EFFECT OF TEMPERATURE ON THE SOUND ABSORPTION OF POROUS MATERIALS

Öz

The management of noise levels in various industrial products has led to the utilization of materials like foam and rockwool to achieve sound insulation. These materials serve the purpose of sound absorption and, in certain scenarios, facilitate the reduction of sound transmission within spaces where airflow is permitted. Moreover, they play a crucial role in optimizing sound transmission quality between speakers and listeners within conference halls. While these applications are significant, an equally crucial consideration is how these materials respond to varying temperature conditions within enclosed spaces. The interplay between temperature, sound absorption, and the materials' properties forms the core of this investigation. In environments where machinery operates within confined spaces, the release of heat and subsequent temperature increase can profoundly impact the sound absorption coefficient of materials. This phenomenon stems from alterations in both the physical characteristics of materials and the properties of the surrounding air as temperatures shift. To comprehensively study this phenomenon, the Miki model, Delany-Bazley model, ANSYS finite element analysis, and empirical impedance tube tests have been employed. The Miki model and Delany-Bazley model have been cornerstones in predicting sound absorption coefficients of fibrous and porous materials. By defining relationships between characteristic impedance and propagation constants, these models enable approximations of sound absorption coefficients based on properties like density and porosity. However, while these models provide insightful predictions, their accuracy rests on various assumptions, such as the negligible impact of temperature changes on material structure. The aim of this study is to examine the validity of these assumptions by subjecting them to rigorous empirical and numerical testing. Finite element analysis conducted through ANSYS software has been instrumental in verifying the mathematical predictions of sound absorption coefficients. This analysis involves manipulating variables like cylinder diameter and wavelength to ensure adequate resolution for accurate simulations. Such simulations shed light on the complex interactions between material properties, structure, and temperature. To further validate these numerical findings, empirical impedance tube tests were performed, adhering to ISO and ASTM standards. These tests provide empirical evidence of sound absorption coefficients under varying temperature conditions, serving as benchmarks for comparison with mathematical predictions. The outcomes of this research are multifaceted. Firstly, they reveal the interconnectedness of sound absorption coefficients, temperature, and material properties. The proposition that temperature changes insignificantly affect material behavior, except for the variations in dynamic viscosity and density of air, has been examined in detail. The study indicates that this proposition is reasonably accurate under the conditions tested, with test results closely aligning with mathematical predictions. Additionally, the research underscores the reliability of the Miki model and Delany-Bazley model, as these mathematical approximations closely match both numerical simulations and empirical test results. Practically, these findings hold substantial implications. In various industries, from generators to household appliances, the behavior of materials under changing temperature conditions is crucial for design and operational considerations. The study's conclusions suggest that the initial mathematical predictions and finite element analyses have a significant degree of universality. These insights can guide product design and operational strategies across diverse climates and thermal conditions. This study aims to illuminate the intricate relationship between temperature, sound absorption, and material properties. By combining mathematical modeling, finite element analysis, and empirical testing, it highlights the interplay of these factors and offers practical insights into the behavior of porous materials under changing temperature conditions. The results validate the accuracy of mathematical predictions, confirming their utility in diverse contexts. Ultimately, this research contributes to the optimization of noise control strategies across various industrial sectors.

Anahtar Kelimeler

• absorption coefficient
• porous materials
• temperature effect

SICAKLIĞIN GÖZENEKLİ MALZEMELERİN SES YUTUM KATSAYISI ÜZERİNDEKİ ETKİSİ

Öz

Günümüzde gürültü seviyesinin düşük olması istenen birçok endüstriyel üründe ses yalıtımı amacıyla sünger, taş yünü vb. malzeme kullanılmaktadır. Bu malzemeler sadece ses yutum amacıyla kullanılabileceği gibi bazı durumlarda hava akışına izin verilen bir boşlukta ses iletimini düşürmek amacıyla da kullanılabilmektedir. Bu malzemelerin bir diğer kullanım alanı ise konferans salonlarında konuşmacı ile dinleyiciler arsındaki ses iletim kalitesini en yüksek seviyeye taşımaktır. Bütün bu kullanım amaçlarının yanı sıra bu tip malzemelerin, kapalı bir kabin ya da oda içerisindeki değişken sıcaklık koşullarında nasıl davranış göstereceği önemli bir konudur. Kapalı bir ortam içerisindeki bir makinenin çalışması durumunda ortama yayılan ısı ve meydana gelen sıcaklık artışı ses yutum katsayısı üzerinde etkili olabilmektedir. Malzeme ve ortamda bulunan havanın fiziksel özelliklerinin sıcaklık artışı ile değişmesi ses yutum katsayısının da değişmesine neden olabilmektedir. Bu çalışmada, sıcaklık değişiminin süngerin ses yutum katsayısı üzerindeki etkisi Miki modeli, Delany-Bazley modeli, ANSYS sonlu elemanlar analiz modeli ve empedans tüpü ile deneysel olarak incelenmiştir.

Anahtar Kelimeler

• ses yutum katsayısı
• gözenekli akustik malzemeler
• sıcaklık etkisi

Kaynakça

1. ISO. (1998). ISO 10534-2:1998 Acoustics — Determination of sound absorption coefficient and impedance in impedance tubes — Part 2: Transfer-function method.
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9. Arjunan, A., Wang, C.J., Yahiaoui, K., Mynors, D.J., Morgan, T., Nguyen, V.B., ve English, M. (2014). Sound frequency dependent mesh modelling to simulate the acoustic insulation of stud based double-leaf walls. Proceedings of the 2014 Leuven Conference on Noise and Vibration Engineering (ISMA2014).
10. ASTM E1050. (2019). Standard Test Method for Impedance and Absorption of Acoustical Materials Using a Tube, Two Microphones and a Digital Frequency Analysis System.