Ultrasonic
Wavelength and near-field length
Wavelength from velocity and frequency, and the near-field length of a circular or square element.
For reference only — verify against your procedure and the governing code.
ASTM E494 Table X3.1 typical values, converted from the source's m/s.
Result
- Wavelength λ
- 1.18mm
- Near-field length N
- 34.17mm
Formula
- λ = V / f
- Circular: N = D² / 4λ = D² · f / 4V
- Square (side A): N = 1.35 · A² / 4λ
Units. Computed in m/s, MHz and mm; shown in mm/µs and mm, or in./µs and in. Frequency is in MHz in both systems.
Assumptions and limits
- Unfocused, flat element at its nominal frequency. Actual beams depend on bandwidth and damping; ASTM E1065 gives these for reference.
- No formula is given here for other rectangular elements: E1065 provides only the circular and square cases.
Sources
- ASTM E587-20, Standard Practice for Ultrasonic Angle-Beam Examination by the Contact Method — §4.1–4.2 refraction; §4.3.3 wavelength = velocity / frequency.
- ASTM E1065-08, Standard Guide for Evaluating Characteristics of Ultrasonic Search Units — Annex A6, Eqs (A6.1) and (A6.2) near-far-field transition.
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.