Sound is vibrations that travel through the air as sound waves, which are measured in decibels. The amplitude of the wave determines the loudness of the sound. Acoustics help absorb or reflect sound waves. Soft materials like carpet are good for absorbing sound and preventing echoes, while hard materials allow sound waves to bounce off walls and cause reverb. Interior locations are better for recording sound due to control over acoustics, unlike exterior areas with unpredictable noise levels. However, sound panels are sometimes not used for live performances so sound can reach all audience members.