Uncertainties Consideration in Empirical Frequency Response Function Data for Damage Identification Based On Artificial Neural Network

The modern application of frequency response function (FRF) with artificial neural networks (ANN) has become one of the leading methods in vibration-based damage detection approach. However, since full-size empirically obtained FRF data is used as ANN input, a broad composition ANN input layer series would occur. Consequently, principal component analysis (PCA) is adopted to compress the FRF data magnitude. Despite this, PCA alone is unable to select the important FRF data features effectively, due to the exceedingly FRF data size in addition with existing uncertainties. Therefore, this study proposed the merger of a non-probabilistic analysis and ANN approach with PCA by considering the uncertainties effect and the inefficiency of using empirical FRF data. The empirical FRF data is obtained from a steel truss bridge structure. The results show that the PoDE values above 95% are measured at the particular executed damage locations and the DMI values show the damage severity at the actual damage locations. Overall, the results show that the proposed method is capable in considering the uncertainties effect on the empirical FRF data for structural damage identification

Palm Oil Clinker as Noise Control Materials

Palm oil clinker (POC) is a waste from the production process of palm oil, a hard and porous materials. Many studies have focused on the effect of POC use on strength while this study discusses the ability of POC in concrete to absorb sound and its relationship with concrete properties. The study was done by replacing natural river sand in stages of 25, 50, 75 and 100 percent in a mixture of 1: 4 (cement: sand). Sound absorption coefficient (SAC), strength and physical properties affect the SAC were measured. Although POC significantly reduced the compressive strength but all specimens poses good strength more than 5 N/mm2. An interesting result is that POC reduces interconnected porosity and total porosity when replacement is 100% but increases interconnected and total porosity when replacement is between 50 and 75%. SAC at 315 Hz was found has good relationship with percentage of POC and density. It is obtained that POC 50% yield good strength and sufficient SAC that can address the middle frequency range problem, thus can be further suggested to be used for masonry block application for noise control materials

A prototyping model of intelligent hearing protection device

The occupational noise exposure problem is getting serious and the workers have low self-efficacy in using the hearing protectors during the working period. In this paper, it reveals a prototyping model, namely, Intelligent Hearing Protection Device (IHPD) as a new hearing technology to cope with current problems. This device could measure the noise level in the workplace, detect the regularity of worker in the usage of IHPD and indicate the high noise area. Meanwhile, the IHPD is required to connect with the Dosiwatch and the Integrated Noise Exposure Software (INES) to improve its functionalities. The Dosiwatch is an electronic device to display the noise level and indicate the risky area, where it helps the workers to perceive the risk of noise in a workplace. The INES receives the noise data wirelessly, plots the instantaneous noise charts and supervises the regularity of workers in using the IHPD. By the way, the technical procedure development and the typical function of electronic gadgets are significant in this invention. A prototyping model was developed to ensure the technical procedure development meets the conceptual design of IHPD, dosiwatch and INES

Construction noise annoyance among the public residents

Construction activities generate construction noise may cause noise annoyance among the public residents. The aim of this study is to investigate the noise annoyance level due to the sound pressure levels and the distances from the construction sites. Three public resident areas around Johor which located near to the construction sites have been selected. Two important indicators such as sound pressure levels and distances between the receiver and the noise sources were measured. 42 questionnaires were randomly distributed to the public residents who live near to the construction sites. The results showed that all respondent have different annoyance levels due to the construction noise. The sound pressure levels received by the public residents are increasing with the decreasing of the distance between the receiver and the noise sources. Thus, the relationship of noise annoyance levels is directly proportional to the sound pressure levels produced from construction sites. Meanwhile, the noise annoyance levels are decreasing with the increasing of the distances. As a conclusion, the public residents who live nearer to the construction sites suffered from a high noise annoyance level as expected

The potential of napier grass leaf fibres as an acoustic absorber

Acoustic absorbers are introduced to treat poor acoustic enviroment in rooms. However, many available acoustic absorbers in the market are composed of hazardous materials. Therefore, there are demands for the use of sustainable materials in the production of acoustic absorbers. This research investigated the sound absorption potential of grass leaf fibres, i.e. Napier grass, as material for acoustic absorbers. Various bound Napier grass fibre samples, with and without binder under normal press with different thickness, were prepared and tested by using an impedance tube test for sound absorption coefficient (SAC) determination. Samples with binder under hot press with thickness of 10mm were also prepared. The results revealed that 5mm and 20mm fibres, respectively, when bonded with urea formaldhyde (UF) under normal press and with thickness of 30mm, produced a relatively high SAC for frequencies at 500 Hz, 1000 Hz and 2500 Hz, and thus resulted in a high average NRC value of 0.59. This exceeded the value for synthetic fibre-glass and was similar to rockwool. Moreover, the sound absorption performance of 20 mm fibre size hot pressed samples were better than hot pressed 5mm fibre size at 500 Hz frequency until 1000 Hz, as well as the bulk and fibre bonded with UF samples for all frequencies. This study concluded that non-toxic Napier grass fibres can be used in the production of sustainable acoustic absorbers

A preliminary study of environmental noise in public university

Environmental noise problems have increased every year and have brought negative effects to the neighbouring communities. Educational areas, such as university, college and school, are the places for learning and gaining knowledge. However, students feel stressed and annoyed when they are exposed to noisy environments. The main objective of this research is to investigate the current environmental noise problem in Universiti Teknologi Malaysia (UTM). It is a preliminary study of environmental noise problem and a total of 24 measurement locations were selected based on the working zones in UTM. Each location was measured in an hour during the working period. About 95.8 percent of the measurement results exceeded the permissible limit of the guideline by the Department of Environment (DOE). Besides, the UTM noise zones have been established by referring to the measurement results. The findings of this study could assist the UTM management in deciding the noise abatement strategy. Also, the noise zones could be disseminated to the public in order to increase the public awareness towards the environmental noise problems in UTM

A preliminary study of occupational noise exposure among leaf blower and grass cutter workers in public university

Many occupational noise exposure studies have been conducted in various occupational sectors. However, in Malaysia, there are limited numbers of study on grass cutter workers and there is no study on leaf blower workers. Thus, this preliminary study was conducted to assess both occupational noise exposure among leaf blower and grass cutter workers by measuring occupational noise exposure, determining sound power level of the machines and conducting interview session. A total of 20 workers were selected from a public university as study subjects. Noise dosimeter and sound level meter were used to measure the occupational noise exposure and sound pressure level of all machines in determining their sound power levels respectively. Most of the workers were exposed to daily noise dose and time-weighted average (TWA) noise level which exceed the permissible limits. All machines recorded a high sound power level and several workers showed prevalence symptoms of hearing loss. This preliminary study revealed that most of the workers are exposed to excessive occupational noise exposure and at high risk of acquiring noise-induced hearing loss (NIHL)

'Serene classroom' minimizes noise for more conducive learning

Noise pollution can be categorized as a danger in silence. In school, noise pollution inhibits the focus of learning, impairs learning and cognitive development, for example, students' skills to think and understand both oral and written comprehension may be hampered by noise. Many schools in Malaysia experience excessive noise pollution as their locations are very near busy roads. This will be one factor that hinders the implementation of the education system in producing holistic students in order to prepare for the 4IR era. Knowing the importance of this problem, a group of researchers from UTM GREENPrompt, School of Civil Engineering, Universiti Teknologi Malaysia together with industry partners have built a special class called 'Serene Classroom' through a community project to overcome this problem. A classroom on the second floor of Sekolah Kebangsaan Kampong Pasir, Johor Bahru that has traffic noise exposure from the Skudai-Johor Bahru highway was selected for this purpose. The community project is in collaboration with the Johor State Education Department, Ministry of Education Malaysia and industrial partners, such as Vibrant Echo Company, Sanjung Sempurna Sdn. Bhd. and DZAZ Collection. The implementation of the project, the lessons learned from the project and challenges for the implementation are discussed. Technically, Serene classrooms significantly reduce the level of noise pollution for more conducive learning and have received better perceptions from students and teachers. Therefore, hopefully more ‘Serene Classroom’ community projects can be implemented in schools, especially in urban areas affected by high noise levels as a way to reduce the renovation costs on schools

Noise prediction and measurement from construction sites

Construction industry is one of the contributors to economic growth and it has the highest tendency to generate noise. Construction noise becomes one of the main sources of noise pollution which affect the public and construction workers. Construction noise prediction at planning stage must be carried out and prepared through Environmental Impact Assessment (EIA). There are various methods of construction noise prediction that have been practiced by the respected parties. The British Standards Institution (BSI) and the Department of Environment (DOE) have published BS 5228 – Part 1: 2009 – Code of Practice for Noise and Vibration Control on Construction and Open Sites and The Planning Guidelines for Environmental Noise Limits and Control respectively. These standards and guidelines were usually be used by the respected parties since currently, there are no specific established noise prediction method. However, previous researches were claimed BS 5228 – Part 1: 2009 procedures as inaccurate due to several factors. Thus, this study was carried out to evaluate the disparity of results between construction noise predictions using BS 5228 – Part 1: 2009 procedures and real on-site noise measurements. The objectives of this study are to obtain noise levels from construction sites, to predict noise levels from construction sites and to evaluate the disparity between these two results. The real on-site noise measurements were conducted at three selected construction sites with different stages of construction. Meanwhile, construction noise predictions were calculated using BS 5228 – Part 1: 2009 procedures. The disparity of the results was evaluated using statistical test in Statistical Package for Social Sciences (SPSS) software. The results of one sample T-test show the significant differences between these two results. The disparity might due to several affecting factors such as atmospheric and geometrical factors, operation conditions, periods and powers and work schedules of construction activities

Acoustical characteristic changes due to transverse rumble strips installation on roadway

Transverse rumble strips (TRS) acts as a traffic calming device to alert inattentive drivers through the optical, sound and vibration effects. Currently, the existing TRS guidelines have been found to be very basic with no detailed explanation on the TRS profile. Inappropriate design of TRS profile may generate excessive external noise level that can affect the nearby residents. Besides, the real cause of TRS roadside noise annoyance is still unknown. Therefore, this study aims to evaluate the acoustical characteristic changes due to TRS installation at residential areas in contributing to the framework of optimum TRS design selection for future installation. The objectives of this study are to investigate current TRS designs and characteristics, determine road and traffic characteristics at selected roadways, evaluate noise annoyance due to TRS installation and develop empirical model of TRS roadside noise level for the proposal of framework of optimum TRS design selection. Visual investigation and on-site measurement were conducted to investigate the current TRS design and characteristic. Measurement of road and traffic measurements were also carried out to evaluate the skid number (SN), vehicle speed, traffic volume and composition that may affect sound level changes. This study measured the external noise generated by a range of gross vehicle weight (GVW) between 850 kg and 7700 kg which travel over three types of TRS, namely middle overlapped (MO), middle layer overlapped (MLO) and raised rumbler (RR) with speed range of between 30 km/h to 70 km/h. Controlled pass-by (CPB) method was conducted to determine the sound level changes. Actual traffic condition due to TRS installation was also measured. Meanwhile, assessment of sound level changes and impulse, low frequency noise (LFN) and tonal, noise limit and traffic noise index (TNI) were carried out to assess the noise annoyance from TRS. Statistical analyses were used to test all related variables of roadside noise level due to TRS. Significant variables were used for the development of empirical noise models by using multiple linear regression. Then, framework of optimum TRS selection design was proposed to assist local authorities for future TRS installation. TRS thickness was limited to 3 mm for all profile types. TRS roadside noise may affect nearby residents as the sound level increment was more than 6 dBA. The sound level changes for vehicles transit on MLO were higher than MO and RR of more and less than 3 dBA, respectively. Besides, MLO showed the most significant impulsivity regardless of the multiple vehicles transit. TRS roadside noise was also characterized by LFN at frequency region of 20 Hz to 125 Hz. Tonality was also found significant especially due to heavier vehicles with GVW of 5000 kg and above at speed of 50 km/h. Among the three types of TRS, MO showed the best performance due to its insignificant acoustical characteristics. SN, vehicle speed, traffic volume and GVW were found to be significant variable for the generation of TRS roadside noise level. Meanwhile, other variables, such as TRS width, length, spacing, profile and strip number, traffic volume and skid resistance were found insignificant. The established empirical models based on the real causes of TRS noise annoyance were used in the proposal for framework of optimum TRS design selection for future installation. This proposed framework could enable exploration of TRS impact on the traffic noise condition to facilitate the local authority on the best selection of TRS type during the surround area become critical for noise annoyance