In this paper the influence of non-acoustic properties on the sound absorption coefficient of polyurethane foams as a porous medium is investigated. Biot’s equations with transfer matrix method, as the solution approach are employed to evaluate the sound absorption coefficient of selected polyurethane foams. The major issue is the dependency of non-acoustic properties on each other which makes ...

My devotion never translates to my fingers.There is something lost.The scaly chaff of heart opens lungs.I pinch pic like a quillwhat can I scrawl in the dusk?The eighth notes scream as harmonizeendless Ds without uA whittler stripping block's clotheskeeping time at arm's lengthdesperate for revelation.Em Am7 G D6 D. The progression eternal.I believe delicate vice on fretcalluses encroaching pri...

In an environment such as underwater channel where placing test equipments are difficult to handle, it is much practical to have hardware simulators to examine suitably designed transceivers (transmitter/receiver). The simulators of this kind will then allow researchers to observe their intentions and carry out repetitive tests to find suitable digital coding/decoding algorithms. In this p...

Composites have been widely used in the aerospace industry. Due to the requirement of a high safety for such structures, they could be considered for health monitoring. The acoustic emission approach is one of most effective methods for identifying damages in composites. In this article, standard specimens were made from carbon fibers and the epoxy resin, with the [03/902/...

A theoretical study analyzing three-dimensional combustion acoustic instabilities in a liquid propellant rocket engine combustor has been conducted. A linear theory based on Crocco’s pressure sensitive time lag model is used. To apply this theory the combustor is divided into two main components, including the combustion chamber and the converging part of the nozzle. The assumption of concentra...

This paper reports the results of an experimental study on non-native production of English vowels. Two groups of Persian EFL learners varying in language proficiency were tested on their ability to produce the nine plain vowels of American English. Vowel production accuracy was assessed by means of acoustic measurements. Ladefoged and Maddison’s (1996) F1 F2 measurements for American English v...