Musli Nizam Yahya

Comparison between GLCM and modified Zernike moments for material surfaces identification from photo images

Types of materials are one of an important data for research in acoustic engineering. This paper compares methods for extracting texture data of material surfaces for classification. Gray Level Co-occurrence Matrix (GLCM) and modified Zernike moments that is applied for image extraction are tested and compared with back propagation neural network used for classification. These methods are also applied to the Brodatz texture database as a general comparison. The GLCM method shows a good performance and regression, R>0.9 for the Brodatz database while the collected surfaces datasets using GLCM and modified Zernike moments as well as the Brodatz datasets using modified Zernike moments method had only managed an acceptable performance and regression of R>0.8.

A Preliminary Study on Acoustical Performance of Oil Palm Mesocarp Natural Fiber

As the population increases, the demand of a comfortable environmental such as sound pollution is getting higher. Sound pollutions also have become worsen and creating concerns for many peoples. Due to this problem, synthetic materials as acoustic absorbers still applied as commonly acoustical panels and this material may hazardous to human health and contribute significantly a pollution to the environments. However, researchers have interested in conducting their research on natural fiber to be an alternative sound absorber. This study investigated the potential of oil palm Mesocarp fiber for sound absorbing material. The Mesocarp fibers were mixed with polyurethane (PU) as binder with ratio of 70:30. The thickness was varied in 10mm, 20mm, 30mm, and 40mm. This study also investigated the air gap of 5mm and 10mm in the sound absorption performance. Impedance Tube Method was used to measure sound absorption coefficient (a). The measurement was done on accordance with ASTM E1050-98, which is the standard test method for impedance and absorption of acoustical materials using a tube. The results showed that the optimum value for Mesocarp fiber is 0.93. The optimum value obtained at 5000 Hz. The influence of air gap increases the sound absorption especially from 250 Hz to 4000 Hz. These results indicate that fiber from Mesocarp is promising to be used sound absorbing material.

A Platform for Digital Reproduction Sound of Traditional Musical Instrument Kompang

This work proposes a system for the digital reproduction sound of kompang. The kompang sounds are represented by bung and pak produced by palm beating to the membrane. The sounds are recorded in an acoustical sound recording system. In this proposed system, the recorded sounds are then analyzed in a frequency analyzer SpectraPLUS. This frequency contents data can be used as the reference to check the reproduced digital sound. The recorded wave data is converted to MIDI format before being manipulated in Ableton synthesizer system to create modern keyboard notes but representing kompang sound. For the validation purpose, a subjective approach as an additional to the objective comparison with frequency contents is also proposed.

Hybrid Bat-BP: A New Intelligent Tool for Diagnosing Noise-Induced Hearing Loss (NIHL) in Malaysian Industrial Workers

Noise-Induced Hearing Loss (NIHL) has become a major health threat to the Malaysian industrial workers in the recent era due to exposure to high frequency noise produced by the heavy machines. Recently, many studies have been conducted to diagnose the NIHL in industrial workers but unfortunately they neglected some factors that can play a major role in speeding-up NIHL. In this paper, a new Hybrid Bat-BP algorithm which is based on the trio combination of BAT based metaheuristic optimization, back-propagation neural network, and fuzzy logic is proposed to diagnose NIHL in Malaysian industrial workers. The proposed Hybrid Bat-BP will use heat, body mass index (BMI), diabetes, and smoking along with the century old audiometric variables (i.e. age, frequency, and duration of exposure) to better predict NIHL in Malaysian workers. The results obtained through Hybrid Bat-BP will be able to help us identify and reduce the NIHL rate in the workers with high accuracy.

The Acoustical Characteristics Analysis on Different Type of Natural Fibres

Natural fibres are fibre that can be directly obtained from an animal, mineral, or vegetable sources. Recently natural materials are becoming a good alternative for synthetic material as they provide good health to a greener environment. This aim of this study to investigate and compared the acoustic characteristics of three natural fibres; Kenaf fibre (Hibiscus Cannabinus), Ijuk fibre (Arenga Pinnata), and Coconut coir fibre, where each material is qualified for acoustical absorption. During the processing stage, each fibre is reinforced with 60:40 ratio of pure latex separately. The fibres are then compressed after the pure latex treatment into circular samples, of 28 mm and 100 mm diameters respectively. The thickness of each sample is fixed at 50mm. The acoustical performances were evaluated by using an impedance tube instrument. This study also investigates the effect of air gap of 10mm and 50mm in the sound absorption performance. The results show that, all the three fibres have reached an optimum level of sound absorption value of more than 0.7. The frequency peak value of Kenaf is obtained in a range of 700 Hz – 800 Hz, while for coconut coir is at 1000 Hz – 1075 Hz frequency range. Only Ijuk has obtained the highest frequency range of 3200 Hz – 3400 Hz. The results demonstrate that these three fibres are a promising light and environment-friendly sound absorption material as they are ready to replace the common synthetic fibre.

Hand-arm vibration disorder among grass-cutter workers in Malaysia.

Introduction. Prolonged exposure to hand-transmitted vibration from grass-cutting machines has been associated with increasing occurrences of symptoms and signs of occupational diseases related to hand–arm vibration syndrome (HAVS). Methods. A cross-sectional study was carried out using an adopted HAVS questionnaire on hand–arm vibration exposure and symptoms distributed to 168 male workers from the grass and turf maintenance industry who use hand-held grass-cutting machines as part of their work. The prevalence ratio and symptom correlation to HAVS between high and low–moderate exposure risk groups were evaluated. Results. There were positive HAVS symptoms relationships between the low–moderate exposure group and the high exposure group among hand-held grass-cutting workers. The prevalence ratio was considered high because there were indicators that fingers turned white and felt numb, 3.63, 95% CI [1.41, 9.39] and 4.24, 95% CI [2.18, 8.27], respectively. Less than 14.3% of workers stated that they were aware of the occupational hand–arm vibration, and it seemed to be related to the finger blanching and numbness. Conclusion. The results suggest that HAVS is under-diagnosed in Malaysia, especially in the agricultural sectors. More information related to safety and health awareness programmes for HAVS exposure is required among hand-held grass-cutting workers.

Prediction of Classroom Reverberation Time using Neural Network

In this paper, an alternative method for predicting the reverberation time (RT) using neural network (NN) for classroom was designed and explored. Classroom models were created using Google SketchUp software. The NN applied training dataset from the classroom models with RT values that were computed from ODEON 12.10 software. The NN was conducted separately for 500Hz, 1000Hz, and 2000Hz as absorption coefficient that is one of the prominent input variable is frequency dependent. Mean squared error (MSE) and regression (R) values were obtained to examine the NN efficiency. Overall, the NN shows a good result with MSE < 0.005 and R > 0.9. The NN also managed to achieve a percentage of accuracy of 92.53% for 500Hz, 93.66% for 1000Hz, and 93.18% for 2000Hz and thus displays a good and efficient performance. Nevertheless, the optimum RT value is range between 0.75 – 0.9 seconds

Optimization of Sound Absorbers Number and Placement in an Enclosed Room by Finite Element Simulation

Giving a room proper acoustic treatment is both art and science. Acoustic design brings comfort in the built environment and reduces noise level by using sound absorbers. There is a need to give a room acoustic treatment by installing absorbers in order to decrease the reverberant sound. However, they are usually high in price which cost much for installation and there is no system to locate the optimum number and placement of sound absorbers. It would be a waste if the room is overly treated with absorbers or cause improper treatment if the room is treated with insufficient absorbers. This study aims to determine the amount of sound absorbers needed and optimum location of sound absorbers placement in order to reduce the overall sound pressure level in specified room by using ANSYS APDL software. The size of sound absorbers needed is found to be 11

Modelling of Rigid Walled Enclosure Couple to a Flexible Wall using Matlab and Ansys APDL

Generally, solutions to improve the noise problems in enclosure are to redesign or modifying the system such as increasing the thickness of the wall panels, enhancing the elasticity of the structure, and increase the damping mechanism of the wall structure. In this paper, the application of vibroacoustic modelling of enclosure coupled to a flexible wall was presented. The sound pressure characteristics of rigid walled enclosure, such as natural frequency and mode shape were determined using two approaches which are finite element simulation of Ansys® and mathematical model. The mathematical equations derived in Matlab® such as rigid walled enclosure and rigid walled enclosure coupled to flexible wall were used to validate finite element analysis (FEA). The result indicates that the theory and FEA display in a good agreement. Thus, proved that the FE model was accurate and can be applied in further research such as sound pressure and noise attenuation in enclosure.

A Review on the Potential of Natural Fibre for Sound Absorption Application

This review covers an alternative material known as natural fibre that can be used to replace synthetic fibre as core material for the production of sound absorber. The review explored natural fibre such as bamboo fibre, arenga pinnata, paddy straw fibre, oil palm mesocarp fibre, and kenaf fibre in terms of acoustic properties such as sound absorption coefficient. It has been found that plenty of research regarding the utilization of natural fibre for sound absorption purposes have been accomplished. The implementation of natural fibre in producing sound absorber brings many environmental benefit as it is much greener compared to existing material such as synthetic fibre. Apart from that, natural fibre does not impose any serious health effect compared to the existing synthetic fibre.