MyMedR

Displaying publications 1 - 20 of 189 in total

Abstract:

Sort:

Fulltext Digital Filtering Techniques for Performance Improvement of Golay Coded TDM-FBG Sensor

Elgaud MM, Zan MSD, Abushagur AAG, Hamzah AE, Mokhtar MHH, Arsad N, et al.

Sensors (Basel), 2021 Jun 23;21(13).
PMID: 34201845 DOI: 10.3390/s21134299

For almost a half-decade, the unique autocorrelation properties of Golay complementary pairs (GCP) have added a significant value to the key performance of conventional time-domain multiplexed fiber Bragg grating sensors (TDM-FBGs). However, the employment of the unipolar form of Golay coded TDM-FBG has suffered from several performance flaws, such as limited improvement of the signal-to-noise ratio (SNIR), noisy backgrounds, and distorted signals. Therefore, we propose and experimentally implement several digital filtering techniques to mitigate such limitations. Moving averages (MA), Savitzky-Golay (SG), and moving median (MM) filters were deployed to process the signals from two low reflectance FBG sensors located after around 16 km of fiber. The first part of the experiment discussed the sole deployment of Golay codes from 4 bits to 256 bits in the TDM-FBG sensor. As a result, the total SNIR of around 8.8 dB was experimentally confirmed for the longest 256-bit code. Furthermore, the individual deployment of MA, MM, and SG filters within the mentioned decoded sequences secured a further significant increase in SNIR of around 4, 3.5, and 3 dB, respectively. Thus, the deployment of the filtering technique alone resulted in at least four times faster measurement time (equivalent to 3 dB SNIR). Overall, the experimental analysis confirmed that MM outperformed the other two techniques in better signal shape, fastest signal transition time, comparable SNIR, and capability to maintain high spatial resolution.

Matched MeSH terms: Signal-To-Noise Ratio*
Fulltext Identification of Noise Levels for Skill Training Activities, Equipment, Machines and Power Tools at TVET Institutes in Malaysia

Abdul Rahim KA, Jewaratnam J, Che Hassan CR

Int J Environ Res Public Health, 2022 Nov 27;19(23).
PMID: 36497858 DOI: 10.3390/ijerph192315783

The use of various machines, equipment and power tools at TVET Institute causes the institute's environment to be exposed to noise hazards that are similar to the industry. However, not much data has been published regarding noise exposure at TVET institutes. This study was carried out to document the noise exposure of work activities training in public TVET institutes in Malaysia that implement skill training programs in metal fabrication, furniture manufacturing and automotive maintenance. The identification of excessive noise, task-based noise exposure monitoring and source measurement was conducted. The noise contribution from each work activity to the daily A-weighted noise exposure level and sound pressure level emitted by machines and equipment was documented. The findings of this study recorded 20 activities with task-based noise contribution to the daily A-weighted noise exposure level between 75.3 dB and 95 dB. Based on the findings, the training environment at the TVET institutes has a risk of operating with excessive noise. The documented data can be used in planning the implementation of suitable noise control measures in TVET institutes.

Matched MeSH terms: Noise; Noise, Occupational*
Fulltext A vision of the environmental and occupational noise pollution in Malaysia

Yuen FK

Noise Health, 2014 Nov-Dec;16(73):427-36.
PMID: 25387540 DOI: 10.4103/1463-1741.144429

Environmental noise remains a complex and fragmented interplay between industrialization, population growth, technological developments, and the living environment. Next to the circulatory diseases and cancer, noise pollution has been cited as the third epidemic cause of psychological and physiological disorders internationally. A reliable and firm relationship between the cumulative health implications with the traffic annoyance and occupational noise has been established. This agenda has called for an integrated, coordinated, and participatory approach to the reliable protection of noise interference. Despite several fragmented policies, legislation and global efforts have been addressed; the noise pollution complaints have been traditionally neglected in developing countries, especially in Malaysia. This paper was undertaken to postulate an initial platform to address the dynamic pressures, gigantic challenges, and tremendous impacts of noise pollution scenario in Malaysia. The emphasis is speculated on the traffic interference and assessment of industrial and occupational noise. The fundamental importance of noise monitoring and modeling is proposed. Additionally, the confronting conservation program and control measure for noise pollution control are laconically elucidated.

Matched MeSH terms: Noise/adverse effects; Noise/legislation & jurisprudence; Noise/prevention & control; Noise, Occupational/adverse effects; Noise, Occupational/legislation & jurisprudence; Noise, Occupational/prevention & control*; Noise, Transportation/adverse effects; Noise, Transportation/legislation & jurisprudence; Noise, Transportation/prevention & control*
Fulltext Improving the dynamic characteristics of body-in-white structure using structural optimization

Yahaya Rashid AS, Ramli R, Mohamed Haris S, Alias A

ScientificWorldJournal, 2014;2014:190214.
PMID: 25101312 DOI: 10.1155/2014/190214

The dynamic behavior of a body-in-white (BIW) structure has significant influence on the noise, vibration, and harshness (NVH) and crashworthiness of a car. Therefore, by improving the dynamic characteristics of BIW, problems and failures associated with resonance and fatigue can be prevented. The design objectives attempt to improve the existing torsion and bending modes by using structural optimization subjected to dynamic load without compromising other factors such as mass and stiffness of the structure. The natural frequency of the design was modified by identifying and reinforcing the structure at critical locations. These crucial points are first identified by topology optimization using mass and natural frequencies as the design variables. The individual components obtained from the analysis go through a size optimization step to find their target thickness of the structure. The thickness of affected regions of the components will be modified according to the analysis. The results of both optimization steps suggest several design modifications to achieve the target vibration specifications without compromising the stiffness of the structure. A method of combining both optimization approaches is proposed to improve the design modification process.

Matched MeSH terms: Noise*
Fulltext Development of a voice activity controlled noise canceller

Abid Noor AO, Samad SA, Hussain A

Sensors (Basel), 2012;12(5):6727-45.
PMID: 22778667 DOI: 10.3390/s120506727

In this paper, a variable threshold voice activity detector (VAD) is developed to control the operation of a two-sensor adaptive noise canceller (ANC). The VAD prohibits the reference input of the ANC from containing some strength of actual speech signal during adaptation periods. The novelty of this approach resides in using the residual output from the noise canceller to control the decisions made by the VAD. Thresholds of full-band energy and zero-crossing features are adjusted according to the residual output of the adaptive filter. Performance evaluation of the proposed approach is quoted in terms of signal to noise ratio improvements as well mean square error (MSE) convergence of the ANC. The new approach showed an improved noise cancellation performance when tested under several types of environmental noise. Furthermore, the computational power of the adaptive process is reduced since the output of the adaptive filter is efficiently calculated only during non-speech periods.

Matched MeSH terms: Noise; Signal-To-Noise Ratio
Fulltext An innovations-based noise cancelling technique on inverse kepstrum whitening filter and adaptive FIR filter in beamforming structure

Jeong J

Sensors (Basel), 2011;11(7):6816-41.
PMID: 22163987 DOI: 10.3390/s110706816

This paper presents an acoustic noise cancelling technique using an inverse kepstrum system as an innovations-based whitening application for an adaptive finite impulse response (FIR) filter in beamforming structure. The inverse kepstrum method uses an innovations-whitened form from one acoustic path transfer function between a reference microphone sensor and a noise source so that the rear-end reference signal will then be a whitened sequence to a cascaded adaptive FIR filter in the beamforming structure. By using an inverse kepstrum filter as a whitening filter with the use of a delay filter, the cascaded adaptive FIR filter estimates only the numerator of the polynomial part from the ratio of overall combined transfer functions. The test results have shown that the adaptive FIR filter is more effective in beamforming structure than an adaptive noise cancelling (ANC) structure in terms of signal distortion in the desired signal and noise reduction in noise with nonminimum phase components. In addition, the inverse kepstrum method shows almost the same convergence level in estimate of noise statistics with the use of a smaller amount of adaptive FIR filter weights than the kepstrum method, hence it could provide better computational simplicity in processing. Furthermore, the rear-end inverse kepstrum method in beamforming structure has shown less signal distortion in the desired signal than the front-end kepstrum method and the front-end inverse kepstrum method in beamforming structure.

Matched MeSH terms: Noise*
Fulltext A stochastic simulation framework for the prediction of strategic noise mapping and occupational noise exposure using the random walk approach

Han LM, Haron Z, Yahya K, Bakar SA, Dimon MN

PLoS One, 2015;10(4):e0120667.
PMID: 25875019 DOI: 10.1371/journal.pone.0120667

Strategic noise mapping provides important information for noise impact assessment and noise abatement. However, producing reliable strategic noise mapping in a dynamic, complex working environment is difficult. This study proposes the implementation of the random walk approach as a new stochastic technique to simulate noise mapping and to predict the noise exposure level in a workplace. A stochastic simulation framework and software, namely RW-eNMS, were developed to facilitate the random walk approach in noise mapping prediction. This framework considers the randomness and complexity of machinery operation and noise emission levels. Also, it assesses the impact of noise on the workers and the surrounding environment. For data validation, three case studies were conducted to check the accuracy of the prediction data and to determine the efficiency and effectiveness of this approach. The results showed high accuracy of prediction results together with a majority of absolute differences of less than 2 dBA; also, the predicted noise doses were mostly in the range of measurement. Therefore, the random walk approach was effective in dealing with environmental noises. It could predict strategic noise mapping to facilitate noise monitoring and noise control in the workplaces.

Matched MeSH terms: Noise, Occupational*
Fulltext SNR improvements in self-heterodyne detection technique for laser linewidth measurements

Manimaran, R., Abdul-Rashid, H.A.

ASM Science Journal, 2008;2(2):133-137.
MyJurnal

This paper proposes a signal-to-noise-ratio (SNR) improvement by using an external phase modulator that allowed flexible control of the spectrum amplitude by varying the modulation index for linewidth measurements. Compared with the conventional self-heterodyne detection technique, the results obtained in this study showed an SNR improvement as high as 10 dB. This 10 dB improvement in SNR could help to reduce the usage of a particular length of a single mode fibre (normally about 50 Km) when measuring a linewidth in the region of 10 kHz.

Matched MeSH terms: Noise; Signal-To-Noise Ratio
A new algorithm to estimate attenuation using frequency shift methods

Maman Hermana, Hammad Hazim Mohd Azhar, Zuhar Zahir Tuan Harith

Sains Malaysiana, 2012;41:953-959.

This paper presents the improvement of quality factor (Q) estimation using shift frequency method. A new method was developed based on two previous methods; peak frequency shift (PFS) method and centroid frequency shift (CFS) method. The proposed algorithm has been tested to gauge its performance using three different scenarios; Q variation, travel
time variation, and signal to noise ratio (SNR) variation. The test was performed using the Ricker wavelet with random noise included. Based on the results obtained, it can be concluded that the new proposed method was able to improve Q estimation using shift frequency method. This method can also be implemented in the low and high Q condition, shallow and deep wavelet targets and in the low and high SNR conditions of seismic data. The limitations in the PFS and CFS methods can be reduced by this method.

Matched MeSH terms: Noise; Signal-To-Noise Ratio
The synthesis and decomposition of signals and its application in subei basin exploration

Xiangsheng Bao, Quanwen Liu, Haiyan Zhou

Sains Malaysiana, 2017;46:2169-2177.

Subei basin is the most promising onshore oil and gas bearing basin in South China. With the deepening of exploration, subtle hydrocarbon reservoirs have gradually become the major target of exploration. Seismic record often shows low signal to noise ratio (SNR), resulting that conventional seismic records have three shortcomings in the identification of subtle reservoirs: difficult to identify small faults; difficult to show the distribution law of sand body; and difficult to find traps. In order to solve this problem, we conducted the research on signal synthesis and decomposition. The research results showed that seismic record of different frequency bands can be restored from original seismic record and both of them contain real stratigraphic information. Based on this, when a certain band or several bands in the original seismic record is affected by noise and result in the reduction of SNR of seismic record, seismic information seriously affected by noise can be abandoned, leaving only less affected seismic information to obtain seismic record with higher SNR. In the collection of actual seismic record, the low and high band seismic information is seriously affected by noise, while medium-band seismic information is less affected. Therefore, based on this, the medium-band seismic information can be restored from the original seismic record to be new record, which is called predominant frequency band seismic record. In this paper, based on the research result, the predominant frequency band seismic record was applied to the two areas of Subei basin and the result showed the research result can be used as a good instruction on well placement and the improvement of drilling success rate.

Matched MeSH terms: Noise; Signal-To-Noise Ratio
Comparison of continuous sampling with active noise cancelation and sparse sampling for cortical and subcortical auditory functional MRI

Dewey RS, Hall DA, Plack CJ, Francis ST

Magn Reson Med, 2021 11;86(5):2577-2588.
PMID: 34196020 DOI: 10.1002/mrm.28902

PURPOSE: Detecting sound-related activity using functional MRI requires the auditory stimulus to be more salient than the intense background scanner acoustic noise. Various strategies can reduce the impact of scanner acoustic noise, including "sparse" temporal sampling with single/clustered acquisitions providing intervals without any background scanner acoustic noise, or active noise cancelation (ANC) during "continuous" temporal sampling, which generates an acoustic signal that adds destructively to the scanner acoustic noise, substantially reducing the acoustic energy at the participant's eardrum. Furthermore, multiband functional MRI allows multiple slices to be collected simultaneously, thereby reducing scanner acoustic noise in a given sampling period.
METHODS: Isotropic multiband functional MRI (1.5 mm) with sparse sampling (effective TR = 9000 ms, acquisition duration = 1962 ms) and continuous sampling (TR = 2000 ms) with ANC were compared in 15 normally hearing participants. A sustained broadband noise stimulus was presented to drive activation of both sustained and transient auditory responses within subcortical and cortical auditory regions.
RESULTS: Robust broadband noise-related activity was detected throughout the auditory pathways. Continuous sampling with ANC was found to give a statistically significant advantage over sparse sampling for the detection of the transient (onset) stimulus responses, particularly in the auditory cortex (P < .001) and inferior colliculus (P < .001), whereas gains provided by sparse over continuous ANC for detecting offset and sustained responses were marginal (p ~ 0.05 in superior olivary complex, inferior colliculus, medial geniculate body, and auditory cortex).
CONCLUSIONS: Sparse and continuous ANC multiband functional MRI protocols provide differing advantages for observing the transient (onset and offset) and sustained stimulus responses.

Matched MeSH terms: Noise*
Noise variance estimation using image noise cross-correlation model on SEM images

Sim KS, Nia ME, Tso CP

Scanning, 2013 May-Jun;35(3):205-12.
PMID: 22961698 DOI: 10.1002/sca.21055

A number of techniques have been proposed during the last three decades for noise variance and signal-to-noise ratio (SNR) estimation in digital images. While some methods have shown reliability and accuracy in SNR and noise variance estimations, other methods are dependent on the nature of the images and perform well on a limited number of image types. In this article, we prove the accuracy and the efficiency of the image noise cross-correlation estimation model, vs. other existing estimators, when applied to different types of scanning electron microscope images.

Matched MeSH terms: Noise; Signal-To-Noise Ratio
Image noise cross-correlation for signal-to-noise ratio estimation in scanning electron microscope images

Sim KS, Nia ME, Tso CP

Scanning, 2011 Mar-Apr;33(2):82-93.
PMID: 21381045 DOI: 10.1002/sca.20223

A new and robust parameter estimation technique, named image noise cross-correlation, is proposed to predict the signal-to-noise ratio (SNR) of scanning electron microscope images. The results of SNR and variance estimation values are tested and compared with nearest neighborhood and first-order interpolation. Overall, the proposed method is best as its estimations for the noise-free peak and SNR are most consistent and accurate to within a certain acceptable degree, compared with the others.

Matched MeSH terms: Noise; Signal-To-Noise Ratio
Image signal-to-noise ratio estimation using Shape-Preserving Piecewise Cubic Hermite Autoregressive Moving Average model

Sim KS, Wee MY, Lim WK

Microsc Res Tech, 2008 Oct;71(10):710-20.
PMID: 18615490 DOI: 10.1002/jemt.20610

We propose to cascade the Shape-Preserving Piecewise Cubic Hermite model with the Autoregressive Moving Average (ARMA) interpolator; we call this technique the Shape-Preserving Piecewise Cubic Hermite Autoregressive Moving Average (SP2CHARMA) model. In a few test cases involving different images, this model is found to deliver an optimum solution for signal to noise ratio (SNR) estimation problems under different noise environments. The performance of the proposed estimator is compared with two existing methods: the autoregressive-based and autoregressive moving average estimators. Being more robust with noise, the SP2CHARMA estimator has efficiency that is significantly greater than those of the two methods.

Matched MeSH terms: Signal-To-Noise Ratio
Fulltext Two-Level Scheduling for Video Transmission over Downlink OFDMA Networks

Tham ML, Chow CO, Xu YH, Ramli N

PLoS One, 2016;11(2):e0148625.
PMID: 26906398 DOI: 10.1371/journal.pone.0148625

This paper presents a two-level scheduling scheme for video transmission over downlink orthogonal frequency-division multiple access (OFDMA) networks. It aims to maximize the aggregate quality of the video users subject to the playback delay and resource constraints, by exploiting the multiuser diversity and the video characteristics. The upper level schedules the transmission of video packets among multiple users based on an overall target bit-error-rate (BER), the importance level of packet and resource consumption efficiency factor. Instead, the lower level renders unequal error protection (UEP) in terms of target BER among the scheduled packets by solving a weighted sum distortion minimization problem, where each user weight reflects the total importance level of the packets that has been scheduled for that user. Frequency-selective power is then water-filled over all the assigned subcarriers in order to leverage the potential channel coding gain. Realistic simulation results demonstrate that the proposed scheme significantly outperforms the state-of-the-art scheduling scheme by up to 6.8 dB in terms of peak-signal-to-noise-ratio (PSNR). Further test evaluates the suitability of equal power allocation which is the common assumption in the literature.

Matched MeSH terms: Signal-To-Noise Ratio
Fulltext Susceptibility to Residual Inhibition Is Associated With Hearing Loss and Tinnitus Chronicity

Hu S, Anschuetz L, Hall DA, Caversaccio M, Wimmer W

Trends Hear, 2021 3 6;25:2331216520986303.
PMID: 33663298 DOI: 10.1177/2331216520986303

Residual inhibition, that is, the temporary suppression of tinnitus loudness after acoustic stimulation, is a frequently observed phenomenon that may have prognostic value for clinical applications. However, it is unclear in which subjects residual inhibition is more likely and how stable the effect of inhibition is over multiple repetitions. The primary aim of this work was to evaluate the effect of hearing loss and tinnitus chronicity on residual inhibition susceptibility. The secondary aim was to investigate the short-term repeatability of residual inhibition. Residual inhibition was assessed in 74 tinnitus subjects with 60-second narrow-band noise stimuli in 10 consecutive trials. The subjects were assigned to groups according to their depth of suppression (substantial residual inhibition vs. comparator group). In addition, a categorization in normal hearing and hearing loss groups, related to the degree of hearing loss at the frequency corresponding to the tinnitus pitch, was made. Logistic regression was used to identify factors associated with susceptibility to residual inhibition. Repeatability of residual inhibition was assessed using mixed-effects ordinal regression including poststimulus time and repetitions as factors. Tinnitus chronicity was not associated with residual inhibition for subjects with hearing loss, while a statistically significant negative association between tinnitus chronicity and residual inhibition susceptibility was observed in normal hearing subjects (odds ratio: 0.63; p = .0076). Moreover, repeated states of suppression can be stably induced, reinforcing the use of residual inhibition for within-subject comparison studies.

Matched MeSH terms: Noise
Fulltext Monitoring noise level during Sukhoi aircraft operation at no. 11 Squadron

Mohd Rizal Hamid, Ahmad Faruq Mohamad Rosli, Manokaran, Kesavan, Siti Shafiqa Shamira Hashin, Nik Mohd Dzarrin Ghifari Azmy, Baba Md Deros, et al.

ZULFAQAR International Journal of Defence Science, Engineering & Technology, 2020;3(2):25-31.
MyJurnal

Awareness of occupational noise and its effects is growing. At No. 11 squadron base, Sukhoi jet was identified as the main culprit of occupational noise that affects not just the employees of the base but also civilian people in the surrounding area. The objective of the study is to identify the noise level produced by Sukhoi two-engines jet during maintenance operations. Investigations were carried out using Bruel & Kjaer 2250 sound level meter hand-analyser. Measurements were performed directly under the Sukhoi jet body and then 10 metres, 50 metres, 100 metres, 1000 metres and 1500 metres away. The jet engines could operate at two levels, at 72% RPM and at 85% RPM. The civilians are only exposed to its noise from more than 1000 metres away. The results from this study are analysed and noise mapping and noise contouring are produced which give the level of noise exposure. The maximum noise is recorded t 122dB(A) and the minimum is at 60dB(A). The farther the noise from the jet is measured, the lower the values recorded. From the noise mapping, the effects of noise exposures on both the employees at the base and the civilian at the neighbouring surrounding could be identified. Even though the exposures are only for 5-10 minutes, it is still considered as a threat

Matched MeSH terms: Noise, Occupational
Fulltext Ambient noise reduction using improved least mean square adaptive filtering

Noor, A.O.A., Samad, S.A., Hussain, A.

ASM Science Journal, 2010;4(2):133-141.
MyJurnal

In this paper, an improved method of reducing ambient noise in speech signals is introduced. The proposed noise canceller was developed using a computationally efficient (DFT) filter bank to decompose input signals into sub-bands. The filter bank was based on a prototype filter optimized for minimum output distortion. A variable step-size version of the (LMS) filter was used to reduce the noise in individual branches. The subband noise canceller was aimed to overcome problems associated with the use of the conventional least mean square (LMS) adaptive algorithm in noise cancellation setups. Mean square error convergence was used as a measure of performance under white and ambient interferences. Compared to conventional as well as recently developed techniques, fast initial convergence and better noise cancellation performances were obtained under actual speech and ambient noise.

Matched MeSH terms: Noise
Fulltext Improved architecture of speaker recognition based on wavelet transform and Mel Frequency Cepstral Coefficient (MFCC)

Nor Ashikin Rahman, Noor Azilah Muda, Norashikin Ahmad

Pertanika Journal of Science & Technology, 2017;25(106):1-10.
MyJurnal

Combining Mel Frequency Cepstral Coefficient with wavelet transform for feature extraction is not new. This paper proposes a new architecture to help in increasing the accuracy of speaker recognition compared with conventional architecture. In conventional speaker model, the voice will undergo noise elimination first before feature extraction. The proposed architecture however, will extract the features and eliminate noise simultaneously. The MFCC is used to extract the voice features while wavelet de-noising technique is used to eliminate the noise contained in the speech signals. Thus, the new architecture achieves two outcomes in one single process: ex-tracting voice feature and elimination of noise.

Matched MeSH terms: Noise
Beamforming technique for investigation of lateral variability at geotechnical sites

Norfarah Nadia Ismail, Joh SH, Raja Hassanul Musa Raja Ahmad

Sains Malaysiana, 2012;41:1621-1627.

A beamformer in seismology is a signal receptor with a series of geophones, in which a beam of elastic waves is formed like a light beam by adjusting signal delays at individual geophones. Recently, beamforming has extended its applications to surface-wave measurement. In surface-wave measurement, beamforming provides unique advantages over other surface-wave methods, such as full automation in data analysis as well as directional signal reception to minimize scattered noise and multiple reflections in signals. However, certain defects depreciate the value of beamforming in terms of its practicality and feasibility. These include the requirement of having many receivers and the loss of small wavelength data due to spatial aliasing. It leads to insensitivity in identification of lateral variability, which creates the problem of having to smooth out geologic features and complexities like folding, faults and fractures. In this paper, advances in the refinement of beamforming were described on two counts: improvement of sensitivity in identification of lateral variability and recovery of aliased wave numbers, which enables evaluation of shallow material. On the passage to refinement, synthetic waveforms for typical layering systems were generated to figure out characteristics of beamformer velocities in comparison with SASW velocities and theoretical normal-mode velocities.

Matched MeSH terms: Noise

Filters

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links