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Effects of background noise on recording of portable transient-evoked otoacoustic emission in newborn hearing screening

Salina H, Abdullah A, Mukari SZ, Azmi MT

Eur Arch Otorhinolaryngol, 2010 Apr;267(4):495-9.
PMID: 19727788 DOI: 10.1007/s00405-009-1080-y

Transient-evoked otoacoustic emission (TEOAE) is a well-established screening tool for universal newborn hearing screening. The aims of this study are to measure the effects of background noise on recording of TEOAE and the duration required to complete the test at various noise levels. This study is a prospective study from June 2006 until May 2007. The study population were newborns from postnatal wards who were delivered at term pregnancy. Newborns who were more than 8-h old and passed a hearing screening testing using screening auditory brainstem response (SABRe) were further tested with TEOAE in four different test environments [isolation room in the ward during non-peak hour (E1), isolation room in the ward during peak hour (E2), maternal bedside in the ward during non-peak hour (E3) and maternal bedside in the ward during peak hour (E4)]. This study showed that test environment significantly influenced the time required to complete testing in both ears with F [534.23] = 0.945; P < 0.001 on the right ear and F [636.54] = 0.954; P < 0.001 on the left. Our study revealed that TEOAE testing was efficient in defining the presence of normal hearing in our postnatal wards at maternal bedside during non-peak hour with a specificity of 96.8%. Our study concludes that background noise levels for acceptable and accurate TEOAE recording in newborns should not exceed 65 dB A. In addition, when using TEOAE assessment in noisy environments, the time taken to obtain accurate results will greatly increase.

Matched MeSH terms: Noise*
Fulltext New regression model for predicting hand-arm vibration (HAV) of Malaysian Army (MA) three-tonne truck steering wheels

Aziz SA, Nuawi MZ, Nor MJ

J Occup Health, 2015;57(6):513-20.
PMID: 26269278 DOI: 10.1539/joh.14-0206-OA

OBJECTIVE: The objective of this study was to present a new method for determination of hand-arm vibration (HAV) in Malaysian Army (MA) three-tonne truck steering wheels based on changes in vehicle speed using regression model and the statistical analysis method known as Integrated Kurtosis-Based Algorithm for Z-Notch Filter Technique Vibro (I-kaz Vibro).
METHODOLOGY: The test was conducted for two different road conditions, tarmac and dirt roads. HAV exposure was measured using a Brüel & Kjær Type 3649 vibration analyzer, which is capable of recording HAV exposures from steering wheels. The data was analyzed using I-kaz Vibro to determine the HAV values in relation to varying speeds of a truck and to determine the degree of data scattering for HAV data signals.
RESULTS: Based on the results obtained, HAV experienced by drivers can be determined using the daily vibration exposure A(8), I-kaz Vibro coefficient (Ƶ(v)(∞)), and the I-kaz Vibro display. The I-kaz Vibro displays also showed greater scatterings, indicating that the values of Ƶ(v)(∞) and A(8) were increasing. Prediction of HAV exposure was done using the developed regression model and graphical representations of Ƶ(v)(∞). The results of the regression model showed that Ƶ(v)(∞) increased when the vehicle speed and HAV exposure increased.
DISCUSSION: For model validation, predicted and measured noise exposures were compared, and high coefficient of correlation (R(2)) values were obtained, indicating that good agreement was obtained between them. By using the developed regression model, we can easily predict HAV exposure from steering wheels for HAV exposure monitoring.

Matched MeSH terms: Noise, Occupational/statistics & numerical data
Fulltext Cortical signal-in-noise coding varies by noise type, signal-to-noise ratio, age, and hearing status

Maamor N, Billings CJ

Neurosci Lett, 2017 01 01;636:258-264.
PMID: 27838448 DOI: 10.1016/j.neulet.2016.11.020

The purpose of this study was to determine the effects of noise type, signal-to-noise ratio (SNR), age, and hearing status on cortical auditory evoked potentials (CAEPs) to speech sounds. This helps to explain the hearing-in-noise difficulties often seen in the aging and hearing impaired population. Continuous, modulated, and babble noise types were presented at varying SNRs to 30 individuals divided into three groups according to age and hearing status. Significant main effects of noise type, SNR, and group were found. Interaction effects revealed that the SNR effect varies as a function of noise type and is most systematic for continuous noise. Effects of age and hearing loss were limited to CAEP latency and were differentially modulated by energetic and informational-like masking. It is clear that the spectrotemporal characteristics of signals and noises play an important role in determining the morphology of neural responses. Participant factors such as age and hearing status, also play an important role in determining the brain's response to complex auditory stimuli and contribute to the ability to listen in noise.

Matched MeSH terms: Signal-To-Noise Ratio*
Noise-induced hearing loss and associated factors among vector control workers in a Malaysian state

Masilamani R, Rasib A, Darus A, Ting AS

Asia Pac J Public Health, 2014 Nov;26(6):642-50.
PMID: 22548779 DOI: 10.1177/1010539512444776

This study aims to determine the prevalence and associated factors of noise-induced hearing loss (NIHL) among vector control workers in the state of Negeri Sembilan, Malaysia. This was an analytical cross-sectional study conducted on 181 vector control workers who were working in district health offices in a state in Malaysia. Data were collected using a self-administered questionnaire and audiometry. Prevalence of NIHL was 26% among this group of workers. NIHL was significantly associated with the age-group of 40 years and older, length of service of 10 or more years, current occupational noise exposure, listening to loud music, history of firearms use, and history of mumps/measles infection. Following logistic regression, age of more than 40 years and noise exposure in current occupation were associated with NIHL with an odds ratio of 3.45 (95% confidence interval = 1.68-7.07) and 6.87 (95% confidence interval = 1.54-30.69), respectively, among this group of vector control workers.

Matched MeSH terms: Hearing Loss, Noise-Induced/epidemiology*
Vitamin E attenuates nicotine- and noise-induced reproductive impairment in male albino Wistar rats

Bisong SA, Ukoh IE, Nna VU, Ebong PE

Andrologia, 2018 Sep;50(7):e13050.
PMID: 29806220 DOI: 10.1111/and.13050

Previous studies showed that exposure to stress or nicotine induced reproductive impairment in male rats. Here, we assessed the effect of an antioxidant (vitamin E) on nicotine-, stress- and nicotine + stress-induced reproductive impairment in male rats. Forty-eight male albino Wistar rats were divided into eight groups as follows; control, stress (generator noise 90-120 dB, 8 hr/day), nicotine (1.5 mg kg-1 day-1 ), nicotine + stress, vitamin E (100 mg kg-1 day-1 ), stress + vitamin E, nicotine + vitamin E and stress + nicotine + vitamin E. Sperm count, viability, motility and rapid progressive forward movement decreased significantly (p

Matched MeSH terms: Noise/adverse effects
Fulltext The association between subcortical and cortical fMRI and lifetime noise exposure in listeners with normal hearing thresholds

Dewey RS, Francis ST, Guest H, Prendergast G, Millman RE, Plack CJ, et al.

Neuroimage, 2020 Jan 01;204:116239.
PMID: 31586673 DOI: 10.1016/j.neuroimage.2019.116239

In animal models, exposure to high noise levels can cause permanent damage to hair-cell synapses (cochlear synaptopathy) for high-threshold auditory nerve fibers without affecting sensitivity to quiet sounds. This has been confirmed in several mammalian species, but the hypothesis that lifetime noise exposure affects auditory function in humans with normal audiometric thresholds remains unconfirmed and current evidence from human electrophysiology is contradictory. Here we report the auditory brainstem response (ABR), and both transient (stimulus onset and offset) and sustained functional magnetic resonance imaging (fMRI) responses throughout the human central auditory pathway across lifetime noise exposure. Healthy young individuals aged 25-40 years were recruited into high (n = 32) and low (n = 30) lifetime noise exposure groups, stratified for age, and balanced for audiometric threshold up to 16 kHz fMRI demonstrated robust broadband noise-related activity throughout the auditory pathway (cochlear nucleus, superior olivary complex, nucleus of the lateral lemniscus, inferior colliculus, medial geniculate body and auditory cortex). fMRI responses in the auditory pathway to broadband noise onset were significantly enhanced in the high noise exposure group relative to the low exposure group, differences in sustained fMRI responses did not reach significance, and no significant group differences were found in the click-evoked ABR. Exploratory analyses found no significant relationships between the neural responses and self-reported tinnitus or reduced sound-level tolerance (symptoms associated with synaptopathy). In summary, although a small effect, these fMRI results suggest that lifetime noise exposure may be associated with central hyperactivity in young adults with normal hearing thresholds.

Matched MeSH terms: Noise/adverse effects*
Fulltext Multi-level basis selection of wavelet packet decomposition tree for heart sound classification

Safara F, Doraisamy S, Azman A, Jantan A, Abdullah Ramaiah AR

Comput Biol Med, 2013 Oct;43(10):1407-14.
PMID: 24034732 DOI: 10.1016/j.compbiomed.2013.06.016

Wavelet packet transform decomposes a signal into a set of orthonormal bases (nodes) and provides opportunities to select an appropriate set of these bases for feature extraction. In this paper, multi-level basis selection (MLBS) is proposed to preserve the most informative bases of a wavelet packet decomposition tree through removing less informative bases by applying three exclusion criteria: frequency range, noise frequency, and energy threshold. MLBS achieved an accuracy of 97.56% for classifying normal heart sound, aortic stenosis, mitral regurgitation, and aortic regurgitation. MLBS is a promising basis selection to be suggested for signals with a small range of frequencies.

Matched MeSH terms: Signal-To-Noise Ratio
Fulltext Tamper localization and lossless recovery watermarking scheme with ROI segmentation and multilevel authentication

Liew SC, Liew SW, Zain JM

J Digit Imaging, 2013 Apr;26(2):316-25.
PMID: 22555905 DOI: 10.1007/s10278-012-9484-4

Tamper localization and recovery watermarking scheme can be used to detect manipulation and recover tampered images. In this paper, a tamper localization and lossless recovery scheme that used region of interest (ROI) segmentation and multilevel authentication was proposed. The watermarked images had a high average peak signal-to-noise ratio of 48.7 dB and the results showed that tampering was successfully localized and tampered area was exactly recovered. The usage of ROI segmentation and multilevel authentication had significantly reduced the time taken by approximately 50 % for the tamper localization and recovery processing.

Matched MeSH terms: Signal-To-Noise Ratio
Fulltext Acoustic cardiac signals analysis: a Kalman filter-based approach

Salleh SH, Hussain HS, Swee TT, Ting CM, Noor AM, Pipatsart S, et al.

Int J Nanomedicine, 2012;7:2873-81.
PMID: 22745550 DOI: 10.2147/IJN.S32315

Auscultation of the heart is accompanied by both electrical activity and sound. Heart auscultation provides clues to diagnose many cardiac abnormalities. Unfortunately, detection of relevant symptoms and diagnosis based on heart sound through a stethoscope is difficult. The reason GPs find this difficult is that the heart sounds are of short duration and separated from one another by less than 30 ms. In addition, the cost of false positives constitutes wasted time and emotional anxiety for both patient and GP. Many heart diseases cause changes in heart sound, waveform, and additional murmurs before other signs and symptoms appear. Heart-sound auscultation is the primary test conducted by GPs. These sounds are generated primarily by turbulent flow of blood in the heart. Analysis of heart sounds requires a quiet environment with minimum ambient noise. In order to address such issues, the technique of denoising and estimating the biomedical heart signal is proposed in this investigation. Normally, the performance of the filter naturally depends on prior information related to the statistical properties of the signal and the background noise. This paper proposes Kalman filtering for denoising statistical heart sound. The cycles of heart sounds are certain to follow first-order Gauss-Markov process. These cycles are observed with additional noise for the given measurement. The model is formulated into state-space form to enable use of a Kalman filter to estimate the clean cycles of heart sounds. The estimates obtained by Kalman filtering are optimal in mean squared sense.

Matched MeSH terms: Signal-To-Noise Ratio
Medial olivocochlear functioning and speech perception in noise in older adults

Mukari SZ, Mamat WH

Audiol. Neurootol., 2008;13(5):328-34.
PMID: 18460868 DOI: 10.1159/000128978

The purposes of this study were to: (1) compare medial olivocochlear system (MOCS) functioning and speech perception in noise in young and older adults and (2) to quantify the correlation between MOCS functioning and speech perception in noise. Measurements were taken in 20 young (mean 26.3 +/- 2.1 years) and 20 older adults (mean 55.2 +/- 2.8 years). Contralateral distortion product otoacoustic emission (DPOAE) suppression was measured to assess MOCS functioning. Speech perception in noise was evaluated using the Hearing in Noise Test in noise-ipsilateral, noise-front and noise-contralateral test conditions. The results revealed that the older group had a significantly lower high-frequency (3-8 kHz) contralateral DPOAE suppression, and performed more poorly in the noise-ipsilateral condition than the younger group. However, there was no correlation between contralateral DPOAE suppression and speech perception in noise. This study suggests that poor speech perception performance in noise experienced by older adults might be due to a decline in medial olivocochlear functioning, among other factors.

Matched MeSH terms: Noise
An expectation-maximization algorithm based Kalman smoother approach for single-trial estimation of event-related potentials

Ting CM, Samdin SB, Salleh ShH, Omar MH, Kamarulafizam I

Annu Int Conf IEEE Eng Med Biol Soc, 2012;2012:6534-8.
PMID: 23367426 DOI: 10.1109/EMBC.2012.6347491

This paper applies an expectation-maximization (EM) based Kalman smoother (KS) approach for single-trial event-related potential (ERP) estimation. Existing studies assume a Markov diffusion process for the dynamics of ERP parameters which is recursively estimated by optimal filtering approaches such as Kalman filter (KF). However, these studies only consider estimation of ERP state parameters while the model parameters are pre-specified using manual tuning, which is time-consuming for practical usage besides giving suboptimal estimates. We extend the KF approach by adding EM based maximum likelihood estimation of the model parameters to obtain more accurate ERP estimates automatically. We also introduce different model variants by allowing flexibility in the covariance structure of model noises. Optimal model selection is performed based on Akaike Information Criterion (AIC). The method is applied to estimation of chirp-evoked auditory brainstem responses (ABRs) for detection of wave V critical for assessment of hearing loss. Results shows that use of more complex covariances are better estimating inter-trial variability.

Matched MeSH terms: Signal-To-Noise Ratio
Correlation between subjective and objective assessment of magnetic resonance (MR) images

Chow LS, Rajagopal H, Paramesran R, Alzheimer's Disease Neuroimaging Initiative

Magn Reson Imaging, 2016 07;34(6):820-831.
PMID: 26969762 DOI: 10.1016/j.mri.2016.03.006

Medical Image Quality Assessment (IQA) plays an important role in assisting and evaluating the development of any new hardware, imaging sequences, pre-processing or post-processing algorithms. We have performed a quantitative analysis of the correlation between subjective and objective Full Reference - IQA (FR-IQA) on Magnetic Resonance (MR) images of the human brain, spine, knee and abdomen. We have created a MR image database that consists of 25 original reference images and 750 distorted images. The reference images were distorted with six types of distortions: Rician Noise, Gaussian White Noise, Gaussian Blur, DCT compression, JPEG compression and JPEG2000 compression, at various levels of distortion. Twenty eight subjects were chosen to evaluate the images resulting in a total of 21,700 human evaluations. The raw scores were then converted to Difference Mean Opinion Score (DMOS). Thirteen objective FR-IQA metrics were used to determine the validity of the subjective DMOS. The results indicate a high correlation between the subjective and objective assessment of the MR images. The Noise Quality Measurement (NQM) has the highest correlation with DMOS, where the mean Pearson Linear Correlation Coefficient (PLCC) and Spearman Rank Order Correlation Coefficient (SROCC) are 0.936 and 0.938 respectively. The Universal Quality Index (UQI) has the lowest correlation with DMOS, where the mean PLCC and SROCC are 0.807 and 0.815 respectively. Student's T-test was used to find the difference in performance of FR-IQA across different types of distortion. The superior IQAs tested statistically are UQI for Rician noise images, Visual Information Fidelity (VIF) for Gaussian blur images, NQM for both DCT and JPEG compressed images, Peak Signal-to-Noise Ratio (PSNR) for JPEG2000 compressed images.

Matched MeSH terms: Signal-To-Noise Ratio
Ergonomic study on the manual component insertion lines for occupational health and safety improvements

Sen RN, Yeow PH

Int J Occup Saf Ergon, 2003;9(1):57-74.
PMID: 12636892

The study aimed at reducing the occupational health and safety problems faced by the manual component insertion operators. Subjective and objective assessments, and direct observations were made in the printed circuit assembly factory. Simple and low-cost ergonomic interventions were implemented, that is, repairing chairs, reducing high workloads, assigning operators to a maximum of 2 workstations, confining machines that emitted bad smell and much noise, and providing finger work aids. The results of the interventions were reductions in operators' work discomforts, that is, chair discomfort (by 90%), high work stress, and discomfort due to profound change in their workstations. Their health hazards were also eliminated, that is, inhalation of toxic fumes, exposure to too much noise, and pain due to pressing sharp components.

Matched MeSH terms: Noise, Occupational
Fulltext Factors of job satisfaction among workers exposed to occupational noise

Irniza Rasdi, Noraini Mohd Zin, Sharifah Norkhadijah Syed Ismail

Malaysian Journal of Medicine and Health Sciences, 2019;15(204):141-146.
MyJurnal

Introduction: Noise was evident to reduce job satisfaction among workers which will negative impacts to workers including increase job turnover, decrease motivation and increased number of accidents. This study aims to explore job satisfaction and its risk factors among workers working in a noisy workplace. Method: The study design was cross-sectional study which involved 167 workers in a cable manufacturing factory selected by simple random sam- pling. MSQ was used to assess employee’s satisfaction with their job on seven facets and sound level meter was used to measure workplace noise level. Results: All respondents were exposed to noise above permissible exposure limit. Most workers (49%) were moderately satisfied with their work. Factors that were rated as lowest level of satisfaction were work itself (the ability to work alone) (40%) and the way company system policies are implemented (40%). Factors with the highest level of satisfaction were their freedom to implement their judgement (responsibility) (51%) and the supervision quality of their superiors (51%). The most dominant facet predicting total satisfaction level was recognition followed by advancement and company policy and administration. All variables in socio-demographical and job characteristics were not significantly associated with their level of job satisfaction except noise. Noise was significant in predicting one facet of job satisfaction which was physical work condition. Conclusion: Overall, the average level of job satisfaction among respondents were moderate and they were exposed to occupational noise which was the only significant study variable correlated with their job satisfaction.

Matched MeSH terms: Noise, Occupational
Fulltext Increasing iterative reconstruction strength at low tube voltage in coronary CT angiography protocols using 3D-printed and Catphan® 500 phantoms

Abdullah KA, McEntee MF, Reed WM, Kench PL

J Appl Clin Med Phys, 2020 Sep;21(9):209-214.
PMID: 32657493 DOI: 10.1002/acm2.12977

PURPOSE: The purpose of this study was to investigate the effect of increasing iterative reconstruction (IR) algorithm strength at different tube voltages in coronary computed tomography angiography (CCTA) protocols using a three-dimensional (3D)-printed and Catphan® 500 phantoms.
METHODS: A 3D-printed cardiac insert and Catphan 500 phantoms were scanned using CCTA protocols at 120 and 100 kVp tube voltages. All CT acquisitions were reconstructed using filtered back projection (FBP) and Adaptive Statistical Iterative Reconstruction (ASIR) algorithm at 40% and 60% strengths. Image quality characteristics such as image noise, signal-noise ratio (SNR), contrast-noise ratio (CNR), high spatial resolution, and low contrast resolution were analyzed.
RESULTS: There was no significant difference (P > 0.05) between 120 and 100 kVp measures for image noise for FBP vs ASIR 60% (16.6 ± 3.8 vs 16.7 ± 4.8), SNR of ASIR 40% vs ASIR 60% (27.3 ± 5.4 vs 26.4 ± 4.8), and CNR of FBP vs ASIR 40% (31.3 ± 3.9 vs 30.1 ± 4.3), respectively. Based on the Modulation Transfer Function (MTF) analysis, there was a minimal change of image quality for each tube voltage but increases when higher strengths of ASIR were used. The best measure of low contrast detectability was observed at ASIR 60% at 120 kVp.
CONCLUSIONS: Changing the IR strength has yielded different image quality noise characteristics. In this study, the use of 100 kVp and ASIR 60% yielded comparable image quality noise characteristics to the standard CCTA protocols using 120 kVp of ASIR 40%. A combination of 3D-printed and Catphan® 500 phantoms could be used to perform CT dose optimization protocols.

Matched MeSH terms: Signal-To-Noise Ratio
The outcomes of bilateral cochlear implant users in Universiti Kebangsaan Malaysia

Mohammad Azmi HH, Goh BS, Abdullah A, Umat C

Acta Otolaryngol, 2020 Oct;140(10):838-844.
PMID: 32564640 DOI: 10.1080/00016489.2020.1775887

INTRODUCTION: Bilateral cochlear implants are seen to improve hearing capabilities.
OBJECTIVE: To assess the auditory outcome of paediatric bilateral cochlear implant in Universiti Kebangsaan Malaysia.
MATERIALS AND METHODS: This was a cross-sectional and descriptive study single centre analysis. Categories of Auditory Performance (CAP-II) scale and Speech, Spatial and Qualities (SSQ) of Hearing questionnaire were used.
RESULTS: Forty-six patients were recruited. Majority of the children (30.4%) rated 7 and 23.9% scored perfectly (9) based on the CAP-II Scale. The least performing children were rated 5 (average). Children that were implanted sequentially within 24 months showed median CAP-II scale of 7. No significant correlation seen between CAP-II and the duration interval, use and age of 1st CI (p > .05). The speech domain of SSQ-P scale showed median value of 8 indicating good speech understanding. The spatial hearing domain had median value of 7, quality of hearing domain had median of 8. Significant correlation seen in hearing in noise with the duration of use of CI (p

Matched MeSH terms: Noise
Analysis of model-based and model-free CEST effect quantification methods for different medical applications

Foo LS, Yap WS, Hum YC, Manan HA, Tee YK

J Magn Reson, 2020 01;310:106648.
PMID: 31760147 DOI: 10.1016/j.jmr.2019.106648

Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) holds great potential to provide new metabolic information for clinical applications such as tumor, stroke and Parkinson's Disease diagnosis. Many active research and developments have been conducted to translate this emerging MRI technique for routine clinical applications. In general, there are two CEST quantification techniques: (i) model-free and (ii) model-based techniques. The reliability of these quantification techniques depends heavily on the experimental conditions and quality of the collected data. Errors such as noise may lead to misleading quantification results and thus inaccurate diagnosis when CEST imaging becomes a standard or routine imaging scan in the future. This paper investigates the accuracy and robustness of these quantification techniques under different signal-to-noise (SNR) levels and magnetic field strengths. The quantified CEST effect before and after adding random Gaussian White Noise using model-free and model-based quantification techniques were compared. It was found that the model-free technique consistently yielded larger average percentage error across all tested parameters compared to its model-based counterpart, and that the model-based technique could withstand SNR of about 3 times lower than the model-free technique. When applied on noisy brain tumor, ischemic stroke, and Parkinson's Disease clinical data, the model-free technique failed to produce significant differences between normal and abnormal tissue whereas the model-based technique consistently generated significant differences. Although the model-free technique was less accurate and robust, its simplicity and thus speed would still make it a good approximate when the SNR was high (>50) or when the CEST effect was large and well-defined. For more accurate CEST quantification, model-based techniques should be considered. When SNR was low (<50) and the CEST effect was small such as those acquired from clinical field strength scanners, which are generally 3T and below, model-based techniques should be considered over model-free counterpart to maintain an average percentage error of less than 44% even under very noisy condition as tested in this work.

Matched MeSH terms: Signal-To-Noise Ratio
Fulltext Automatic Artifact Removal in EEG of Normal and Demented Individuals Using ICA-WT during Working Memory Tasks

Al-Qazzaz NK, Hamid Bin Mohd Ali S, Ahmad SA, Islam MS, Escudero J

Sensors (Basel), 2017 Jun 08;17(6).
PMID: 28594352 DOI: 10.3390/s17061326

Characterizing dementia is a global challenge in supporting personalized health care. The electroencephalogram (EEG) is a promising tool to support the diagnosis and evaluation of abnormalities in the human brain. The EEG sensors record the brain activity directly with excellent time resolution. In this study, EEG sensor with 19 electrodes were used to test the background activities of the brains of five vascular dementia (VaD), 15 stroke-related patients with mild cognitive impairment (MCI), and 15 healthy subjects during a working memory (WM) task. The objective of this study is twofold. First, it aims to enhance the recorded EEG signals using a novel technique that combines automatic independent component analysis (AICA) and wavelet transform (WT), that is, the AICA-WT technique; second, it aims to extract and investigate the spectral features that characterize the post-stroke dementia patients compared to the control subjects. The proposed AICA-WT technique is a four-stage approach. In the first stage, the independent components (ICs) were estimated. In the second stage, three-step artifact identification metrics were applied to detect the artifactual components. The components identified as artifacts were marked as critical and denoised through DWT in the third stage. In the fourth stage, the corrected ICs were reconstructed to obtain artifact-free EEG signals. The performance of the proposed AICA-WT technique was compared with those of two other techniques based on AICA and WT denoising methods using cross-correlation X C o r r and peak signal to noise ratio ( P S N R ) (ANOVA, p ˂ 0.05). The AICA-WT technique exhibited the best artifact removal performance. The assumption that there would be a deceleration of EEG dominant frequencies in VaD and MCI patients compared with control subjects was assessed with AICA-WT (ANOVA, p ˂ 0.05). Therefore, this study may provide information on post-stroke dementia particularly VaD and stroke-related MCI patients through spectral analysis of EEG background activities that can help to provide useful diagnostic indexes by using EEG signal processing.

Matched MeSH terms: Signal-To-Noise Ratio
Effects of white noise on word recall performance and brain activity in healthy adolescents with normal and low auditory working memory

Othman E, Yusoff AN, Mohamad M, Abdul Manan H, Abd Hamid AI, Giampietro V

Exp Brain Res, 2020 Apr;238(4):945-956.
PMID: 32179941 DOI: 10.1007/s00221-020-05765-3

The present study examined the impact of white noise on word recall performance and brain activity in 40 healthy adolescents, split in two groups (normal and low) depending on their auditory working memory capacity (AWMC). Using functional magnetic resonance imaging, participants performed a backward recall task under four different signal-to-noise ratio (SNR) conditions: 15, 10, 5, and 0-dB SNR. Behaviorally, normal AWMC individuals scored significantly higher than low AWMC individuals across noise levels. Whole-brain analyses showed brain activation not to be statistically different between groups across noise levels. In the normal group, a significant positive relationship was found between performance and number of activated voxels in the right superior frontal gyrus. In the low group, significant positive correlations were found between performance and number of activated voxels in left superior frontal gyrus, left inferior frontal gyrus, and left anterior cingulate cortex. These findings suggest that the strategic structure involved in the enhancement of AWM performance may differ in normal and low AWMC individuals.

Matched MeSH terms: Noise
Reducing charging effects in scanning electron microscope images by Rayleigh contrast stretching method (RCS)

Wan Ismail WZ, Sim KS, Tso CP, Ting HY

Scanning, 2011 Jul-Aug;33(4):233-51.
PMID: 21611953 DOI: 10.1002/sca.20237

To reduce undesirable charging effects in scanning electron microscope images, Rayleigh contrast stretching is developed and employed. First, re-scaling is performed on the input image histograms with Rayleigh algorithm. Then, contrast stretching or contrast adjustment is implemented to improve the images while reducing the contrast charging artifacts. This technique has been compared to some existing histogram equalization (HE) extension techniques: recursive sub-image HE, contrast stretching dynamic HE, multipeak HE and recursive mean separate HE. Other post processing methods, such as wavelet approach, spatial filtering, and exponential contrast stretching, are compared as well. Overall, the proposed method produces better image compensation in reducing charging artifacts.

Matched MeSH terms: Signal-To-Noise Ratio

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