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.
- 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.
- 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.*
- 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