Tomography Systems and Sound Manipulation Using Acoustic

Siti Zaleha Abdul Hamid*, Siti Nur Nasha Azlika Hamidon, Herlina Abdul Rahim, Ruzairi Abdul Rahim

Abstract

Conventional materials in noise reduction such as concretes, woods, foams and glasses is
widely used in building to reduce noise in our surroundings. However, these materials exhibit
very low capability in reducing low frequency noise. Metamaterials are introduced to provide
better sound reduction in low frequency replacing the conventional bulky materials with less
weight and cost. Hence, this study performed to investigate the feasibility of acoustic
metamaterials in sound reduction. Five samples of acoustic enclosures are fabricated using
different materials with dimension of 100 mm3. Wood acoustic enclosure are fabricated
manually while acrylonitrile butadiene styrene (ABS), poly lactic acid (PLA), PLA with
metamaterial (1 mm thickness of cavity w ) and PLA with metamaterial (5 mm thickness of
cavity w ) acoustic enclosures are fabricated digitally using three-dimensional (3D) printing
method. Performance analysis for acoustic enclosure samples was measure based on decibel
drop, d to show the difference in sound pressure level before and after acoustic enclosure is
placed on the sound source. PLA acoustic enclosure with metamaterial of 5 mm thickness is
able to reduce sound level better than the rest of acoustic enclosures samples with the highest
reduction of sound pressure level, 26.1 dB occurred on 800 Hz and proved that a greater
thickness of metamaterial exhibit better sound reduction.