Ultrasonic
Decibel and amplitude ratio
Decibels from an amplitude ratio and back, and the gain change that moves a signal from one screen height to another.
For reference only — verify against your procedure and the governing code.
Nothing on this calculator changes with units.
dB
% FSH
% FSH
Result
- Ratio → dB
- 6.021dB
- dB → ratio
- 1.995×
- Gain change
- 6.021dB
Positive dB means add gain; negative means remove it.
Formula
- dB = 20 · log₁₀(A₁ / A₂)
- A₁ / A₂ = 10^(dB / 20)
Units. Decibels and screen-height percentages have no units to switch.
Assumptions and limits
- Amplitude (not power or intensity) ratios, and a linear display: check vertical linearity before relying on screen heights.
Sources
- ASTM E1316-09a, Standard Terminology for Nondestructive Examinations — Section I: decibel, near field, skip distance.
More ultrasonic calculators
For reference only — verify against your procedure and the governing code.
Standards and documents are cited by their publishers' names to identify them. TRACE is not affiliated with, endorsed by or sponsored by ASTM International, ASME, the U.S. Nuclear Regulatory Commission, NIST or the Laboratoire National Henri Becquerel. Formulas are paraphrased and cited by clause; get the documents themselves from their publishers.