Acoustic Noise Level Research Articles

Work-Related Communicative Profile of Voice Teachers: Effects of Classroom Noise on Voice and Hearing Abilities

Vocal instructors during their normal workday are exposed to high noise levels that can affect their voice and hearing health. The goal of this study was to evaluate the voice and hearing status of voice instructors before and after lessons and relate these evaluations with voice and noise dosimetry taken during lessons. Eight voice instructors volunteered to participate in the study. The protocol included (1) questionnaires, (2) pre/post assessment of voice quality and hearing status, and (3) voice and noise dosimetry during lessons. Acoustic measurements were taken of the unoccupied classrooms. In six of eight classrooms, the measured noise level was higher than the safety recommendations set by National Institute for Occupational Safety and Health. The background noise level and the reverberation time in the classrooms were in compliance with the national standard recommendations. We did not find a clear pattern comparing pre- and post-measurements of voice quality consistent among genders. In all subjects, the Sound Pressure Levels mean increased, and the standard deviation of fundamental frequency decreased indicating association to vocal fatigue. Previous studies link these changes to increasing vocal fatigue. The audiometric results revealed seven out of eight instructors have sensorineural hearing loss. The interaction of the acoustic space and noise levels can contribute to the development of hearing and voice disorders for voice instructors. If supported by larger sample size, the results of this pilot study could justify the need for a hearing and voice conservation program for music faculty.

Silent T1 mapping using the variable flip angle method with B1 correction.

To compare the silent rotating ultrafast imaging sequence (RUFIS) to a traditional Cartesian spoiled gradient-echo (SPGR) acquisition scheme for variable flip angle (VFA) mapping. A two-point VFA measurement was performed using RUFIS and Cartesian SPGR in a quantitative phantom and healthy volunteers. To correct for errors, a novel silent magnetization prepared map acquisition (SIMBA) was developed, which combined with RUFIS VFA allows for a completely silent mapping protocol. The silent protocol was found to have comparable repeatability but higher reproducibility in vivo compared to the standard SPGR protocol, and showed no increase in acoustic noise levels above background noise levels compared to a 33 dBA increase for the SPGR acquisition. VFA mapping using RUFIS is a feasible alternative to SPGR, achieving silent mapping with comparable acquisition time.

A power-efficient audio acquisition system for smart city applications

Acoustic noise has adverse effects on human activities. Aside from hearing impairment and stress-related illnesses, it can also interfere with spoken communication, reduce human performance and affect the quality of life. As urbanization is intensifying, the potential benefits of reducing noise pollution in smart-city environments are extensive. Noise levels can be collected and analyzed using a wireless sensor network which can monitor the noise level by using microphones. However, every wireless system struggles in terms of the battery requirements needed for continuous data collection and monitoring. In this paper, the design of a testbed for a smart microphone system is presented. To save power, a microcontroller and an Analog-to-Digital Converter (ADC) dynamically switch between high and low power modes in response to environmental noise. Specifically, the high powered components are triggered by a spike in the acoustic noise level. Three wireless technologies, WiFi (2.4 GHz), Bluetooth Low Energy (BLE) 4.0 and Zigbee were examined. According to the results, the power consumption of a node can be lowered by 97% when idle based on the testbed.

Near-silent distortionless DWI using magnetization-prepared RUFIS.

To develop a near-silent and distortionless DWI (sd-DWI) sequence using magnetization-prepared rotating ultrafast imaging sequence. A rotating ultrafast imaging sequence was modified with driven-equilibrium diffusion preparation, including eddy-current compensation methods. To compensate for the T1 recovery during readout, a phase-cycling method was used. Both compensation methods were validated in phantoms. The optimized sequence was compared with an EPI diffusion sequence for image distortion, contrast, ADC, and acoustic noise level in phantoms. The sequence was evaluated in 1 brain volunteer, 5 prostate volunteers, and 10 pediatric patients with joint diseases. Combination of several eddy-current compensation methods reduced the artifact to an acceptable level. Phase cycling reduced T1 recovery contamination during readout. In phantom scans, the optimized sequence generated similar image contrast to the EPI diffusion sequence, and ADC maps between the sequences were comparable; sd-DWI had significantly lower acoustic noise (P < .05). In vivo brain scan showed reduced image distortion in sd-DWI compared with the EPI diffusion, although residual motion artifact remains due to brain pulsation. The prostate scans showed that sd-DWI can provide similar ADC compared with EPI diffusion, with no image distortion. Patient scans showed that the sequence can clearly depict joint lesions. An sd-DWI sequence was developed and optimized. Compared with conventional EPI diffusion, sd-DWI provided similar diffusion contrast, accurate ADC measurement, improved image quality, and minimal ambient scanning noise. The sequence showed the ability to obtain in vivo diffusion contrast in relatively motion-free body regions, such as prostate and joint.

Joint Audio-Ultrasound Food Recognition for Noisy Environments.

Continuous recognition of ingested foods without user intervention is very useful for the pre-screening of obesity and diet-related disease. An automatic food recognition method that combines the two modalities of audio and ultrasonic signals (US) is proposed in this study. Under a noise-free environment, classification accuracy of an audio-only recognizer is generally higher than that of US-only recognizers, but the performance of US recognizers is unaffected by acoustic noise levels. In the recognition system presented herein, the likelihood score of the audio-US feature was given by a linear combination of class-conditional observation log-likelihoods for two classifiers, using the appropriate weights. We developed a weighting process adaptive to signal-to-noise ratios (SNRs). The main objective here involves determining the optimal SNR classification boundaries and constructing a set of optimum stream weights for each SNR class. A feasibility test was conducted to verify the usefulness of the proposed method by conducting recognition experiments on seven types of food. The performance was compared with conventional methods that use in-ear and throat microphones. The proposed method yielded remarkable levels of recognition performance of 90.13% for artificially added noise and 89.67% under actual noisy environments, when the SNR ranged from 0 to 20 dB.

Magnetostrictive Properties of the Grain-Oriented Silicon Steel Sheet under DC-Biased and Multisinusoidal Magnetizations

As an intrinsic property, elasticity of soft material is affected significantly by the externally applied alternating magnetic field. Magnetostrictive properties of the grain-oriented (GO) silicon steel under DC-biased and multisinusoidal magnetizations are measured by using a laser-based measuring system. Magnetostriction curves of the GO silicon steel sheet under different magnetizations are obtained and the influence of frequency and DC bias on the magnetostrictive property is observed and analyzed based on the measured data. In addition, the spectrum of magnetostriction under harmonic magnetization is obtained, and the acoustic noise level of the GO silicon steel sheet represented by the A-weighted decibel value caused by magnetostriction is measured under DC-biased and multisinusoidal magnetizations. The measurement results are applied to the simulation of the three-limb laminated core model, and the effects of DC bias and harmonics on magnetic flux density and displacement are analyzed.

Analysis of the Acoustically Noise Situation in an Urbanized Area in the Presence of Vehicular and Industrial Noise

Acoustic noise is now becoming one of the important problems of the technosphere. The source of such noise in the streets of large cities is mainly motor transport, as well as industrial enterprises located in the city and construction sites. In the report some results of monitoring of acoustic pollution of the big industrially developed cities (on the example of the city of Murom) are considered. Monitoring is carried out with the help of a combined ecology-meteorological system. The measurement errors due to the standard octave analysis procedure with a control at central weighted frequencies are analyzed. It is shown that the application of the full spectral analysis using the fast Fourier transform allows us to compensate for these errors. The features of the construction of the measuring channel used in the monitoring procedure are considered. Some results of analysis of the spectrum and levels of acoustic noise on the streets of the city at different periods of the day are given. It is shown that in the most heavily loaded areas of the city, combining the activity of traffic flows and the functioning of industrial enterprises, the maximum values of sound pressure level of acoustic noise can reach 100 dB. Both maximum and average values of sound pressure are analyzed from the point of view of their compliance with the current sanitary norms. The conclusion is made that the actual noise levels exceed the maximum permissible levels for open spaces.

Пригнічення акустичних перешкод у системах дистанційного моніторингу атмосфери з використанням ґратчастих фільтрів

The questions related to the choice of effective frequency of sounding signal in the acoustic sounding systems of the ground layers of atmosphere in the district of airport are investigated and presented. For an achievement of big heights it is necessary that the sounding signal frequency does not exceed 1 kHz. However in this range the noise level from airliners is high in an airport. To provide flight safety in an airport it is impotent to know the wind parameters on small heights, therefore researches are fulfiled for sounding signal frequencies of 3 kHz and 5 kHz. The parameter evaluation accuracy of the sounding acoustic signal reflected from an atmosphere inhomogeneity is defined by the statistical simulation technique with the adaptive suppression process of the airliners interference. The conducted experiments show that for these sounding signals frequencies the estimation accuracy of the reflected signal frequency depends negligibly on the chosen frequency. So, the sounding signal frequency may be changed in a wide range during sounding system operation near-by an airport, with taking into account descriptions of interference spectrums. Experiments were conducted for the acoustic interference created by the airliners Boeing 707 and Boeing 737. It is shown also, that application of the adaptive lattice filters and adaptive filters with the finite impulse response (FIR) for suppression of the acoustic interference created by airliners in airports substantially brings down the interference influence on the estimation accuracy of a wind speed measured by acoustic sounding systems. At weak acoustic interference and noise level application of the adaptive lattice filters and filters with FIR gives approximately identical results, and at considerable noise levels the use of the latticed filters is more preferable. The research results comport with conclusions on the practical application of adaptive lattice filters and linear prediction filters with FIR.

Speech enhancement using ultrasonic doppler sonar

The quality of speech reproduced using conventional single-channel speech enhancement schemes is seriously affected by acoustic noise level. Nonacoustic sensors have the ability to reveal certain speech attributes that are lost in noisy acoustic signals. This study validated the use of ultrasonic doppler frequency shifts caused by facial movements for enhancing audio speech contaminated by high levels of acoustic noise. A 40 kHz ultrasonic beam is incident to a speaker’s face. The received signals were first demodulated and converted to a spectral feature parameter. The spectral feature derived from the ultrasonic Doppler signal (UDS) was concatenated with spectral features from noisy speech, which were then used to estimate the magnitude of the spectrum of clean speech. A nonlinear regression approach was employed in this estimation where the relationship between audio-UDS features and the corresponding clean speech is represented by deep neural networks (DNN). The feasibility of the proposed enhancement method was tested on a 1 h audio-UDS corpus and four different types of noise data. The results showed that, both objectively and subjectively, the best performance was obtained when the audio and UDS were used cooperatively. A correlation analysis was also carried out to investigate the usefulness of multi-directional ultrasonic sensing. The results showed that the performance was affected by the number of the adopted UDS channels, particularly in cases of low levels of SNRs.

Detection Small Aircraft by Acoustic Radiation

Introduction. The problem of detecting small aircraft (SA) gave impetus to the creation of devices and systems for detecting different principles of operation. The detection of drones is complicated by their low visibility, both in the electromagnetic and acoustic ranges of the wavelengths and the feature of the flight path. Flight altitude can vary from units to tens of meters, and the dynamics of movement, from lagging to acceleration in an arbitrary direction. The use of radar allows detect drones in open areas at a distance of up to 1000m. Acoustic observation methods provide detection in complex terrain and the presence of green spaces. The detection range depends on the selected receiver, the radiation level of the object and the level of acoustic noise in the observation area. The development of the algorithm for calculating the detection range for the given detection characteristics seems to be relevant. Theoretical results. For the detection of flying objects it is proposed to use a receiver that provides non-coherent processing of acoustic signals - typical detection channel. The algorithm for calculating the maximum range of detection of SA is based on the statistical theory of detecting a noise-like signal disguised by interference. The algorithm for calculating the maximum detection range of SA is based on the statistical theory of detection of a noise-like signal. The sequence of calculating the maximum range of detection of LLA is reduced to establishing the type, effective frequency band and level of the radiation signal, determining the level of interference in the reception area, calculating the CW detection parameter, calculating the maximum detection range. Conclusions. To detect SA by acoustic radiation, it is proposed to use a detector according to the scheme of a typical detection channel. An algorithm for calculating the probability of detecting a noise signal is presented and a decision rule is established. The paper proposes an algorithm for calculating the maximum distance for detection of SA. An important factor in assessing the range is the distribution of air temperature with altitude and the direction of movement of air masses. Therefore, the algorithm should be improved taking into account the meteorological situation.

Fine-Tooth Iron-Core Linear Synchronous Motor for Low Acoustic Noise Applications

The design of a novel low-noise high-force linear motor for precision positioning applications, such as in semiconductor lithography, is presented in this paper. New magnetic designs achieve low noise and vibration by reducing high spatial-frequency magnetic field components, which cause harmonic vibrations of a moving stage. To reduce such force harmonic content, our new motor has fine teeth, narrow slots with high slot aspect ratio, five phases, and a moving skewed Halbach magnet array. As compared with a commercially available iron-core motor, in our new design, the acoustic noise level in Pascals is reduced by more than 90%, corresponding to a 20 dB reduction in sound pressure level, even with a nonskewed magnet array. Using a skewed magnet array, the cogging-driven and velocity-dependent noise is further reduced by 90% in Pascals. This new linear motor simultaneously is capable of very high shear force densities in order to support high-acceleration motions, and thus provides new options for high-performance and quiet linear motion devices.

Analysis of Influence of Coil Gradient System on Vibration Properties and Acoustic Noise Level Generated by the Low Field MRI Device

Abstract The paper focuses on investigation of influence of the volume inserted in the scanning area of the magnetic resonance imaging (MRI) device working with a low magnetic field generated by a pair of permanent magnets on vibration and acoustic noise. In addition, its aim is to evaluate the influence of different types of used scan sequences, different settings of slice orientation and scan parameters on the energy and spectral properties of vibration and noise generated by the gradient coil system of the MRI device. Two basic measurements were performed within this work: mapping of sound pressure levels in the MRI device vicinity and parallel acquisition of vibration signals by sensors mounted on the lower and upper parts of the MRI gradient system. The paper next analyzes changes in properties of the vibration signals for the examined person lying in the scanning area compared with the situation of using only the testing phantom. Spectral characteristics of the recorded vibration signals are then analyzed statistically, and compared visually and numerically. The obtained results of the detailed analysis will be used for improvement of noise suppression algorithms applied to a speech signal recorded simultaneously with scanning of the human vocal tract for its 3D modeling.

Assessment of quiet T2 weighted PROPELLER sequence in pediatric abdominal imaging

IntroductionElevated acoustic noise during Magnetic Resonance Imaging (MRI) has been associated with patient anxiety and altered cochlear function. Acoustic Reduction Technique (ART) T2 weighted (T2w) periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) has been studied in brain MR but not abdominopelvic imaging. The purpose of our study was to evaluate the image quality and acoustic noise level of ART T2w PROPELLER sequence in comparison with the conventional T2w PROPELLER sequence in pediatric abdomino-pelvic imaging. MethodsEleven consecutive pediatric patients undergoing abdomino-pelvic MRI were scanned on a 3 Tesla magnet using standard and ART T2w PROPELLER sequences. After scanning completion, objective sound level measurements were performed with a sound level meter and microphone. Mann-Whitney U test was used for a non-parametric two-tailed statistical analysis of acoustics, image rating and scan time with significance level set to 0.05. Overall inter-rater agreement was calculated using Cohen's kappa coefficient. ResultsEleven pediatric patients (4 females and 7 males) between 26 days and 18 years of age (mean = 10.0, SD = 5.8) were included. ART T2w produced lower levels of acoustic noise than standard technique in a comparison of mean decibel readings from eleven trials of standard and ART T2w (p value = 0.00008). Streak artifacts were rated greater in ART T2w by both raters (p-value = 0.00278 and 0.00252). There was no significant difference in bile duct blurring, respiratory ghosting, pulsation, fat suppression or hepatic parenchymal depiction. ConclusionPresence of additional streaking artifacts should be considered along with the benefit of reduced acoustic noise from ART T2w.

In vivo MRI with Concurrent Excitation and Acquisition using Automated Active Analog Cancellation

Magnetic resonance imaging (MRI) provides excellent cross-sectional images of the soft tissues in patients. Unfortunately, MRI is intrinsically slow, it exposes patients to severe acoustic noise levels, and is limited in the visualization of certain tissues such as bone. These limitations are partly caused by the timing structure of the MRI exam which first generates the MR signal by a strong radio-frequency excitation and later acquires the weak MRI signal. Concurrent excitation and acquisition (CEA) can overcome these limitations, but is extremely challenging due to the huge intensity difference between transmit and receive signal (up to 100 dB). To suppress the strong transmit signals during signal reception, a fully automated analog cancellation unit was designed. On a 3 Tesla clinical MRI system we achieved an on-resonance analog isolation of 90 dB between the transmit and receive path, so that CEA images of the head and the extremities could be acquired with an acquisition efficiency of higher than 90% at sound pressure levels close to background noise. CEA with analog cancellation might provide new opportunities for MRI in tissues with very short T2 relaxation times, and it offers a silent and time-efficient MRI acquisition.

UNISeC: Inspection, Separation, and Classification of Underwater Acoustic Noise Point Sources

Advancements in oceanic research have resulted in a plethora of activities such as undersea oil/gas exploration, environmental monitoring, sonar-based coastal surveillance, which have each increased the acoustic noise levels in the ocean and have raised concerns in the scientific community about the effect of human-generated sounds on marine life. Knowledge of the statistical characteristics of noise sources and their spatial distribution is paramount for understanding the impact on marine life as well as for regulating and policing such activities. Furthermore, studies have shown that assuming the underwater noise probability density function to be Gaussian, exponential, or Weibull is often not valid; therefore, statistically profiling the sources of the ambient noise is also essential to improve the performance of acoustic communication systems in the harsh underwater environment. In this paper, a novel solution based on the blind source separation method is proposed to enable separation of underwater acoustic noise point sources in the presence of channel propagation multipath. The proposed Underwater Noise Inspection, Separation, and Classification (UNISeC) system performs several pre- and postprocessing steps forming a novel gray-box model. Assuming there is no prior information on the noise sources, UNISeC estimates the number of such sources as well as characterizes and classifies them via a recursive pilot-aided probing method while minimizing the environmental acoustic contamination. A correlation-based characterization as well as power spectral density based classification approaches are investigated to verify the proposed method. Several scenarios are also presented and evaluated in detail via simulations.

High-speed switched reluctance machine: natural frequency calculation and acoustic noise prediction

In this study, an analytical model is proposed for natural frequency calculation and acoustic noise prediction for high speed switched reluctance machines. The developed natural frequency model results are compared with the mechanical finite element analysis results in terms of 6 different mode shapes that cause the majority of the acoustic noise in switched reluctance machines. The results show that the analytical results are consistent with the numerical method results with minimum 90% matching. Based on the natural frequency calculation model, a new acoustic noise prediction method is developed that only needs a radial force waveform as an input emerging on stator pole surfaces. The comparison of the developed and the numerical results clearly indicates that the acoustic noise level of the switched reluctance machine can be effectively found during the design process without using time-consuming numerical methods.

Management of acoustic risks for buildings near airports

Global population growth leads to a rapid urbanization of big cities and the development of transport infrastructure (airports, railway and bus stations). The strong urbanization in the cities of developing countries leads to a gradual rapprochement of dwellings and companies of airport zones. A fact that is real in Mali, where Bamako airport area has become an inhabited urban zone for some years by a part of the population. Given the importance of Bamako's airport traffic (West African crossroads), the proximity of the dwelling houses must receive the authorities and scientist's attention on the occupants' safety and quality life. The noise levels generated all around the airport zone throughout landings and take-offs by different aircraft types require an assessment of the acoustic noise level, the level of noise exposure and the building acoustic performance near the airport for users comfort and quality of life.In this article, we give in one hand the general notions on the inhabitants discomfort indicators, the building acoustics and, on the other hand, non-quality identification, and the discomfort factors whose resolution contributes to improving the building acoustic and environmental performance. These assessment studies are based on acoustic measurements and in-situ surveys from construction actors and users. Data from these surveys are processed with an evaluation methodology developed to improve knowledge and strategies aimed at preventing or minimizing the acoustic risks near airports. The capitalization of knowledge resulting from this study can serve as experience feedback through good practices advocacy and corrective and preventive solutions for building construction and renovation projects.

Audio-visual word prominence detection from clean and noisy speech

In this paper we investigate the audio-visual processing of linguistic prosody, more precisely the detection of word prominence, and examine how the additional visual information can be used to increase the robustness when acoustic background noise is present. We evaluate the detection performance for each modality individually and perform experiments using feature and decision fusion. For the latter we also consider the adaptive fusion with fusion weights adjusted to the current acoustic noise level. Our experiments are based on a corpus with 11 English speakers which contains in addition to the speech signal also videos of the speakers’ heads. From the acoustic signal we extract features which are well known to capture word prominence like loudness, fundamental frequency and durational features. The analysis of the visual signal is based on features derived from the speaker’s rigid head movements and movements of the speaker’s mouth. We capture the rigid head movements by tracking the speaker’s nose. Via a two-dimensional Discrete Cosine Transform (DCT) calculated from the mouth region we represent the movements of the speaker’s mouth. The results show that the rigid head movements as well as movements inside the mouth region can be used to discriminate prominent from non-prominent words. The audio-only detection yields an Equal Error Rate (EER) averaged over all speakers of 13%. Based only on the visual features we obtain 20% of EER. When we combine the visual and the acoustic features we only see a small improvement compared to the audio-only detection for clean speech. To simulate background noise we added 4 different noise types at varying SNR levels to the acoustic stream. The results indicate that word prominence detection is quite robust against additional background noise. Even at a severe Signal to Noise Ratio (SNR) of −10 dB the EER only rises to 35%. Despite this the audio-visual fusion leads to notable improvements for the detection from noisy speech. We observe relative reductions of the EER of up to 79%.

Reduced acoustic noise in diffusion tensor imaging on a compact MRI system.

To investigate the feasibility of substantially reducing acoustic noise while performing diffusion tensor imaging (DTI) on a compact 3T (C3T) MRI scanner equipped with a 42-cm inner-diameter asymmetric gradient. A-weighted acoustic measurements were made using 10 mT/m-amplitude sinusoidal waveforms, corresponding to echo-planar imaging (EPI) echo spacing of 0.25 to 5.0 ms, on a conventional, whole-body 3T MRI and on the C3T. Acoustic measurements of DTI with trapezoidal EPI waveforms were then made at peak gradient performance on the C3T (80 mT/m amplitude, 700 T/m/s slew rate) and at derated performance (33 mT/m, 10 to 50 T/m/s) for acoustic noise reduction. DTI was acquired in two different phantoms and in seven human subjects, with and without gradient-derating corresponding to multi- and single-shot acquisitions, respectively. Sinusoidal waveforms on the C3T were quieter by 8.5 to 15.6 A-weighted decibels (dBA) on average as compared to the whole-body MRI. The derated multishot DTI acquisition noise level was only 8.7 dBA (at 13 T/m/s slew rate) above ambient, and was quieter than non-derated, single-shot DTI by 22.3 dBA; however, the scan time was almost quadrupled. Although derating resulted in negligible diffusivity differences in the phantoms, small biases in diffusivity measurements were observed in human subjects (apparent diffusion coefficient = +9.3 ± 8.8%, fractional anisotropy = +3.2 ± 11.2%, radial diffusivity = +9.4 ± 16.8%, parallel diffusivity = +10.3 ± 8.4%). The feasibility of achieving reduced acoustic noise levels with whole-brain DTI on the C3T MRI was demonstrated. Magn Reson Med 79:2902-2911, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Reduction of Power Transformer Core Noise Generation Due to Magnetostriction-Induced Deformations Using Fully Coupled Finite-Element Modeling Optimization Procedures

This paper focuses on the development of an algorithm for the prediction of transformer core deformation, using a fully coupled magneto-mechanical approach. An imposed magnetic flux method coupled with finite-element modeling is employed for the magnetic resolution. The constitutive law of the material is considered with a simplified multi-scale model describing both magnetic and magnetostrictive anisotropies. Magnetostriction is introduced as an input free strain of a mechanical problem to get the deformation and displacement fields. A 3-D estimation of acoustic power is carried out to evaluate the global core deformation and acoustic noise level. The numerical process is applied to a three-phase transformer made of grain-oriented FeSi core, leading to a set of noise estimation for different flux excitations and core geometries.