing the sound signals which otherwise would be processed by the CPU of the computer. This not only lightens the CPU’s load but also makes for better signal processing and hence better sound as DSPs can simultaneously process multiple sounds and/or channels. On the other hand, sound cards which do not posses their own DSP rely on CPU for processing power.
ADC and DAC
Sound in its physical (energy) form is analog and is different from computer data. Sound travels in the form of waves through a medium and the sound which falls on the eardrums is audible due to the vibrations it makes. On the other hand, a computer processes any type of data in form of digital bits (1s and 0s) and hence computers have to convert the sound into digital format to process it. A computer achieves this through the ADC and DAC components of a sound card.
An audio-to-digital converter (ADC), as the name suggests, converts the analog sound waves to digital format for the computer to process them. The ADC digitizes or samples the sound by making accurate measurements of the sound wave at frequent intervals. The number of measurements the ADC makes per second is called the sampling rate which is measured in kHz (kilohertz). A faster sampling rate denotes a more accurate reconstructed wave. Hence sound cards with higher sampling rates are preferred more.
A DAC does just the opposite by converting the digital data back into analog sound. Here also, faster sampling rates and accurate measurements mean that the reconstructed sound wave will be nearly identical to the original sound wave.
However, higher sampling can sometimes also deteriorate or reduce sound quality as the physical process of transferring sound from analog to digital through wires can cause distortion. This reduction in sound quality is measured in two factors, viz. Total Harmonic Distortion (THD), calculated as a percentage and Signal to Noise Ratio (SNR) which is measured in the unit of decibels. The smaller these both numbers, the better the quality of the sound card. Few cards also support digital input that allows users to store sounds without the need to convert them to analog format.
Operational Amplifier (op-amp)
An operational amplifier amplifies the analog sound signal in the sound card where the signal is transferred with less distortion and loss. Technically an op-amp is a device that has very high input impedance and very high gain. The higher the quality of an op-amp on a sound card, the higher the quality of the sound will be. Also, sound cards may have a single amplifier or may have an amplifier per channel.
Similar to graphic cards, sound cards, especially add-on ones, can also have their own on-board memory for faster processing of data. This can considerably increase the computer’s performance if high end cards have their own memory and hence do not bank on the computer’s RAM.
Standard memory cards have at least microphone and speaker connectivity ports. High end sound cards pack many ports depending on the standards they support. These sound cards can have ports ranging from connections (multiple) for surround sound and 3D sound, S/PDIF and MIDI to USB and FireWire ports.
Formats, Software and Drivers
Most new sound cards support the latest audio formats like the Dolby Digital Live, DTS NEO, and Dolby Pro Logic IIx etc that enhance the quality of sound and provide for an exceptional audio experience. These also mostly come with their own software and drivers to fully bank on the card’s capability.
Sound cards for computer come chiefly in two formats, namely, integrated and add-on. Most motherboards and laptops these days have integrated sound cards that are sufficient for personal entertainment; however they are not as powerful as their add-on counterparts. Audiophiles and gamers usually want more detailed sound and can hence opt for add-on sound cards for greater audio experience. Add-on cards are available in quite a few connectivity standards ranging from PCIe connectivity to FireWire connectivity depending on the need.
For a complete and exceptional audio experience one also needs a good and compatible speaker system because no matter how high performing a sound card is, it cannot compensate for bad or underperforming speakers.