Sound is one's artistic medium and sound engineers create sonic artwork from it. This chapter talks about sound and explores how to use the equipment. The speed of sound is commonly quoted as being around 344 meters per second- for dry air, at 20°C, at sea level. Meters, faders, and the scales on many equipment knobs are in decibels (dBs), so it is vitally important to understand the concept in order to use audio equipment correctly. When using a VU meter it is important to leave enough headroom for instantaneous peak levels without lighting the peak LED. Measured in dB, audio dynamic range is the difference between the lowest and highest signal levels an audio device (or system) can record, store, or reproduce. Larger (or wider) dynamic ranges are better. The eardrum’s motion is an analog of the sound wave’s air pressure differences, which are an analog of the motion of the original vibrating or oscillating sound source.