## 2 Materials and Methods
### Experimental Framework for Acoustic Properties Assessment
The measurement process includes both a 100 mm diameter and a 29 mm diameter impedance tube to collect data across the full standard acoustic frequency range (125 Hz to 4000 Hz). Low-frequency absorption data (125-1000 Hz) were collected using the 100 mm tube, whereas high-frequency data (2000-4000 Hz) were collected from the 29 mm tube measurement. This results in a total of 27 samples per tube size and 54 samples overall. Each sample is composed of 10 layers in total, with the bottom two layers uniformly printed in all of the samples using a parallel toolpath design pattern and 100% infill density. These base layers are implemented to prevent the formation of open vertical channels, which could potentially invalidate the impedance tube tests. Figure 7 illustrates the configuration of each sample, with each color representing a specific infill pattern applied to the layers. After robotic EAM of the cylindrical samples, they were kept in an environmentally controlled room at 65% humidity and 24 \({}^{\circ}\)C at Mushroom Research Center (MRC, State College, PA, USA) for 7 days. The samples were air-dried for 24 h and then oven-dried at 90 \({}^{\circ}\)C for 48 h. Due to deformation and warping during growth and drying, as well as the precision required for impedance tube tests, additional post-processing was necessary. The samples were carefully sanded using a belt sander to achieve precise roundness for an exact fit within the impedance tubes for accurate acoustic measurements. An impedance tube was used to measure the normal incidence sound absorption coefficients at both high  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Factor** & **F1:** & **F2:** & **F3:** & & **F4:** \\
**Experiment** & **Infill \%** & **Infill \%** & **Infill \%** & **Infill Pattern** & & **Layer Ratio** \\
**No. ** & **(Non-Planar)** & **(Planar)** & **(Planar)** & **(Planar)** & **(Non-Planar-Planar)** \\ \hline S1 & L1 & 90\% & L1 & 90\% & L1 & DGC & L1 & 1.7 \\ S2 & L1 & 90\% & L2 & 75\% & L2 & Parallel & L2 & 2.6 \\ S3 & L1 & 90\% & L3 & 60\% & L3 & 3D & L3 & 3.5 \\ S4 & L2 & 75\% & L1 & 90\% & L2 & Parallel & L3 & 3.5 \\ S5 & L2 & 75\% & L2 & 75\% & L3 & 3D & L1 & 1.7 \\ S6 & L2 & 75\% & L3 & 60\% &and low frequencies for each sample group, with three measurements taken per sample. This method provided a quantitative analysis of how different toolpath planning factors--namely infill percentage of planar and non-planar layers, infill patterns of the planar layers, and ratios of non-planar to planar layers--affect acoustic absorption coefficient across a range of frequencies. In the impedance tube test, a sound source sends broadband sound waves toward a sample, generating a pattern of forward and backward traveling waves inside the tube. Calculations of normal incidence absorption coefficients are then performed following standard ASTM E1050-19 to compare sound absorption in the 500 Hz to 6.4 kHz frequency range [32]. Statistical analysis was performed using Minitab (Web-Based Version. Minitab LLC: State College, PA, USA. [[https://app.minitab.com/](https://app.minitab.com/)]([https://app.minitab.com/](https://app.minitab.com/)) (accessed on 6 May 2025)) to study the impact of different levels of factors on mean performance (absorption coefficients) and variability in performance (signal-to-noise ratios, SN).