The sound is the pressure disturbance created over air particles above and below atmospheric pressure. It is a mechanical wave which requires a medium to propagate. The sound can generate from a source, then travels through a medium and finally is received by the receiver. The noise is an unpleasant or unwanted sound that is undesired by the receiver. This unwanted sound is absorbed by the sound absorbing (SA) materials. This paper presents a complete comprehensive literature survey for the SA materials and organized the information in the following manner. First, the phenomenon behind SA mechanism is being explained, then the detailed information of existing SA materials with their classification is reported. After that, the factors associated with the sound absorption that influences the sound absorption coefficient (SAC) is being presented. Finally, the theoretical models for porous materials are being discussed followed by the details of price comparison of natural and synthetic fiber-based sound absorbers and the applications of SA materials of various acoustical products. There are a lot of researches going on to develop new acoustic materials and hence this paper will help the researchers to know about the existing SA materials and also help them to develop new acoustic materials by considering significant information related to sound absorption.

中文翻译：

---

多孔吸声材料的分类，吸声相关因素及理论模型综述

声音是在高于和低于大气压的空气颗粒上产生的压力扰动。这是机械波，需要介质传播。声音可以从声源产生，然后通过介质传播，最后被接收器接收。噪声是接收机不希望的令人不快或不想要的声音。有害的声音被吸声（SA）材料吸收。本文提供了有关SA材料的完整的综合文献调查，并按以下方式组织了信息。首先，解释了SA机制的现象，然后报告了现有SA材料的详细信息及其分类。之后，提出了与吸声相关的影响吸声系数（SAC）的因素。最后，讨论了多孔材料的理论模型，然后详细介绍了天然和合成纤维基吸声材料的价格比较以及各种声学产品中SA材料的应用。开发新的声学材料的研究很多，因此本文将帮助研究人员了解现有的SA材料，并通过考虑与吸声有关的重要信息来帮助他们开发新的声学材料。