The following table can be used as a quick reference for the wavelength, speed of sound of most commonly used material. Some useful definition includes:

  • Near Surface Resolution: Minimum distance from the scanning surface where a reflector (SDH, FBH) can be detected with an acceptable SNR.
  • Far Surface Resolution: Minimum distance from the inner surface where a reflector (SDH, FBH) can be detected with an acceptable SNR.
  • Lateral Resolution – Minimum distance between two adjacent defects located at the same depth are clearly detected
  • Axial Resolution – Minimum distance along the acoustic axis for which two adjacent defects are clearly detected

Velocity (m/sec) Wavelength (Long) – mm Attenuation (Neper/mm)
1 Ne= 8,686 dB
Aluminum 6374 3111 2,8 1,3 0,6 0,4 (10 Mhz)
Bone -Human Tibia 4000 1970 1.8 0.8 1.4 460 (2,9 MHz)
Concrete 3900 – 4700 1.8 0.8 1.4 7-13 (0,2 MHz)
Composite – Carbon-epoxy 2950 1.3 0.6 0.3
Copper 4759 2365 2.1 1.0 0.5
Glass 5660 3420 2.5 1.1 0.6 2 (10 Mhz)
Cast iron 5957 3224 2.6 1.2 0.6
Magnesium 5823 3163 2.6 1.2 0.6
Polyethene 2100-2400 850-920 1.0 0.4 0.2 100-300 (5Mhz)
Natural Rubber 1600 0.7 0.3 0.2 36,6 (0,35)
Mild Steel 5960 3239 2.6 1.2 0.6
Tool Steel 5874 3179 2.6 1.2 0.6 4,94 (MHz)
Stainless Steel 5980 3297 2.7 1.2 0.6
Titanium 5130 3182 2.3 1.0 0.5
Water 0 ƒ 1402 0.6 0.3 0.1
Water 20 ƒ 1482 0.7 0.3 0.1
Water 30 ƒ 1509 0.7 0.3 0.2
Air 278 0.1 0.1 0.03