Copyright Michael Karbo, Denmark, Europe.
Chapter 11. About computer sound
In the first part, we have looked at sound and sound reproduction generally (analog and digital). In this part we are going to take a closer look into the computer’s sound system. We are also going to look closer at the mp3 format, which is closely connected with the computer, but which can be used for many other purposes. Finally, I will touch on the MIDI system, which can, among other things, be used for composing music on a computer.
There are by now sound cards in most computers; sometimes they are used a lot and sometimes not at all. In this section, we are going to look at the sound card in a little more overall and maybe theoretical perspective; later the examination will be more practical.
A sound card can be, in fact, be described as a controller function. There are a lot of controllers in a computer. The main controller is the CPU, which controls the whole of the superior continuity and keeps the rest of the other components together. On the outskirts of the computer’s architecture, we find the more specialised controllers, which control single components such as hard disks and other drives, the network, the screen and the keyboard. If the CPU is the ”king”, then these controllers are really small ”generals”, who rule absolutely in their own little limited realms.
A sound card is one of these local controllers, whose job it is to control everything, which has to do with the transmission of sound (analog and digital) in and out of the computer:
Figure 57. The sound card is a controller, which handles everything, which has to do with sound and sound data.
This controller architecture means, that a sound card in the eyes of the computer is a limited and standardised system. Windows is, in fact, designed to work with a computer architecture, which is divided, into clearly limited and well-defined substructures. These standardised devices are recognised by the control system and other programs, which understand how to use them.
If you look at the system devices in Windows, sound devices are grouped under the category ”Devices for sound, video and games”. In Figure 58 a Sound Blaster Audigy sound card is installed, can you see it?
Figure 58. All sound devices are clearly defined in Windows.
Several kinds of sound functions
The sound card itself is found in several ”designs”, which are selected according to price and quality:
There is no doubt that the last solution with a separate sound card is the right one, if you want to work with sound in your computer.
The absolutely cheapest sound is obtained with an AC’97 standard. The motherboard’s so-called chip set is already a collection of controllers and it quite easy to increase it with a simple sound function from an AC’97 specification. A/D- and D/A converting is carried out here in a little cheap codec chip, which is installed on the motherboard and connected to the chip set.
An AC’97 is not a real sound card, so the computer’s main processor (the CPU) is burdened with most of the sound work. This form for sound is very primitive and cannot be used for serious work.
Figure 59.This sound function is found in the computer’s motherboard.
In other motherboards, you can find real sound controllers built-in – this is not AC’97 sound. There is, you see, one or more chips, for example, from the companies Creative or Yamaha, so it corresponds with a genuine sound card.
Figure 60. When the sound function is integrated into the motherboard, there are three sound plugs.
USB based sound
USB is a smart technology. It is a little digital plug, which is connected to the computer’s motherboard. The idea is, that you can connect almost anything with USB. The most common USB devices are, for example, digital cameras, scanners, mice and modems, but there are also sound devices. I can mention:
These devices are not enormously widespread, but they exist and they work very well. The advantage is, that USB devices are external; they don’t have to be installed in the computer. They are usually small boxes, which are connected with a standard cable, which also can be used with a portable computer. The devices can easily be connected to a computer, which already has a sound card installed. You just have to select, which device to use for playing:
Figure 61.This computer has three sound devices installed.
USB sound devices usually work both with analog signals and digital data. D/A- and A/D converters are, therefore, built-in in the small boxes. Sony supplies, for example, a USB box for their MiniDisc. This little box has an analog minijack plug in the one end and a USB plug in the other. So you can play mp3 files on the computer via the box, which sends signals to the MiniDisc’s port.
Figure 62. USB interface with an analog port for a MiniDisc.
Sound cards are unbelievably complicated to describe. There is hardware, there is software, and there are oceans of standards, interfaces and specifications. Furthermore you have to be aware of the fact that a sound card can be used for many different purposes. There are not very many, who need to use all the options of a sound card, but there can be no harm in making yourself acquainted with its different facets.
My examination is, therefore, in no way complete. But in the following chapters, we will dive headlong into this fascinating technology and I hope that you will end up understanding a bit more about the subject.