To know an audio adapter, you should recognize nature of sound. Each sound is created by vibrations that compress air or other substances. These sound waves travel in all directions, increasing from source of the sound. When these waves reach your ear, they cause vibrations that you recognize as sound. The basic two properties of any sound are its pitch and intensity.

The time at which vibrations are created is known as pitch. It is measured in hertz (Hz), or cycles per second. One cycle is a full vibration back and onward. The number of Hz is frequency of tone; as you higher the frequency the pitch is higher.

Peoples can't hear all possible frequencies. Few people can hear sounds with frequencies less than 16Hz or greater than about 20 KHz. Actually, lowest note on a piano has a frequency of 27Hz, and maximum note has higher than 4KHz. Frequency-modulation (FM) radio stations can transmit notes with frequencies as 15KHz.

The remarkable compression ratios feasible with MP3 files, compared to normal CD-quality WAV files, is payable in part to discarding of sound frequencies that are higher or lower than regular hearing range through ripping process.

The intensity of a sound is known as its amplitude. This intensity decides sound's volume and based on strength of vibrations creating sound. A piano string e.g. vibrates softly when key is struck gently. The string swings back and forth in a narrow arc, and tone it sends out is soft. If key is struck more powerfully, though, string swings back and forth in a wider arc, creating greater amplitude and a greater volume. The intensity of sounds is measured in decibels (db). The crunch of leaves is rated at 20db, average street noise at 70db, and thunder close to at 120db.