320 The Digital Filmmaking Handbook, 4E

Audio Levels Metering

The perception of audio is very subjective, and what sounds loud to one person might not sound loud to another. The loudness of audio is measured in decibels (dB), which represent a subjective scale: an audible increase in loudness means that the volume of the audio has increased 1dB. Software and hardware manufacturers put dB increments on the audio level meters that are a part of the equipment (see Figure 15.1), but 1dB on your video deck might sound louder than 1dB in your editing application. Unfortunately, this is a good introduction to the ambiguities you’ll encounter when working with audio. Despite attempts to define it, sound is very subjective.

Digital audio meters place 0dB at the top of the scale (see Figure 15.1), and the midpoint is placed at –12, –14, or –20dB, depending on the manufacturer. Because it varies from one piece of equipment to another, this midpoint is also referred to as unity. The sounds louder and softer than unity might vary from one piece of equipment to another, but the sounds that fall exactly at unity should have the same volume on any piece of hardware or software.

Figure 15.1

Digital audio meters provide a visual display to indicate the loudness of your sound.