Sound

2. Recording and Replay

There are a number of devices that are involved in capturing analogue sound and converting it in to a digital file for use by a computer:

Microphone - Recording sound

A microphone is an input device for sensing incoming sound. It converts sound into an electrical signal. This signal is then passed on to the ADC (Analogue-to-Digital converter) in the sound card.

Sound card - Converting sound

A sound card has two jobs. It has to be able to convert an analogue signal into a digital one for storage. It also has to be able to convert stored digital signals into an electrical signal to send to the speakers.

The first job is performed by the Analogue-to-Digital Converter (ADC). The second is performed by the Digital-to-Analogue Converter (DAC). We will discuss how this happens in later pages.

Speakers - Replaying sound

To replay a sound, the file is opened and the binary numbers are fed through the DAC (digital-to-analogue converter). This produces an analog output that is then amplified in some way (internal or external amplifier) to produce enough power for the speakers or ear-phones in the system.