Page 35 - MSAM-4-1

Materials Science in Additive Manufacturing TPMS for perfect sound absorption

30 mm (Figure 7). There are four main resonance 3.2. Sound absorption characteristics of gyroid and
absorption peaks above 1500 Hz, namely 2670, 3310, multicavity-gyroid structures
4560, and 6200 Hz. The ratio of the first absorption The sound absorption coefficient curves of gyroid
peak wavelength to structure thickness (λ peak /T) is 4.34. structures with individual cavity and multicavity-gyroid
This represents a subwavelength absorption peak, as structures are displayed in Figure 8. The first resonance
the λpeak/T is >4, which exhibits a quarter wavelength peak of the gyroid structure was identified. The analysis
resonance frequency (QWRF) of 2891 Hz at 30 mm. The of resonance peaks is listed in Table 6. As the thickness
sound absorption coefficient of the first, second, third, of the gyroid structure increases from 12 to 30 mm, the
and fourth absorption peaks are 0.944, 0.944, 0.499, and resonance peaks decrease from 5590 to 2000 Hz, indicating
0.240, respectively. These four peaks correspond to the that the resonance absorption peak of the gyroid structure
acoustic resonance of four cavities with different depths. shifts toward lower frequencies as the thickness increases.
The resonance peak of the multicavity structure without A quarter-wavelength resonance has been found in
porous structure filling is narrow, and the frequency periodic porous structures with hard-backing, and the
8
band of the first peak with sound absorption coefficients QWRF is equal to c/4T, where c is the wave propagation
exceeding 0.5 is only 210 Hz. speed in air and T is the thickness of porous structures.
The theoretical QWRF of periodic porous structures with
6, 12, 18, 24, and 30 mm is 14458, 7229, 4819, 3614, and
2891 Hz, respectively (i.e., f = c/4T; c = 347 m/s). The λ peak /T
of the gyroid structure is calculated and listed in Table 6.
The uniform gyroid structures present a subwavelength
absorption peak, as the λ peak /T is >4. The experimental first
absorption peak frequency of the Gyroid-24 mm structure
is 2590 Hz, which is 1024 Hz lower than the QWRF,
suggesting that the sheet-based gyroid structure has better
absorption capability than the theoretical periodic porous
structures.
Five peaks are visible on the spectrum of the multicavity-
gyroid structure, the first four peaks (2160, 2670, 3600, and
4810 Hz) corresponding to the four individual absorption
peaks for each cavity with Gyroid-12 mm, Gyroid-18 mm,
Figure 6. A two-microphone impedance tube Gyroid-24 mm, and Gyroid-30 mm, respectively. The fifth

A B

Figure 7. Sound absorption coefficient curves of multicavity structures. (A) Multicavity model without TPMS. (B) Sound absorption curve of multicavity
model
Abbreviation: h: Height of cavity

Volume 4 Issue 1 (2025) 8 doi: 10.36922/msam.5737