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Acoustic absorber materials

For high levels of echo reduction and insertion loss

Unique, high performance materials

NPL has expertise in the design and development of bespoke acoustic absorber materials for immersion applications. These combine high levels of echo reduction and insertion (transmission loss) and can typically be used to line the walls of water-filled test tanks to reduce the impact of reflections on measurement and to support precision instrumentation such as radiation force balance targets.

Acoustic absorbers developed by NPL are available to order from Precision Acoustics who is the sole supplier of this product range, with the exception of HAM A-LF which is only available through NPL. The materials are summarised in the table below with web-links providing details of the material characteristics, including acoustic properties determined at NPL. The acoustic absorbers are divided in high frequency (above 100 kHz) and low frequencies down to 10 kHz.

High frequency anechoic materials for medical applications (above 100 kHz)   

Name           Description

Acoustic absorber material for application as a radiation force balance target (RFB). Characterised using the NPL facilities, the material meets the stringent specification in terms of echo reduction and transmission loss demanded by the relevant IEC specification standard  down to a frequency of 120 kHz.
The absorber can be easily retrofitted to RFB’s which currently employ the successful NPL-developed HAM A acoustic absorber extending the operational frequency downwards. Details of the new absorber, designated HAM-LF, have been ​​published.

*Only available through NPL


High quality material for medical ultrasound applications such as radiation force balance targets. Find out more

Aptflex F28

Provides a cost-effective method of absorbing ultrasonic reflections ensuring acoustic isolation. Find out more

Aptflex F28P

Pyramidal structured absorber for radiation force balance targets designed for acoustic powers greater than 20W, but less than 100 W. Find out more

Aptflex F36

Two-part mix kit version of the Aptflex F28. It has the same acoustic properties of the tile Aptflex F28 but can be cast into specific shapes.
Find out more

Low frequency anechoic materials for underwater acoustics applications (down to 10 kHz)

   Name             Description
Aptflex F48

Designed to meet the requirements to reduce reflections in sub MHz frequency acoustic test tanks. Find out more

Apltile SF5048

Single-ply absorber made from Aptflex F48 with a structured front surface designed to scatter incident sound. Find out more

Alberich tile

Structured material based on Aptflex F48, designed to boost insertion loss at low acoustic frequencies. Find out more

The products which have been developed and tested by NPL and Precision Acoustics have the NPL Technology Applied status, this is a co-branding scheme for instrumentation and software technology developed by NPL and incorporated into a range of commercial products.

acoustic absorbers

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