## 4 Conclusions  
We developed a non-woven fabric mixed with aerogel ellipsoidal particles that significantly enhances acoustic properties. The thermal conductivity of this material was equivalent to still air (0.026 W/(m\(\cdot\)K)), and the average sound absorption coefficient of this material at 500-1600 Hz at a thickness of 10 mm was more than twice that of Thinsulate, a common sound-absorbing material for automobiles. When applied throughout a vehicle's interior, this material is expected to reduce noise by approximately 40% and improve fuel efficiency by around 4% due to a roughly 30% reduction in energy consumption for air conditioning, although the total weight of the sound-absorbing and heat-insulating materials may increase.  
Previously reported porous materials with fine porous and soft sites exhibited excellent heat insulation and sound absorption properties but were brittle and prone to damage. Consequently, their use in automobiles was restricted to locations not exposed to physical stresses. The new aerogel particle-mixed non-woven fabric integrates nanoporous ellipsoidal particles, with long sides ranging from tens to hundreds of microns, into non-woven fabrics with voids of similar dimensions. This composition enhances its resistance to shock and vibration. Additionally, the application of a skin material reduces particle shedding, allowing its use in parts exposed to harsh conditions including external areas and drive units.  
Conceptualization, D.K.; methodology, D.K.; computational analysis, D.K., H.O. and T.Y.; experimental validation, D.K. and M.K.; data curation, D.K.; writing and editing, D.K.; supervision, J.O. All authors have read and agreed to the published version of the manuscript.  
Figure 11: Measured thermal conductivity of particle-mixed non-woven fabric + skin material.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & **500–1600 Hz** & **W/Skin Material** & & \\
**Bulk Density of** & **Thickness** & **Average** & **500–1600 Hz** & **Airflow** \\
**Non-Woven Fabric** & **(mm)** & **Sound** & **Average** & **Resistance** \\
**(kg/m3)** & **(mm)** & **Absorption** & **Sound** & **@0.5 mm/s** \\  & & **Coefficient** & **Absorption** & **(Pa-s/m)** \\ \hline PET non-woven fabric 1 & 16.2 & 10.1 & 0.14 & 0.38 & 102 \\ \hline PET non-woven fabric 2 & 100.5 & 10.3 & 0.27 & 0.39 & 1500 \\ \hline Particle-mixed & & & & & \\ non-woven fabric & 87.2 & 10.0 & 0.33 & 0.43 & 1200 \\ \hline Thinsulate & 16.5 & 10.0 & 0.15 & - & - \\ \hline \hline \end{tabular}
\end{table}
Table 3: Properties of particle-mixed non-woven fabric.  
Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Due to the nature of this research, participants of this study did not agree that their data should be shared publicly. The data presented in this study are available on request from the corresponding author. Conflicts of Interest: [PERSON], [PERSON], and [PERSON] were employed by Mazda Motor Corporation. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest.