Practical Recording Techniques, 7th Edition

Appendix A dB or Not dB

In the studio, you need to know how to set and measure signal levels and match equipment levels. To learn these skills, you must understand the decibel.

Audio level is measured in decibels (dB). One dB is the smallest change in level that most people can hear—the just-noticeable difference. Actually, the just-noticeable difference varies from 0.1 dB to about 5 dB, depending on bandwidth, frequency, program material, and the individual. But 1 dB is generally accepted as the smallest change in level that most people can detect. A 6- to 10-dB increase in level is considered by most listeners to be “twice as loud.” Sound pressure level, signal level, and change in signal level all are measured in dB relative to some reference ...