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Materials Science in Additive Manufacturing TPMS for perfect sound absorption

with unusual acoustic properties, which cannot be found acoustic metamaterials. In general, lengthened paths or
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in natural materials, such as the reflection, absorption, multiple resonant cavities lead to enhanced dissipation in
filtering, guided waves, focusing, superlensing, and acoustic the structure-coiled absorbers. 15
stealth of sound waves. Acoustic metamaterials are usually Triply periodic minimal surface (TPMS) is a potential
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at the subwavelength scale, whose characteristic length is sound absorption metamaterial due to its pore size and
smaller than the wavelength of acoustic waves, which porosity that can be adjusted within the typical range of
necessitates accounting for viscous and thermal losses. 3 other open-pore porous materials. In addition, TPMS also
Sound absorption metamaterials, a subset of acoustic has lightweight and high-strength characteristics. TPMS
metamaterials, have broad application prospects in sound structures, including primitive, gyroid, and diamond, have
absorption and noise reduction in ships, submarines, been manufactured by stereolithography and tested using
airplanes, automobiles, and construction fields. Sound the two-microphone impedance method. The results
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absorption metamaterials include thin-film acoustic indicate that diamond exhibits excellent sound absorption
metamaterials, 2D plate-like acoustic metamaterials, performance among these three types of structures across
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Helmholtz-like acoustic metamaterials, and porous a wide bandwidth. The sound insulation performances of
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structural acoustic metamaterials. Thin-film sound- primitive and gyroid sandwich panels have been investigated;
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absorbing structures require large cavities and have poor the gyroid sandwich panel is significantly superior to the
mechanical properties. The perforated plate sound absorption primitive sandwich panel, and the gyroid structure can
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structure can be approximated as an array of Helmholtz achieve sound insulation of more than 20 dB across a
resonators arranged in a regular manner; however, its narrow broad frequency range. This demonstrates the advantage
sound absorption peak limits its application. Porous sound of TPMS structures in sound absorption and insulation;
absorption structures convert sound energy into thermal however, their bandwidth and low-frequency absorption
energy due to viscous loss generated by the propagation remain limited. Porosity affects sound absorption, and
of sound waves inside the pores, thereby achieving sound the reduced porosity of TPMS structures can improve the
absorption effects. However, the resonant absorption peak sound absorption coefficient. A composite structure with
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of porous structures is related to the thickness of the pores, TPMS and a MPP structure has been proposed, displaying
due to the quarter wavelength resonance of the hard-backed good sound absorption performance. The maximum sound
porous material. Due to the thickness limitation of porous absorption coefficients exceed 0.8, with the resonance
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structures, their broadband and low-frequency sound frequency shifting to lower frequencies. A modular
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absorption performance is not ideal. multicavity geometry with TPMS and aerogel-3D has been
Design methods for expanding the sound absorption designed, offering application-specific low-frequency and
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bandwidth of metamaterials have garnered significant broadband absorption performance. The ultrabroad half-
attention from researchers. Based on the performance absorption band from 0.96 to 6.00 kHz is obtained by the
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of the absorber array, which features varying sizes and multicavity and multilayered design.
spatial arrangements of the component absorbers, it is In addition to the multicavity composite design, the
proposed to arrange three subcavities of different depths graded structure design can broaden the absorption
in parallel on a microperforated plate. This design frequencies of porous structures. The average sound
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effectively expands the sound absorption bandwidth of absorption coefficient of four-layer gradient compressed
the microperforated panel absorber by utilizing the local porous metals with different permutations is 60.33% at
resonance effect of subcavities of different depths and 100 – 6000 Hz, with a total thickness of 11 mm. The
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frequencies. A series-parallel-coupled composite micro- gradient interface between the porous media inside the
perforated panel (MPP) sound-absorbing device was sound absorption structure is beneficial for improving
proposed, and a theoretical model was established based the sound absorption performance, as sound waves are
on the acoustic-electric analogy method, experimental absorbed by secondary reflection due to impedance
verification was conducted, and the results indicated that mismatch when encountering the interface inside the
the series-parallel-coupled sound-absorbing device could porous structure. A 2D continuously graded phononic
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broaden the absorption bandwidth. According to the crystal (CGPC) has been proposed, capable of enhancing
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characteristic that the resonant frequency of MPP shifts acoustic scattering and lengthening propagation paths,
with changes in cavity depth, MPPs with different cavity leading to increased energy dissipation and improved sound
depths have been designed and optimized. Different absorption performance. Compared to the uniform porous
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depths of honeycomb cores can achieve broadband sound structure, the first resonance frequency of CGPC shifts to
absorption. It is demonstrated that the multiple internal a lower frequency, and the increase in sound absorption
reflections could be harnessed to achieve highly absorptive is associated with the increased absorbed energy. The
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Volume 4 Issue 1 (2025) 2 doi: 10.36922/msam.5737