Sound itself, as a physical element, travels in waves. The intensity of the sound is measured in amplitude, and this determines the volume of the sound. This volume is measured in decibels and commonly measures from -20 db, which is basically no sound, to +3 db, which is higher than full levels with lots of cracking and distortion. When you are editing your film you need to keep an eye on the audio volume levels to make sure the sound is as great and consistent as possible. You always want to keep the main sound, and not background noises or music, between 60% and 100% amplitude. Never let the sound go above +2 db or under -15 db. Sound is also composed on wave frequency, measured in Hertz, and Pitch, which indicates where on the musical scale a sound fits. These elements are not quite as important when recording sound from a scene, but it is still a good idea to consider that sound is measured in a multitude of ways because it has a variety of aspects to it.