What is sampling rate in sound?

The sampling rate is the number of samples taken from a continuous signal over a period of time (typically measured per second - Sa/s or Samples per Second).

The Nyquist - Shannon Sample Theorem states that a sample rate should be double the highest recorded frequency. Since the range of human hearing is 20Hz - 20,000 Hz, the minimum sample rate should be 40,000 Hz. CD format sample rates are 44.1kHz for this reason as well as other technical reasons.