scholarly journals Experimental investigation of the low-frequency impact sound transfer function of lightweight wooden floors via heel drops

Acta Acustica ◽  
2020 ◽  
Vol 4 (6) ◽  
pp. 23
Author(s):  
Yi Qin ◽  
Jin Jack Tan ◽  
Maarten Hornikx
Keyword(s):  
Natural Frequencies ◽  
Impact Force ◽  
Signal To Noise Ratio ◽  
Force Plate ◽  
Low Frequency ◽  
Superior Performance ◽  
High Input ◽  
Low Frequencies ◽  
Transfer Measurement ◽  
The Impact

The lightweight floor is a popular construction choice in buildings despite its poor low-frequency impact sound performance. This is exacerbated by common human activities, such as walking and jumping, that have high input force levels at low frequencies. Therefore, experimental evaluations of the low-frequency impact sound performance of a wooden lightweight floor are of interest to designers and researchers. The aim of this paper is to explore the use of heel drop for impact sound transfer measurement. An impact force plate has been built to accurately measure the heel-drop forces up to 200 Hz and the performances on two types of floors are evaluated. The heel drop has a higher energy level at low frequencies, resulting in higher coherence and signal-to-noise ratio and hence superior performance in characterizing the floors in the frequency range of below 40 Hz when compared to the impact hammer. Interestingly, in the case of a heel-drop excitation, the first natural frequencies of the floor decrease. It is in contrast to when a human is simply standing on it, which resulted in an increase of the natural frequencies upon impact hammer excitation.

scholarly journals Including measures of high gamma power can improve the decoding of natural speech from EEG

2019 ◽  
Author(s):  
Shyanthony R. Synigal ◽  
Emily S. Teoh ◽  
Edmund C. Lalor
Keyword(s):  
Brain Imaging ◽  
Neural Activity ◽  
Speech Processing ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Natural Speech ◽  
Low Frequencies ◽  
High Gamma ◽  
Gamma Power ◽  
Speech Tracking

ABSTRACTThe human auditory system is adept at extracting information from speech in both single-speaker and multi-speaker situations. This involves neural processing at the rapid temporal scales seen in natural speech. Non-invasive brain imaging (electro-/magnetoencephalography [EEG/MEG]) signatures of such processing have shown that the phase of neural activity below 16 Hz tracks the dynamics of speech, whereas invasive brain imaging (electrocorticography [ECoG]) has shown that such rapid processing is even more strongly reflected in the power of neural activity at high frequencies (around 70-150 Hz; known as high gamma). The aim of this study was to determine if high gamma power in scalp recorded EEG carries useful stimulus-related information, despite its reputation for having a poor signal to noise ratio. Furthermore, we aimed to assess whether any such information might be complementary to that reflected in well-established low frequency EEG indices of speech processing. We used linear regression to investigate speech envelope and attention decoding in EEG at low frequencies, in high gamma power, and in both signals combined. While low frequency speech tracking was evident for almost all subjects as expected, high gamma power also showed robust speech tracking in a minority of subjects. This same pattern was true for attention decoding using a separate group of subjects who undertook a cocktail party attention experiment. For the subjects who showed speech tracking in high gamma power, the spatiotemporal characteristics of that high gamma tracking differed from that of low-frequency EEG. Furthermore, combining the two neural measures led to improved measures of speech tracking for several subjects. Overall, this indicates that high gamma power EEG can carry useful information regarding speech processing and attentional selection in some subjects and combining it with low frequency EEG can improve the mapping between natural speech and the resulting neural responses.

scholarly journals Deep learning for low-frequency extrapolation from multioffset seismic data

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. R989-R1001 ◽  
Author(s):  
Oleg Ovcharenko ◽  
Vladimir Kazei ◽  
Mahesh Kalita ◽  
Daniel Peter ◽  
Tariq Alkhalifah
Keyword(s):  
Deep Learning ◽  
Seismic Data ◽  
Signal To Noise Ratio ◽  
Waveform Inversion ◽  
Low Frequency ◽  
Low Frequencies ◽  
Seismic Surveys ◽  
Full Waveform ◽  
Frequency Components ◽  
Marine Seismic

Low-frequency seismic data are crucial for convergence of full-waveform inversion (FWI) to reliable subsurface properties. However, it is challenging to acquire field data with an appropriate signal-to-noise ratio in the low-frequency part of the spectrum. We have extrapolated low-frequency data from the respective higher frequency components of the seismic wavefield by using deep learning. Through wavenumber analysis, we find that extrapolation per shot gather has broader applicability than per-trace extrapolation. We numerically simulate marine seismic surveys for random subsurface models and train a deep convolutional neural network to derive a mapping between high and low frequencies. The trained network is then tested on sections from the BP and SEAM Phase I benchmark models. Our results indicate that we are able to recover 0.25 Hz data from the 2 to 4.5 Hz frequencies. We also determine that the extrapolated data are accurate enough for FWI application.

scholarly journals Low-frequency sound affects active micromechanics in the human inner ear

2014 ◽  
Vol 1 (2) ◽  
pp. 140166 ◽  
Author(s):  
Kathrin Kugler ◽  
Lutz Wiegrebe ◽  
Benedikt Grothe ◽  
Manfred Kössl ◽  
Robert Gürkov ◽  
...  
Keyword(s):  
Inner Ear ◽  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Low Frequency ◽  
Short Exposure ◽  
Low Frequencies ◽  
Spontaneous Otoacoustic Emissions ◽  
Human Cochlea ◽  
Human Hearing ◽  
The Impact

Noise-induced hearing loss is one of the most common auditory pathologies, resulting from overstimulation of the human cochlea, an exquisitely sensitive micromechanical device. At very low frequencies (less than 250 Hz), however, the sensitivity of human hearing, and therefore the perceived loudness is poor. The perceived loudness is mediated by the inner hair cells of the cochlea which are driven very inadequately at low frequencies. To assess the impact of low-frequency (LF) sound, we exploited a by-product of the active amplification of sound outer hair cells (OHCs) perform, so-called spontaneous otoacoustic emissions. These are faint sounds produced by the inner ear that can be used to detect changes of cochlear physiology. We show that a short exposure to perceptually unobtrusive, LF sounds significantly affects OHCs: a 90 s, 80 dB(A) LF sound induced slow, concordant and positively correlated frequency and level oscillations of spontaneous otoacoustic emissions that lasted for about 2 min after LF sound offset. LF sounds, contrary to their unobtrusive perception, strongly stimulate the human cochlea and affect amplification processes in the most sensitive and important frequency range of human hearing.

scholarly journals Design and analysis of demolition robot arm based on finite element method

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401985396 ◽  
Author(s):  
Jiong Li ◽  
Yu Wang ◽  
Kai Zhang ◽  
Zhiqiao Wang ◽  
Jiaxing Lu
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Impact Force ◽  
Second Order ◽  
Robot Arm ◽  
Element Analysis ◽  
Front End ◽  
The Finite Element Analysis ◽  
The Impact ◽  
Ansys Workbench

As a novel robot which mainly engages in the demolition and transformation of various concrete buildings, the demolition robot has developed rapidly in recent years. The impact force is mainly produced by the breaking hammer installed in the front end of the arm. As the most important part of a demolition robot, the boom arm is mainly composed of four parts including a supporting arm, a main arm, a fore arm, and a breaking hammer system. In this article, a mechanical model of the boom arm is established, and the finite element analysis obtaining the first four-order natural frequencies and modes is carried out in ANSYS Workbench. The results reveal that the resonation can be easily stimulated when a hydraulic breaking hammer is at the second-order frequency. The mounting block of the hydraulic breaking hammer, the hinge parts of the supporting arm, and the main arm are easily deformed or damaged in the Y direction by analyzing the deformation in three directions of the second-order mode. After the structure optimization, the vibration characteristics of the two parts are significantly enhanced, which provides a theoretical basis for optimizing the prototype and gives a reference in the experimental modes.

On the Vibration of Rotor With Rotor/Stopper Rubbing

1999 ◽  
Author(s):  
Xingjian Dai ◽  
Xiaozhang Zhang ◽  
Zhaoxiong Jin
Keyword(s):  
Impact Force ◽  
Low Frequency ◽  
Experimental Methods ◽  
Harmonic Excitation ◽  
Rotor Vibration ◽  
Rotating Speed ◽  
Subharmonic Response ◽  
The Impact ◽  
Bearing System ◽  
Flywheel Rotor

Abstract The vibration of a flywheel rotor with rotor/stopper rubbing is investigated by experimental methods. In the experiments, the large amplitude of the rotor vibration is excited by the electromagnetic harmonic excitation force and thus causes the rubbing between the rotor and the stopper. The stable rubbing rotor vibration shows that the stopper can limit the amplitude of low frequency precession effectively. The rotor to stopper collision and rub appears occasionally. The rubbing has little effect on the rotating speed of the rotor. The forced vibration becomes complex and nonlinear in the time and frequency domain when the collision and rubbing occurs. The observed high order harmonics are sub-synchronous but not subharmonic response. The second modal forward whirl of the rotor-bearing system is excited by the impact force and decays quickly.

EFFECT OF THE FLUID ON THE IMPACT FORCE OF THE WET MISSILE

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Duc-Kien Thai ◽  
Seung-Eock Kim
Keyword(s):  
Impact Force ◽  
Force Plate ◽  
Time History ◽  
Research Centre ◽  
Element Analysis ◽  
Time Histories ◽  
Target Wall ◽  
Force Time ◽  
Missile Test ◽  
The Impact

In this paper, the force-time histories of soft missiles, with and without filled water, impacting the target wall were investigated using finite element analysis. The force plate tests, with a dry missile (test FP8) and a wet missile (test FP16) carried out by Technical Research Centre of Finland (VTT), were used. The numerical analysis results were verified by comparing with those of experiments. A parametric analysis with different missile velocities was also performed to investigate the force-time history and impulse of the missile impact on target plate. Based on a comparison with the Riera approach, the coefficients were proposed to modify the Riera function. The analysis results show that, the Riera function accurately predicted the impact force time history in the case of the dry missile. However, in the case of the wet missile, the coefficients α from 1.24 to 1.45 are recommended to be added to the second term of the Riera function in the case in which the impact velocity is in the range of 70 m/s to 200 m/s.

Interpretation of full-azimuth broadband land data from Saudi Arabia and implications for improved inversion, reservoir characterization, and exploration

2013 ◽  
Vol 1 (2) ◽  
pp. T167-T176 ◽  
Author(s):  
Brian P. Wallick ◽  
Luis Giroldi
Keyword(s):  
Saudi Arabia ◽  
Seismic Data ◽  
Acoustic Impedance ◽  
Reservoir Characterization ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Gas Field ◽  
Frequency Model ◽  
Low Frequencies ◽  
Limited Bandwidth

Interpretation of conventional land seismic data over a Permian-age gas field in Eastern Saudi Arabia has proven difficult over time due to low signal-to-noise ratio and limited bandwidth in the seismic volume. In an effort to improve the signal and broaden the bandwidth, newly acquired seismic data over this field have employed point receiver technology, dense wavefield sampling, a full azimuth geometry, and a specially designed sweep with useful frequencies as low as three hertz. The resulting data display enhanced reflection continuity and improved resolution. With the extension of low frequencies and improved interpretability, acoustic impedance inversion results are more robust and allow greater flexibility in reservoir characterization and prediction. In addition, because inversion to acoustic impedance is no longer completely tied to a wells-only low-frequency model, there are positive implications for exploration.

Low Frequency NQR using Double Contact Cross-relaxation

2000 ◽  
Vol 55 (1-2) ◽  
pp. 37-40
Author(s):  
David Stephenson ◽  
John A. S. Smith
Keyword(s):  
Ammonium Sulphate ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Cross Relaxation ◽  
Relaxation Technique ◽  
Signal To Noise ◽  
Low Frequencies ◽  
Line Shapes ◽  
Ammonium Dichromate ◽  
Noise Ratio

A cross-relaxation technique is described which involves two spin contacts per double reso-nance cycle. The result is an improvement in signal to noise ratio particularly at low frequencies. Experimental spectra and analyses are presented: 14N in ammonium sulphate showing that the tech-nique gives essentially the same information as previous studies; 14N in ammonium dichromate determining e2Qq/h as (76±3) kHz and η = 0.84±.04; 7Li in lithium acetylacetonate for which the spectrum (corrected for Zeeman distortion) yields e2Qq/h = (152 ±5) kHz and η=.5 ±.2. Calculated spectra are presented to demonstrate the η dependence of the line shapes for 7Li.

Probe Reversal and Pressure Based Bias Error Correction Procedures Applied to Intensity Measurements in Planar Standing Waves

1995 ◽  
Vol 117 (1) ◽  
pp. 56-61
Author(s):  
R. W. Guy ◽  
H. Luchian
Keyword(s):  
Standing Wave ◽  
Standing Waves ◽  
Low Frequency ◽  
Superior Performance ◽  
Bias Error ◽  
Low Frequencies ◽  
Pressure Correction ◽  
Phase Errors ◽  
Intensity Measurements ◽  
Probe Spacing

An analytical application of probe reversal and pressure correction strategies to minimize channel phase errors in P-P intensity measurements within discrete frequency standing waves is made. Two potential error sources, error of position upon reversal and error of pressure correction, are examined and found negligible at low frequencies but likely to be problematic at high frequencies. It is predicted that pressure correction or probe reversal can lead to superior performance when compared with measures without correction at modest and higher standing wave ratios in true intensity assessment; the frequency range for a given probe spacing is also extended. The correction procedures are then applied to low frequency measurements (63 Hz and 125 Hz) for a range of standing wave ratios. It is found that correction procedures generally lead to better results than uncorrected measures, but beyond a standing wave ratio of about 30 dB at 63 Hz additional error source arises which renders inaccurate the result of correction procedures, particularly for smaller probe spacing measures.

scholarly journals The Impact of the Treatment Method of Root Crops on Micro flora during their Storage

2019 ◽  
Vol 9 (1) ◽  
pp. 4273-4278
Keyword(s):  
Magnetic Induction ◽  
Treatment Time ◽  
Low Frequency ◽  
Treatment Method ◽  
Integrated Treatment ◽  
Low Frequencies ◽  
Anaerobic Microorganisms ◽  
Root Crops ◽  
Different Temperatures ◽  
The Impact

The study aims at determining the effect of the treatment method of root crops before storage, as well as storage parameters, on the dynamics of their microflora, namely, the quantity of bacterial microflora, mesophilic aerobic and optionally anaerobic microorganisms (MAaOAM), as well as molds. When storing garden carrot at t = +(2±1) °C (during 56 days), the amount of bacterial microflora of the samples subjected to integrated treatment decreased by 2.5 times by the end of storage; the number of mold fungi decreased twice compared to the control. When storing garden carrot at t = +(25±1) °C (for 21 days) the amount of bacterial microflora in the samples treated by electromagnetic fields of extremely low frequencies (with the following parameters: frequency – 28 Hz, the treatment time – 5 min, the magnetic induction – 12 mTl), and by Vitaplan biologic preparation (at the concentration of 106 CFU/g, and in the amount of 2.5 ml/kg), decreased by 2.1 times, while the number of mold fungi reduced by 1.5 times. When storing garden beet at t = +(2±1) °C for 56 days, the amount of bacterial microflora of samples, subjected to integrated treatment for 5 min at a frequency of 15, 24, and 30 Hz, and magnetic induction of 9 mTl, as well as treatment with Bactofit biological preparation (at the concentration of 106 CFU/g in amount of 2.5 ml/kg), decreased by 1.5 times compared to the control, while the number of mold fungi decreased by 2.3 times. When storing garden beet at t = +(25±1) °C (for 21 days), the quantity of bacterial microflora of samples, subjected to integrated treatment, was by 2.8 times lower compared to the control, while the number of mold fungi reduced by 1.8 times. It has been revealed that the integrated treatment of root crops with biopreparations and extremely low frequency (ELF) electric and magnetic fields (EMF) more effectively inhibits the development of pathogenic microflora compared to treatment only with biopreparations or treatment only by ELF-EMF. Significant retardation of growth rates was revealed in both bacterial and fungal pathogenic microflora during storage of root crops at different temperatures.

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