The decibel is a relative amplitude ratio: every 6 dB doubles (or halves) the amplitude

The decibel (dB) is a logarithmic relative unit, not an absolute one. In digital audio, 0 dB SPL conventionally represents the maximum reproducible amplitude; negative values indicate levels below that maximum. The key rule: every 6 dB step halves or doubles the linear amplitude. Every 20 dB step multiplies or divides by 10. This logarithmic scale reflects how the ear perceives loudness. Because dB measures a ratio, there is no fixed 0 dB; its definition depends on the reference (digital maximum, acoustic threshold, etc.). Analog acousticians often set 0 dB at the threshold of hearing rather than the maximum.

Examples

Amplitude 1.0 → 0 dBFS; amplitude 0.5 → −6 dBFS; amplitude 0.25 → −12 dBFS; amplitude 0.001 → −60 dBFS.

Assessment

If a signal is at −18 dBFS, how many times must its linear amplitude increase to reach −6 dBFS? Express the answer as a multiplication factor.