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Dimakopoulos V, Neidert MC, Sarnthein J. Low impedance electrodes improve detection of high frequency oscillations in the intracranial EEG. Clin Neurophysiol 2023; 153:133-140. [PMID: 37487419 DOI: 10.1016/j.clinph.2023.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 07/03/2023] [Indexed: 07/26/2023]
Abstract
OBJECTIVE Epileptic fast ripple oscillations (FR, 250-500 Hz) indicate epileptogenic tissue with high specificity. However, their low amplitude makes detection demanding against noise. Since thermal noise is reduced by low impedance electrodes (LoZ), we investigate here whether this noise reduction is relevant in the FR frequency range. METHODS We analyzed intracranial electrocorticography during neurosurgery of 10 patients where a low impedance electrode was compared to a standard electrode (HiZ) with equal surface area during stimulation of the somatosensory evoked potential, which evokes a robust response in the FR frequency range. To estimate the noise level, we computed the difference between sweep 2n and sweep 2n + 1 for all sweeps. RESULTS The power spectral density of the noise spectrum improved for the LoZ over all frequencies. In the FR range, the median noise level improved from HiZ (0.153 µV) to LoZ (0.089 µV). For evoked FR, the detection rate improved (91% for HiZ vs. 100% for LoZ). CONCLUSIONS Low impedance electrodes for intracranial EEG reduce noise in the FR frequency range and may thereby improve FR detection. SIGNIFICANCE Improving the measurement chain may enhance the diagnostic value of FR as biomarkers for epileptogenic tissue.
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Affiliation(s)
| | - Marian C Neidert
- Klinik für Neurochirurgie, Universitätsspital Zürich, Universität Zürich, Switzerland; Klinik für Neurochirurgie, Kantonsspital St. Gallen, Switzerland
| | - Johannes Sarnthein
- Klinik für Neurochirurgie, Universitätsspital Zürich, Universität Zürich, Switzerland; Klinisches Neurozentrum, Universitätsspital Zürich, Switzerland.
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Song Z, Lee PJ, Hampton T. Acoustic environments of intensive care units during the COVID-19 pandemic. Appl Acoust 2022; 199:109037. [PMID: 36158734 PMCID: PMC9482849 DOI: 10.1016/j.apacoust.2022.109037] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 09/06/2022] [Accepted: 09/13/2022] [Indexed: 06/16/2023]
Abstract
This study aims to investigate the typical noise levels and noise sources in an intensive care unit (ICU) during the COVID-19 pandemic. Acoustic experiments were conducted over 24 hrs in patient wards and at nurse stations in four Chinese hospitals. From the measurements, noise levels and sources were analysed in terms of the A-weighted equivalent sound pressure levels (L Aeq) and A-weighted maximum Fast time-weighted sound pressure levels (L AFmax) over three different time periods during the day (i.e. day, evening and night). Overall, noise levels (L Aeq) for 24 hrs in all hospitals exceeded the World Health Organisation's (WHO) guide levels, varying from 51.1 to 60.3 dBA. The highest maximum noise level reached 104.2 dBA. The single-bedded wards (side rooms) were quieter than multi-bedded wards, and night time noise levels were quieter than daytime and evening across all hospitals. It was observed that the most dominant noise sources were talking/voices, door-closing, footsteps, and general activities (e.g. noise from cleaning equipment and cutlery sound). Footsteps became an unexpected dominant noise source during the pandemic because of the staff's disposable shoe covers which made footsteps noisier. Patient alarms and coughing varied significantly between patients. Talking/voices produced the highest maximum median values of the sound exposure level (SEL) and the maximum noise level at all sites. Noise levels in all the patient rooms were more than the WHO guidelines. The pandemic control guidelines had little impact on the noise levels in the ICUs.
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Affiliation(s)
- Ziwei Song
- Acoustics Research Unit, School of Architecture, University of Liverpool, Liverpool, United Kingdom
| | - Pyoung-Jik Lee
- Acoustics Research Unit, School of Architecture, University of Liverpool, Liverpool, United Kingdom
| | - Thomas Hampton
- ENT Department, Alder Hey Children's NHS Foundation Trust, Liverpool, United Kingdom
- Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
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Barrero JP, García-Herrero S, Mariscal MA. Influence of noise level and seniority in the workplace on the SAL, ELI and percentage of hearing loss indices in the diagnosis and prevention of hearing loss in the working population. J Safety Res 2022; 80:428-440. [PMID: 35249624 DOI: 10.1016/j.jsr.2021.12.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/18/2021] [Accepted: 12/20/2021] [Indexed: 06/14/2023]
Abstract
INTRODUCTION This research relates the most important work-related factors affecting the development of hearing loss to the main methods used as medical assessment criteria in the diagnosis of occupational deafness. These criteria are the Speech Average Loss Index (SAL), the Early Loss Index (ELI) and the Percentage of Hearing Loss, and are applied to data obtained from audiograms performed on workers in occupational medical examinations. METHOD Depending on the assessment method selected, these often return different results in grading an individual's hearing status and predicting how it will evolve. To address this problem, medical examinations (including audiograms) were carried out on a heterogeneous sample of 1,418 workers in Spain, from which demographic or personal data (gender, age, etc.), occupational data (noise level to which each individual is exposed, etc.) and other non-work-related factors (exposure to noise outside work, family history, etc.) were also gathered. Using Bayesian Networks, the conditional probability of an individual developing hearing loss was obtained taking into account all these factors and, specifically, noise level and length of service in the workplace. Sensitivity analyses were also carried out using the three scales (SAL, ELI and Percentage Hearing Loss Index), proving their suitability as tools the diagnosis and prediction of deafness. These networks were validated under the Receiver Operating Characteristic curve (ROC) criterion and in particular by the Area Under the Curve (AUC). RESULTS The results show that all three methods are deficient in so far as detecting preventive hearing problems related to noise in most workplaces. CONCLUSIONS The most restrictive methods for detecting possible cases of deafness are the SAL index and the Percentage Loss Index. The ELI index is the least restrictive of the three methods, but it is not able to discriminate the causes of hearing problems in an individual caused by exposure to noise, either by its intensity level or by the time of exposure to noise. Practical Applications: The use of the three methods in the field of occupational risk prevention is extremely limited and it seems reasonable to think that there is a need for the construction of new scales to correct or improve the existing ones.
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Affiliation(s)
- Jesús P Barrero
- University of Burgos, Faculty of Economic Sciences and Business Studies, Pza. de la Infanta Dª. Elena, s/n, 09001 Burgos, Spain
| | - Susana García-Herrero
- University of Burgos, Higher Polytechnic School, Avda. Cantabria s/n, 09006 Burgos, Spain
| | - Miguel A Mariscal
- University of Burgos, Higher Polytechnic School, Avda. Cantabria s/n, 09006 Burgos, Spain.
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Lecis M, Bardin S, Ciobanu CI, Ciobanu L. PEAKIT: A Gaussian Process regression analysis tool for chemical exchange saturation transfer spectra. J Magn Reson 2022; 334:107122. [PMID: 34906779 DOI: 10.1016/j.jmr.2021.107122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 11/26/2021] [Accepted: 11/30/2021] [Indexed: 06/14/2023]
Abstract
Chemical Exchange Saturation Transfer (CEST) is a powerful technique for metabolic imaging, capable of exploring concentrations in the μM to mM range. However, extracting quantitative information from Z-spectra can be challenging due to the non-CEST contributions present and the limited knowledge about the exchanging pools. The PEAKIT tool is proposed as an alternative approach to quantifying CEST peaks, which requires no prior assumptions about the frequency offset or the underlying shape of the baseline. Specifically, the tool takes as input an experimental Z-spectrum and proceeds to identify peak candidates. After a baseline estimation based on Gaussian Process regression, PEAKIT outputs the chemical shift offsets, the areas, the heights and the statistical significance of the detected peaks. The performance and limitations of the PEAKIT tool are discussed for in vitro and in vivo applications.
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Affiliation(s)
- Michele Lecis
- NeuroSpin, CEA, Gif-sur-Yvette, Paris-Saclay University, Saclay, France; Technical University of Munich, Munich, Germany
| | - Solène Bardin
- NeuroSpin, CEA, Gif-sur-Yvette, Paris-Saclay University, Saclay, France
| | | | - Luisa Ciobanu
- NeuroSpin, CEA, Gif-sur-Yvette, Paris-Saclay University, Saclay, France.
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Moore J, Searles S, Holterman LA, Simone C, Huggett K. Universal Design for TBL ®: Promoting Inclusion and Access for All Learners. Med Sci Educ 2020; 30:595-596. [PMID: 34457708 PMCID: PMC8368480 DOI: 10.1007/s40670-019-00827-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Our institution introduced team-based learning (TBL®) in 2015. Students shared concerns that the interactivity and loud volume of TBL might disadvantage students uncomfortable with group work, with auditory processing disorders, or who need testing accommodations. We share our efforts to ensure all students can benefit from TBL.
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Affiliation(s)
- Jesse Moore
- The Robert Larner MD College of Medicine, University of Vermont, 89 Beaumont Ave, Burlington, VT 05405 USA
| | - Sienna Searles
- The Robert Larner MD College of Medicine, University of Vermont, 89 Beaumont Ave, Burlington, VT 05405 USA
| | - Leigh Ann Holterman
- The Robert Larner MD College of Medicine, University of Vermont, 89 Beaumont Ave, Burlington, VT 05405 USA
| | - Cara Simone
- The Robert Larner MD College of Medicine, University of Vermont, 89 Beaumont Ave, Burlington, VT 05405 USA
| | - Kathryn Huggett
- The Robert Larner MD College of Medicine, University of Vermont, 89 Beaumont Ave, Burlington, VT 05405 USA
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Liu Y, Goudreau S, Oiamo T, Rainham D, Hatzopoulou M, Chen H, Davies H, Tremblay M, Johnson J, Bockstael A, Leroux T, Smargiassi A. Comparison of land use regression and random forests models on estimating noise levels in five Canadian cities. Environ Pollut 2020; 256:113367. [PMID: 31662255 DOI: 10.1016/j.envpol.2019.113367] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 10/07/2019] [Accepted: 10/08/2019] [Indexed: 05/22/2023]
Abstract
Chronic exposure to environment noise is associated with sleep disturbance and cardiovascular diseases. Assessment of population exposed to environmental noise is limited by a lack of routine noise sampling and is critical for controlling exposure and mitigating adverse health effects. Land use regression (LUR) model is newly applied in estimating environmental exposures to noise. Machine-learning approaches offer opportunities to improve the noise estimations from LUR model. In this study, we employed random forests (RF) model to estimate environmental noise levels in five Canadian cities and compared noise estimations between RF and LUR models. A total of 729 measurements and 33 built environment-related variables were used to estimate spatial variation in environmental noise at the global (multi-city) and local (individual city) scales. Leave one out cross-validation suggested that noise estimates derived from the RF global model explained a greater proportion of variation (R2: RF = 0.58, LUR = 0.47) with lower root mean squared errors (RF = 4.44 dB(A), LUR = 4.99 dB(A)). The cross-validation also indicated the RF models had better general performance than the LUR models at the city scale. By applying the global models to estimate noise levels at the postal code level, we found noise levels were higher in Montreal and Longueuil than in other major Canadian cities.
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Affiliation(s)
- Ying Liu
- Canadian Urban Environmental Health Research Consortium, Canada; Department of Environmental and Occupational Health, School of Public Health, University of Montreal, Montreal, QC H3C 3J7, Canada
| | - Sophie Goudreau
- Canadian Urban Environmental Health Research Consortium, Canada; Montreal Regional Department of Public Health, Montreal, QC H2L 1M3, Canada
| | - Tor Oiamo
- Canadian Urban Environmental Health Research Consortium, Canada; Department of Geography and Environmental Studies, Ryerson University, Toronto, ON M5B 2K3, Canada
| | - Daniel Rainham
- Canadian Urban Environmental Health Research Consortium, Canada; Department of Earth and Environmental Sciences, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Marianne Hatzopoulou
- Canadian Urban Environmental Health Research Consortium, Canada; Department of Civil Engineering, University of Toronto, Toronto, ON M5S 1A4, Canada
| | - Hong Chen
- Canadian Urban Environmental Health Research Consortium, Canada; Population Studies Division, Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada; Public Health Ontario, Toronto, ON M5G 1V2, Canada; Institute for Clinical Evaluative Sciences, Toronto, ON M4N 3M5, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, ON M5T 3M7, Canada
| | - Hugh Davies
- Canadian Urban Environmental Health Research Consortium, Canada; School of Population and Public Health, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Mathieu Tremblay
- Department of Public Health of Montérégie, Longueuil, QC J4K 2M3, Canada
| | - James Johnson
- Canadian Urban Environmental Health Research Consortium, Canada; Public Health Ontario, Toronto, ON M5G 1V2, Canada
| | - Annelies Bockstael
- School of Speech-Language Pathology and Audiology, University of Montreal, QC H3N 1X7, Canada
| | - Tony Leroux
- National Institute of Public Health of Quebec, Montreal, QC H2P 1E2, Canada
| | - Audrey Smargiassi
- Canadian Urban Environmental Health Research Consortium, Canada; Department of Environmental and Occupational Health, School of Public Health, University of Montreal, Montreal, QC H3C 3J7, Canada; National Institute of Public Health of Quebec, Montreal, QC H2P 1E2, Canada.
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Goswami M, Singh D, Vashist B, Marwaha S. Noise levels and sound pollution associated with various operative procedures and equipments in a pediatric dental environment-A clinical study. J Oral Biol Craniofac Res 2017; 7:182-187. [PMID: 29123997 PMCID: PMC5670304 DOI: 10.1016/j.jobcr.2017.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 06/30/2017] [Indexed: 11/21/2022] Open
Abstract
AIM To analyse sound levels and sound pollution in a Pediatric Dental Clinic and to analyse whether the levels are significant to the extent of being a health hazard. METHODS Noise levels were measured in a Pediatric dental clinic in an institutional setting with a precision noise level meter ((HTC 1350). Recordings were taken at different times of the day, at the centre, chair-side, reception, play area and four corners of the department keeping the microphone at a distance of 6 in. from the operator's ear. The noise levels of various equipments i.e. suction, micromotor, airotor were measured with the equipments turned on and during cutting operations with the microphone placed at a distance of 6 in. from the sound source. The sound levels for the laboratory equipments were taken at a distance of 6 in. and 2 m. RESULTS The highest mean sound levels were recorded at the reception, play area and chair-side area with least mean sound levels recorded at 9:00am which increased at 11:30am & 2:00pm and reduced again at 3:30pm The maximum sounds were produced by the lathe trimmer, airotor and scaler. CONCLUSION Noise levels in a pediatric clinic approach the level of risk of hearing loss [85 db(A)]. This would have a serious effect on both providers and patients and a concerted effort would be required to control the noise levels and thus avoid the potential health hazards that it poses.
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Affiliation(s)
- Mousumi Goswami
- Department of Pedodontics and Preventive Dentistry, ITS Dental College, Hospital and Research Centre 47, Knowledge Park III, Greater Noida, Uttar Pradesh 201308, India
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Zhang Y, Meng W, Fan B, Tang W. Biomimetic optimization research on wind noise reduction of an asymmetric cross-section bar. Springerplus 2016; 5:1221. [PMID: 27536505 PMCID: PMC4969254 DOI: 10.1186/s40064-016-2857-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 07/18/2016] [Indexed: 11/10/2022]
Abstract
BACKGROUND In this paper, we used the principle of biomimetics to design two-dimensional and three-dimensional bar sections, and used computational fluid dynamics software to numerically simulate and analyse the aerodynamic noise, to reduce drag and noise. METHODS We used the principle of biomimetics to design the cross-section of a bar. An owl wing shape was used for the initial design of the section geometry; then the feathered form of an owl wing, the v-shaped micro-grooves of a shark's skin, the tubercles of a humpback whale's flipper, and the stripy surface of a scallop's shell were used to inspire surface features, added to the initial section and three-dimensional shape. RESULTS Through computational aeroacoustic simulations, we obtained the aerodynamic characteristics and the noise levels of the models. These biomimetic models dramatically decreased noise levels.
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Affiliation(s)
- Yingchao Zhang
- State Key Laboratory of Automotive Simulation and Control, Jilin University, Changchun, 130022 China ; Key Laboratory Bionic Engineering, Ministry of Education, Jilin University, Changchun, 130022 China
| | - Weijiang Meng
- State Key Laboratory of Automotive Simulation and Control, Jilin University, Changchun, 130022 China
| | - Bing Fan
- State Key Laboratory of Automotive Simulation and Control, Jilin University, Changchun, 130022 China
| | - Wenhui Tang
- State Key Laboratory of Automotive Simulation and Control, Jilin University, Changchun, 130022 China
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Yamashita T, Miki A, Tabuchi A, Funada H, Kondo M. A novel method to reduce noise in electroretinography using skin electrodes: a study of noise level, inter-session variability, and reproducibility. Int Ophthalmol 2016; 37:317-324. [PMID: 27278187 PMCID: PMC5346432 DOI: 10.1007/s10792-016-0240-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 04/20/2016] [Indexed: 11/27/2022]
Abstract
To determine the feasibility of recording reproducible electroretinograms (ERGs) with skin electrodes using a new ERG system. Seventeen healthy volunteers were studied. The dark-adapted, bright-flash ERGs were recorded with a new ERG recording system (LE-4000, Tomey, Nagoya, Japan) in which the stimulus alternated between the eyes every 15 s, and each eye was stimulated eight times. The active skin electrode was placed on the lower eyelids of both eyes. The voltage changes of the non-stimulated eye were subtracted from that of the stimulated eye to try to increase the signal-to-noise ratio for eight stimulus cycles. The noise levels were measured from 12 subjects with and without the subtraction steps. ERGs were also recorded on five different days from five subjects, and the coefficient of variation (CV) and the intra-class correlation coefficients (ICCs) were calculated. The noise level without the subtraction step was 18.4 ± 8.4 μV, and it was significantly reduced to 13.8 ± 4.0 μV with the subtraction step (P = 0.001). Reproducible ERGs were obtained from each subject, and the average CV for the five subjects was 6.1 % for the a-wave amplitude, 7.7 % for the b-wave amplitude, and 7.7 % for the sum of the oscillatory potential (OP) amplitude. The ICC was 0.76 for the a-wave amplitude, 0.68 for the b-wave amplitude, and 0.72 for the sum of the OPs amplitude. These findings indicate that our new ERG recording methods shows noise reduction and good reproducibility with low inter-session variability even with skin electrodes.
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Affiliation(s)
- Tsutomu Yamashita
- Department of Sensory Science, Faculty of Health Science and Technology, Kawasaki University of Medical Welfare, 288 Matsushima, Kurashiki, 701-0193, Japan. .,Department of Ophthalmology, Kawasaki Medical School, Kurashiki, Japan.
| | - Atsushi Miki
- Department of Sensory Science, Faculty of Health Science and Technology, Kawasaki University of Medical Welfare, 288 Matsushima, Kurashiki, 701-0193, Japan.,Department of Ophthalmology, Kawasaki Medical School, Kurashiki, Japan
| | - Akio Tabuchi
- Department of Sensory Science, Faculty of Health Science and Technology, Kawasaki University of Medical Welfare, 288 Matsushima, Kurashiki, 701-0193, Japan
| | | | - Mineo Kondo
- Department of Ophthalmology, Mie University Graduate School of Medicine, Tsu, Japan
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Malakootian M, Ahmadian M, Yaghmaeian K, Dowlatshahi S, Ravandi MRG. Level changes of traffic noise in kerman city, southeast iran. Iran J Public Health 2012; 41:107-13. [PMID: 23113129 PMCID: PMC3481656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Accepted: 11/26/2011] [Indexed: 11/13/2022]
Abstract
BACKGROUND The purpose of this research was to determine the traffic noise level and changes in the Kerman City, southeast Iran in recent years. METHODS This cross-sectional study was carried out in 2008 to investigate the existing noise situation in Kerman. Sound levels (L(Max), L(Min), L(eq), L(99), L(90), L(50) and L(10)) were determined throughout 13 stations using sound level measurement system (model, CEL-440). Number of passing vehicles was also assessed at the sampled stations. RESULTS Sound level in all sampled stations was higher than Iran and World Health Organization guidelines. Comparison of L(eq) in different hours using statistical tests showed significant difference between different hours with 95 % confidence coefficient (P=0.01). Comparison of L(eq) throughout the week also showed that there was a significant difference (P=0.001) between Friday and workday. The comparison of L(eq) with the number of passing vehicles using Pearson correlation statistical test showed significant difference between the number of heavy vehicles passed and the level of L(eq) (P=0.001). It also showed that number of heavy vehicles caused the most noise levels. CONCLUSION The results of this study compared to a similar study conducted in 1999 showed an increasingly high noise level. Noise level increased from 1999 to 2008 by 3.89 % which is indicative of an increase in noise emission sources.
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Affiliation(s)
- M Malakootian
- Environmental Health Research Center and Dept. of Environmental Health Engineering, School of Public Health, Kerman University of Medical Sciences, Kerman, Iran
| | - M Ahmadian
- Social Development & Health Promotion Research Center, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - K Yaghmaeian
- Dept. of Environmental Health Engineering, Tehran University of Medical Sciences, Tehran, Iran,Corresponding Author: E-mail address:
| | - Sh Dowlatshahi
- Environmental Health Research Center and Dept. of Environmental Health Engineering, School of Public Health, Kerman University of Medical Sciences, Kerman, Iran
| | - MR Ghotbi Ravandi
- Dept. of Occupational Health, Kerman University of Medical Sciences, Kerman, Iran
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Frances RJ. Low noise level unmasks late potentials on signal-averaged electrocardiography. Exp Clin Cardiol 2010; 15:e61-e64. [PMID: 20959882 PMCID: PMC2954031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Accepted: 07/16/2010] [Indexed: 05/30/2023]
Abstract
INTRODUCTION Identification of late potentials requires the reduction of random noise by signal averaging. The importance of using a very low noise level (NL) as the end point of the averaging process in patients with ventricular tachycardia, the variation of results when a lower than standard NL was used and the modification of the sensitivity of the test when a very low NL was reached were evaluated. METHODS AND RESULTS Signal-averaged electrocardiograms were recorded in 36 patients with ischemic heart disease and spontaneous or induced sustained or nonsustained ventricular tachycardia. Thirteen patients showed negative or indeterminate results on recordings with an NL of 0.3 μV. Eight patients (group 1) underwent a second recording with an NL of 0.1 μV. Eight normal volunteers constituted the control group (group 2). The total duration of the filtered QRS vector magnitude (QRSd), the root mean square voltage of the terminal 40 ms of the vector magnitude (RMS(40)) and the low amplitude signal duration under 40 μV in the terminal portion of the vector magnitude (LAS) modifications were evaluated. A significant difference (P<0.01) in these parameters was observed in group 1 (15.88%, 48.25% and 68.5%, respectively) when both recordings were compared. Tests were positive in all patients (100%) with NL reduction. In group 2, tests were negative in all patients (100%) at both NLs (0.3 μV and 0.1 μV). QRSd was 1.18% longer, RMS(40) was 1.38% lower and LAS was 3.55% longer with NL reduction. CONCLUSION Late potentials in patients with ischemic heart disease, ventricular tachycardia, and a negative or indeterminate signal-averaged electrocardiogram may be detected if the NL is reduced to 0.1 μV. Reduction of the NL increased the sensitivity of the test without modifying its specificity.
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Affiliation(s)
- Raul J Frances
- Correspondence: Dr Raul J Frances, 4251 Salzedo Street, E-301, Miami, Florida 33146, USA. Telephone 305-799-7540, e-mail
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