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Precision Acoustics


£1,361.00 excl. VAT

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

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SKU HAMA Category

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NPL high quality acoustic absorber for ultrasonic applications

This unique high quality absorbernpl technology applied 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: 200 mm x 250 mm x 14 mm
  • Coefficient of linear thermal expansion is 200 ppm/oC
  • Density of 1010 + 20 kg / m3
  • Specific gravity is 1.01
  • The longitudinal wave speed (1 MHz to 10 MHz) ≈1500 m/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 50 mm diameter

Acoustical Specification

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


  • Robert T. Hekkenberg, Klaus Beissner and Bajram Zeqiri, Therapy-level ultrasonic power measurement, Final Technical Report for Project SMT4-CT96-2139, 2000
  • 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
  • IEC 61161 (1992). Ultrasonic power measurements in liquids in the frequency range 0.5 to 25MHz. IEC, Geneva, Switzerland