# Advanced Sound Insulating Materials: An Analysis of Material Types and Properties
## 3 Results
\begin{table}
\begin{tabular}{p{113.8 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Name** & **2015–2019** & **2020–2024** & **All Years** & **Share [\%]** & **Chi-Square** \\ \hline Total & 12 & 64 & 76 & 100.0 & \(\chi^{2}\) \\ \hline Document type & & & & & \\ \hline Conference paper & 3 & 7 & 10 & 13.16 & \(\chi^{2}=2.04\) \\ Journal article & 9 & 55 & 64 & 84.21 & (df = 2, \(p=0.36\)) \\ Other & 0 & 2 & 2 & 2.63 & (df = 2, \(p=0.36\)) \\ \hline Material type & & & & & \\ \hline Composites & 3 & 25 & 28 & 36.84 & \\ Fibrous & 6 & 35 & 41 & 53.95 & \(\chi^{2}=1.77\) \\ Polymers & 1 & 5 & 6 & 7.89 & (df = 4, \(p=0.78\)) \\ Porous & 5 & 17 & 22 & 28.95 & (df = 4, \(p=0.78\)) \\ Nanomaterials & 1 & 10 & 11 & 14.47 & \\ \hline Material properties & & & & & \\ \hline Chemical & 3 & 7 & 10 & 13.16 & \(\chi^{2}=1.68\) \\ Mechanical & 4 & 23 & 27 & 35.53 & \(\chi^{2}=1.68\) \\ Physical & 5 & 30 & 35 & 46.05 & (df = 3, \(p=0.64\)) \\ Thermal & 4 & 25 & 29 & 38.16 & \\ \hline Research methodology & & & & & \\ \hline Experiment & 12 & 59 & 71 & 93.42 & \(\chi^{2}=0.31\) \\ Literature analysis & 3 & 20 & 23 & 30.26 & (df = 2, \(p=0.86\)) \\ Conceptual & 4 & 17 & 21 & 27.63 & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Publications by year in all categories. shells as agricultural waste [42], waste wool fibers [43], and eco-friendly natural fiber composites [11]. In addition, researchers have analyzed the effect of chemical treatments, such as sodium hydroxide and potassium permanganate, on bamboo fibers [15]; the use of polymer biocomposites reinforced with common banana fibers [12]; the effect of sample thickness and fiber/epoxy resin ratio on the acoustic properties of jute and loofah fiber-reinforced biocomposites [18]; the use of microperforated panels in combination with a porous layer [44]; the properties of a liquid metal (LM) that has been uniformly dispersed in carboxymethyl cellulose (CCNF) nanofibers to produce a balanced CCNF/LM aerogel by lyophilization [45]; the sound absorption properties of biduri fiber [46] and epoxy resin reinforced jute and coir fiber composites [5]; the use of flax composites with epoxy resin [47]; the effects of non-woven fabric made from 100% kapok [48]; and the properties of epoxy composite with cylindrical loofa fibers [49]. The results of research works include the development of a multilayer microperforated polyvinyl butyl nanofiber membrane [50], a fuzzy logic-based model [1], a new nanofiber membrane [51], a new method for the creation of triple-array nanofibrous aerogels [52], cellulose-based fibers from the stem of the plant _Alcea rosea_ L. (ARL) [53], an innovative microwave-absorbing aramid honeycomb (MAAH) [54], and a design strategy for nanofibrous aerogels [55]. The third type of sound-insulating materials is porous materials. Studies have shown that aerogels reduce thermal conductivity and increase sound absorption [56], effectively absorb sound in the frequency range of 2000-6300 Hz [57], exhibit moisture resistance, and have the ability to recover their shape after large deformations [55]. Researchers also revealed that carboxymethyl cellulose aerogels (CCSA), prepared by targeted freezing, have excellent acoustic, thermal, and mechanical properties [58], as do polyimide-polyvinylpyrrolidone (PI-PVP) aerogels with a hierarchical cell structure [59]. The importance of modifying graphene oxide-polyvinyl alcohol aerogels with a plasticizer (glycerol) and a cross-linking agent (glutaraldehyde) is also highlighted, leading to materials with high flexibility, low thermal conductivity, and good sound absorption [60]. In addition, research has focused on improving sound absorption in epoxy fiberglass fabric composites [61], composite aluminum foams [46], and composites made from cotton waste and pea stalks [10]; developing methods of producing lightweight cement composites [62], porous rubber foam composite sound absorbing materials [63], and composite double-chamber sound absorbing structures [64].