Simplify the following text for a Grade 6 native English-speaking person.
Original: A sound card ( also known as an audio card ) is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs .
Simplified: A sound card ( audio card ) is the part of the Computer hardware that controls the input and output of the sound signals . A sound card is what is known as an expansion card .