£1,156.44 plus VAT

SKU: HAMA Category:

In stock


NPL High Quality Acoustic Absorber for Ultrasonic Applications

This unique high quality absorber material, available only from Precision Acoustics, has special acoustic properties which make it ideal for a range of applications, including:

  • Absorbing targets for radiation force balances, to minimise the errors associated with the reflecting targets of most commercially available radiation force balances.
  • Low ultrasonic echo (anechoic) material as a specialist coating for hydrophone mounts used for characterisation of medical ultrasonic equipment employing continuous-wave or long toneburst excitation.

Physical Specification

  • Based on polyurethane rubber material Two layers: top layer – acoustic impedance matched to water backing layer – partially air-loaded to increase transmission loss.
  • Interface between the two types of material pyramidal in structure to scatter incident ultrasound.
  • Dimensions: 200mm x 250mm x14mm.
  • Coefficient of linear thermal expansion is 200ppm/oC.
  • Density of 1010 + 20kg / m3.
  • Specific gravity is 1.01.
  • The Longitudinal wave speed (1-10MHz) ≈1500m/s.
  • Acoustic Impedance is 1.5 MRayls.
  • There is residence to Isopropyl Alcohol (IPA) and Tricholethylene.
  • It can be affected by Ketones (MEK, Acetone) – Swell.
  • Dichloromethane – Swell and breakdown.
  • Avoid prolonged exposure to Ozone and UV.
  • The stability is very stable due to cross-linked nature of polymer.
  • Material can be precision cut in various geometries to meet exact end-user requirements, e.g., simple discs of 50mm diameter.

Acoustical Specification

  • High transmission loss, > 30dB/cm/MHz.
  • High echo-reduction, > 42dB at 1MHz degrading to 35dB at 10MHz.
  • The NPL absorber fully meets the requirements for radiation force balance targets, covering the frequency range 1-15MHz3.
  • HAM A absorber has been used to perform power measurements up to 20 watts.*


  1. Robert T. Hekkenberg, Klaus Beissner and Bajram Zeqiri, Therapy-level ultrasonic power measurement, Final Technical Report for Project SMT4-CT96-2139, 2000
  2. Bajram Zeqiri and Catherine J. Bickley, A new anechoic material for medical ultrasonic applications, Ultrasound in Med. & Biol., Vol. 26, No. 3, pp. 481-485, 2000
  3. IEC 61161 (1992). Ultrasonic power measurements in liquids in the frequency range 0.5 to 25MHz. IEC, Geneva, Switzerland