Noise reduction technology for broadband frequency attenuation include the design of special solutions for a/c engine born noise with application in hot as well as cold sections.
High - temperature segmented liners
Novel design concepts include segmented and macro-perforated liners for applications up to 650oC. Novel materials have been utilised like Ceramic Hollow Spheres (from ATECA)
with different attenuation characteristics are attached together to
form a single liner. This approach enables targeting of specific noise
sources with one absorbing element.
Ceramic Hollow Spheres arrangements (ATECA)
Continuous research efforts have led to Bi-directional segmented macro-perforated hot stream liners
that are machinable and easily integrated with the bearing structure.
Coupon - level testing for different Mach numbers and working
temperatures has proven the liner efficiency in terms of noise reduction. Also, severe and vibratory testing, according to engine manufacturers' standards, has proven their structural integrity and acoustic immunity to such conditions.
Micro- and macro-scopic view of Bi-directional segmented macro-perforated hot stream liners
You may also see current research activities in the development of acoustic liners here: R&D > a/c noise attenuation