SOUND TRANSMISSION LOSS OF A DOUBLE-LEAF SOLID-MICROPERFORATED PARTITION UNDER NORMAL INCIDENCE OF ACOUSTIC LOADING

The micro-perforated panel (MPP) is recently well-known as an alternative ‘green‘ sound absorber replacing the conventional porous materials. Constructed from a solid panel which provides a non-abrassive structure and also an optically attractive surface, there gives a feasibility to implement such a panel inside a vehicle cabin. This paper is the preliminary study to investigate the sound transmission loss (TL) of a solid panel coupled with a micro-perforated panel to form a doube-leaf partition which is already known as a lightweigth stucture for noise insulation in vehicles and buildings. The mathematical model for the TL subjected to normal incidence of acoustic excitation is derived. The results show that its performance substantially improves at the troublesome frequency of mass-air-mass resonance which occurs in the conventional double-leaf solid partition. This is important particularly for the noise source predominant at low frequencies. This can also be controlled by tuning the hole size and number as well as the air gap between the panels.  ABSTRAK: Panel bertebuk mikro (micro-perforated panel (MPP)) kebelakangan ini dikenali sebagai alternatif penyerap bunyi yang mesra alam menggantikan bahan berliang lazim. Dibina daripada satu panel padu yang memberikan satu struktur tak lelas dan juga satu permukaan yang menarik, ia memberikan kemungkinan penggunaan panel tersebut di dalam kabin kenderaan. Tesis ini merupakan kajian permulaan dalam mengkaji hilang pancaran bunyi (sound transmission loss (TL)) oleh satu panel padu yang digandingkan dengan satu panel bertebuk mikro. Kaedah ini menghasilkan satu sekatan lembar kembar yang sememangnya dikenali sebagai struktur ringan penebat bunyi di dalam kenderaan dan bangunan. Model matematik diterbitkan untuk TL tersebut dengan menjalankan pengujaan akustik yang tuju normal. Keputusan menunjukkan bahawa prestasi meningkat dengan ketara pada frekuensi yang susah semasa resonans jisim-udara-jisim berlaku di dalam sekatan padu lembar kembar  lazim. Ini penting terutamanya untuk sumber bunyi yang pradominan pada frekuensi rendah. Ia juga boleh dikawal dengan menalakan saiz dan jumlah lubang serta luang udara di antara panel-panel  tersebut

A Bibliometric Analysis the Scope of Local, Global, And Glocal Studies

This article seeks to employ bibliometric analysis to offer a thorough picture of the research environment concerning local, global, and glocal contexts. Amidst the increasing globalization, it is imperative to deeply understand the interplay between local and global contexts and the "glocal" concept. This study investigates the current body of literature on these three areas by assessing patterns of publishing, trends in research, and collaborations among scientists. Using data from famous academic databases, we have found noteworthy keywords, notable authors, and esteemed publications pertaining to this topic. The research indicates a significant rise in the quantity of publications regarding local, global, and global contexts during the previous two decades. This research also illustrates a shift in focus from localized contextual examinations to a more inclusive approach that combines global and local perspectives. These findings are anticipated to offer scholars and practitioners a novel understanding of the dynamics of interaction between local, global, and glocal contexts. Moreover, these discoveries will be a significant reference for forthcoming investigations in this field

Comparative Study on the Kinematic Performance of Front Wheel Drive (FWD) and Rear Wheel Drive (RWD) Vehicles

The automotive industry has continuously innovated drive systems. Among various types, Front Wheel Drive (FWD) and Rear Wheel Drive (RWD) systems are widely used. This research examines the influence of these systems on acceleration and deceleration performance through field tests conducted on public highways. Five speed variations—40, 60, 80, 100, and 110 km/h—were tested for acceleration and deceleration. Results indicate RWD vehicles outperform FWD vehicles in acceleration due to the rear location of the drive wheels, providing superior propulsion. Conversely, FWD vehicles demonstrate better deceleration performance, attributed to shorter braking distances and improved braking efficiency

Comparison of the Fuel Consumption Performance of Rear and Front Wheel Drive Vehicles via Road Test

This paper presents an on-site investigation of a fuel consumption comparison between a Front Wheel Drive (FWD) and Rear Wheel Drive (RWD) vehicle as those are the two most common drive type used in the commercial vehicle. The study focuses on the fuel consumption rate by comparing the average distance achieved by one liter of fuel using the same type of engine. The road test was varied from the normal highway, uphill, downhill, as well as normal city road to give more insight about the fuel consumption characteristics of each variation. From the results, it is known that each road type gives significant different characteristics to the fuel consumption. Also, the comparison between FWD and RWD regarding fuel consumption gives interesting results for further vehicle transmission developments

Sound transmission loss of a double-leaf solid-microperforated partition under normal incidence of acoustic loading

One of the most considerable aspects of a vehicle design judged by the customers is the noise level inside the cabin. The conventional method is the use of absorbent materials as the noise absorber e.g. foam and other porous materials. These materials are usually made from synthetic and are therefore not environmentally friendly. Moreover, they can be easily dirty or damage and give bad odour due to smoke or moist. Since the microperforated panel (MPP) has been investigated to have a good performance as the sound absorber, there is a feasibility to implement such a panel inside a vehicle cabin. The MPP which is constructed from a solid panel will provide a hygienic and a non- abrasive material. Its optically attractive surface will also enhance the art in the cabin interior. However, the presence of holes will reduce the transmission loss performance which cannot be tolerated for a good noise barrier. This paper is the preliminary study to investigate the performance of a double-leaf solid and microperforated partition (SMPP) in terms of its sound transmission loss (STL). The mathematical model for the STL is derived. The result shows that the performance substantially improves at the troublesome frequency the so-called mass-air- mass resonance which occurs in the conventional double-leaf partition. This is important particularly for the noise source predominant at low frequencies. This can also be controlled by tuning the hole size and number as well as the air gap between the panels. However, above this frequency, the general performance of the STL is decreased

Interactive Module Development of Teacher's Measurements

This research develops an interactive module system that can be used to explore and build a self-assessment checklist on significant learning content in the daily life and work of students in the future. The purpose of this interactive module system is to contribute to the teacher in choosing the appropriate learning content for teaching. This study will focus on the contents of Form 1 history subjects involving teachers and students. In addition, with a self-assessment checklist of teachers, educators can use it in determining significant learning content with the life and nature of student work. The built-in interactive module system also benefits pupils when the learning takes place content and skills that can be used all the time. The data were obtained through field observations in the classroom and teacher work. In general, the use of interactive module systems developed is very good and effective. The findings show that the majority of users have stated that the developed system interface is of interest to the user, in which the navigation system developed is user-friendly. The user states that the usability of the developed system is very helpful to teachers and students in understanding the content of the given lessons

INSERTION OF A MICRO-PERFORATED PANEL TO IMPROVE SOUND TRANSMISSION LOSS OF A DOUBLE-LEAF PARTITION

Over decades a double-leaf partition in engineering structures has been widely applied for its advantages i.e. in terms of the mechanical strength and toughness as well as its lightweight property. For noise control application, the double-leaf has also been known to be an effective noise barrier. Unfortunately at resonance frequency, the sound transmission loss (TL) reduces significantly due to the coupling between the panels and the air between them. This paper investigates the effect of a micro-perforated panel (MPP) inserted inside a double-leaf partition to improve the TL performance at the troublesome resonance frequency of a conventional double-leaf structure. It is found that the TL improves at the resonance if the MPP is located closer to the solid panel. The mathematical model is derived for normal incidence of acoustic loading

SOUND TRANSMISSION LOSS OF A DOUBLE-LEAF PARTITION WITH MICRO-PERFORATED PLATE INSERTION UNDER DIFFUSE FIELD INCIDENCE

In noise control applications, a double-leaf partition has been applied widely as a lightweight structure for noise insulation, such as in car doors, train bodies, and aircraft fuselages. Unfortunately, the insulation performance deteriorates significantly at mass-air-mass resonance due to coupling between the panels and the air in the gap. This paper investigates the effect of a micro-perforated panel (MPP), inserted in the conventional double-panel partition, on sound transmission loss at troublesome resonant frequencies. It is found that the transmission loss improves at this resonance if the MPP is located at a distance of less than half that of the air gap. A mathematical model is derived for the diffuse field incidence of acoustic loading

Pemetaan Kebisingan pada Mesin CNC Milling Mini menggunakan Metode Time Waveform Analysis

This research aims to determine the characteristics of the noise produced by a mini CNC machine during operation at feeding speed of 50 mm/m, 100 mm/min, 150 mm/min, in several different materials with a constant feed depth of 0.5 mm. This research will provide initial information regarding the frequency and amplitude distribution (SPL) of noise which will be useful for planning appropriate noise barrier in the future in industry. By processing the noise data produced from the voice recorder and sound meter level using the waveform method, the results obtained shows that the highest noise values is from a feeding speed of 100 mm/min with an SPL of 86 dB.