Page 38 - MSAM-4-1

Materials Science in Additive Manufacturing TPMS for perfect sound absorption

Table 8. Sound absorption characteristics of uniform
I‑Wrapped Package (IWP) and multicavity‑IWP structures
Specimen Thickness, Frequency Absorption λ peak /T
T (mm) at first peak, at first
f 1 (Hz) peak, α 1
IWP-6 mm 6 - - -
IWP-12 mm 12 5480 0.574 5.28
IWP-18 mm 18 3860 0.619 5.00
IWP-24 mm 24 2670 0.750 5.42
IWP-30 mm 30 1890 0.821 6.13
Multicavity-IWP 30 2150 0.944 5.39

peak is not related to the type of TPMS structure, and the
bandgap variation depends on the thickness of the TPMS
Figure 10. Sound absorption curves of primitive and multicavity- structures.
primitive structures
3.4. Sound absorption characteristics of IWP and
Five peaks are also visible on the spectrum of the multicavity-IWP structures
multicavity-primitive structure. The first four peaks at The sound absorption coefficient curves of IWP and
frequencies of 2090, 2570, 3330, and 4590 Hz correspond multicavity-IWP are displayed in Figure 12, and the
to the four individual absorption peaks for each cavity with resonance peak analysis is listed in Table 8. The resonance
Primitive-12 mm, Primitive-18 mm, Primitive-24 mm, peaks of IWP-12 mm, IWP-18 mm, IWP-24 mm, and IWP-
and-30 mm; the fifth peak (5870 Hz) corresponds to the 30 mm are 5480, 3860, 2670, and 1890 Hz, respectively. The
second individual absorption peak of Primitive-30 mm. α of IWP-12 mm, IWP-18 mm, IWP-24 mm, and IWP-
1
In addition, the primitive structure with a single cavity 30 mm are 0.574, 0.619, 0.750, and 0.821, respectively.
primarily exhibits semi-absorption at its first peak. The five These results indicate that the resonance peak frequency
resonance peaks of the multicavity-primitive structure are of the IWP structure shifts toward lower frequencies as
all above 0.75, and the second peak achieves 100% sound the thickness increases; the sound absorption coefficient
absorption. It is demonstrated that the multicavity design of the resonance peak of the IWP structure is enhanced as
for the primitive structure can result in more absorption the thickness increases. The sound absorption coefficient
peaks and enhance sound absorption. However, the sound of the IWP structure at the first resonance peak is higher
absorption coefficient at the third and fourth peaks of the than that of the gyroid and primitive structures with the
multicavity-primitive structure is lower than that of the same thickness. The QWRF of the IWP structures with
multicavity-gyroid structure. different thicknesses are all higher than the theoretical
QWRF.
The acoustic bandgap of the primitive structure was
analyzed through the Bloch wave vector and frequency Five peaks are visible on the spectrum of the
spectrum (Figure 11). The primitive structure with a multicavity-IWP structure; the first four peaks (2150,
thickness of 18 mm exhibits a wide flat band, which is a 2660, 3450, and 4850 Hz) correspond to the four
Bragg bandgap between 3330 and 4330 Hz (Figure 11C) individual absorption peaks for each cavity with IWP-
and corresponds to the first resonance peak (f = 4150 Hz; 12 mm, IWP-18 mm, IWP-24 mm, and IWP-30 mm; the
1
α = 0.505) of Primitive-18 mm. The acoustic bandgap fifth peak (5900 Hz) corresponds to the second individual
1
of Primitive-24 mm is between 2620 and 3240 Hz, absorption peak (6130 Hz) of IWP-30 mm. The resonance
corresponding to the first resonance peak (f = 2840 Hz; of multicavity-IWP structure frequencies shifts due to inter-
1
α = 0.524) of Primitive-24 mm. There is a sharp peak resonator interactions, and the frequencies of peaks of the
1
characteristic in Primitive-12 mm, Primitive-18 mm, multicavity-IWP shift to the lower frequencies, except for
Primitive-24 mm, and Primitive-30 mm, and the the first peak. This indicates that the five resonance peaks
frequency corresponding to the attenuation sharp peak is of the multicavity-IWP are above 0.94, and the third peak
4340, 4860, 4370, and 4350 Hz, respectively; the frequency achieves 100% sound absorption.
of these attenuation sharp peaks is consistent with the The acoustic bandgap of the IWP structure was
gyroid structures. It is illustrated that the sharp attenuation analyzed through the Bloch wave vector and frequency

Volume 4 Issue 1 (2025) 11 doi: 10.36922/msam.5737