NIKOLAS: TECHNICAL SERVICES

Hi. I'm Nikolas, and I work in Technical Services at Talking Technologies. This is not a complete explanation of analogue to digital conversion, but it does tell you enough so that you can understand what it is and why USB headset adapters work.

Your mouth is an analogue device and your computer is a digital device, so it's important to understand what happens during the conversion process:

An analogue signal varies continuously, like a wave on water. When your computer converts the analogue signal to a digital signal, it re-creates the wave as a sequence of pulses.

As a simple illustration, if you get all your pencils and stand them vertically next to each other in a line, the tips will approximate to a wave. The thinner the pencils, and the more carefully you adjust their heights, make the wave less like a sequence of steps and more like a continuous wave.
A digital signal composed of 16 pulses will be a poor copy of the analogue wave. But one composed of 16 000 pulses will be much much better.

Microphone capsules are analogue devices and convert analogue voice input to an analogue voltage output. Sound systems use an analogue to digital converter chip, an ADC, to convert the analogue voltage output to a digital form that the computer can work with.

Every time an electro-magnetic field changes, it affects the current in any nearby circuit. If an interfering field affects our audio circuit, we hear it as noise. For example, we hear a background hiss, or a low hum, or the radio clicks when the washing machine starts. Noise can be continuous, intermittent, or sudden.

Although there are techniques for screening, suppressing, or filtering noise, many computers, particularly notebook computers, have a lot of electrical activity in a confined space. Economies in manufacture often mean that the microphone input circuit has little or no protection against this built-in noise. So, when your voice input reaches the processor it may have unwanted noise mixed with it.

We can tolerate quiet noise during a conversation, and enjoy loud noise during a football match. But, at a concert, any noise is unwanted.

Any computer system that has voice input, such as speech recognition or recording, is going to be more successful if we can reduce the noise content.

Unfortunately, some computer sound systems suffer from intermittent or continual electronic noise generated by power supplies, internal wiring, disk drives, and circuit boards. Many are budget devices with inadequate screening and poor noise suppression.

Microphones can't reduce, cancel, or reject, electronic noise inside the computer. The USB Headset Adapter bypasses the computer's sound system, and transfers audio directly, via the USB interface, to and from the processor as a digital data stream. So, if working with a clean signal is important, a USB adapter is an ideal solution.