Frequency spectrum analysis of plant storage tissue during deterioration

1977 ◽  
Vol 55 (18) ◽  
pp. 2437-2438 ◽  
Author(s):  
Terry A. Tattar ◽  
David M. Sylvia
Keyword(s):  
Low Frequency ◽  
Soft Rot ◽  
Healthy Plant ◽  
Storage Tissue ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Pass Filter ◽  
Pass Through ◽  
High Pass ◽  
Plant Storage

Frequency spectra of healthy plant storage tissue indicate that the tissue acts as a high-pass filter that attenuates low frequencies and allows high frequencies to pass through. During progressive deterioration of the tissue from infection of soft-rot bacteria, the frequency spectra indicated a loss in ability of the tissues to filter low frequency signals.

Pulse-shape distortion introduced by broadband deconvolution

1992 ◽  
Vol 82 (1) ◽  
pp. 238-258
Author(s):  
Stuart A. Sipkin ◽  
Arthur L. Lerner-Lam
Keyword(s):  
Transfer Function ◽  
Ground Motion ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequencies ◽  
Pass Filter ◽  
Long Period ◽  
High Pass Filter ◽  
Low Pass ◽  
High Pass

Abstract The availability of broadband digitally recorded seismic data has led to an increasing number of studies using data from which the instrument transfer function has been deconvolved. In most studies, it is assumed that raw ground motion is the quantity that remains after deconvolution. After deconvolving the instrument transfer function, however, seismograms are usually high-pass filtered to remove low-frequency noise caused by very long-period signals outside the frequency band of interest or instabilities in the instrument response at low frequencies. In some cases, data must also be low-pass filtered to remove high-frequency noise from various sources. Both of these operations are usually performed using either zero-phase (acausal) or minimum-phase (causal) filters. Use of these filters can lead to either bias or increased uncertainty in the results, especially when taking integral measures of the displacement pulse. We present a deconvolution method, based on Backus-Gilbert inverse theory, that regularizes the time-domain deconvolution problem and thus mitigates any low-frequency instabilities. We apply a roughening constraint that minimizes the long-period components of the deconvolved signal along with the misfit to the data, emphasizing the higher frequencies at the expense of low frequencies. Thus, the operator acts like a high-pass filter but is controlled by a trade-off parameter that depends on the ratio of the model variance to the residual variance, rather than an ad hoc selection of a filter corner frequency. The resulting deconvolved signal retains a higher fidelity to the original ground motion than that obtained using a postprocess high-pass filter and eliminates much of the bias introduced by such a filter. A smoothing operator can also be introduced that effectively applies a low-pass filter. This smoothing is useful in the presence of blue noise, or if inferences about source complexity are to be made from the roughness of the deconvolved signal.

Preamplifier With Ultra Low Frequency Cutoff for Infrasonic Condenser Microphone

2012 ◽  
Author(s):  
Rasmus Trock Kinnerup ◽  
Arnold Knott ◽  
Ole Cornelius Thomsen ◽  
Kresten Marbjerg ◽  
Per Rasmussen
Keyword(s):  
Input Impedance ◽  
Dynamic Range ◽  
Cutoff Frequency ◽  
Low Frequency ◽  
Input Resistance ◽  
Bias Current ◽  
Microphone Signal ◽  
Low Frequencies ◽  
Pass Filter ◽  
Condenser Microphone

Measuring infrasonic sound sets high requirements on the instruments used. Typically the measurement chain consists of a microphone and a preamplifier. As the input resistance of the preamplifier forms a high pass filter with the capacitance of the microphone in the picofarad range, measuring ultra low frequencies becomes a challenge. The electric preamplifier presented in this paper together with a prepolarized condenser microphone form a measurement system. The developed preamplifier connects the microphone signal directly to the input of an operational amplifier with ultra high input impedance. The bias current for the preamplifier further complicates the signal amplification. A configuration of two diode-connected FETs provide the input bias current. The resulting input impedance of nearly 1 TΩ yields a total lower limiting −3 dB cutoff frequency of 8 mHz and a dynamic range of 95 dB. Being able to measure down to ultra low frequencies in the infrasonic frequency range will aid actors in the debate on wind turbine noise. Sonic booms from supersonic flights include frequencies down to 10 mHz and the preamplifier proposed in this paper will aid scientists trying to modify the N-shaped shock wave at high level which prohibits flights in land zones.

scholarly journals A sciaenid swim bladder with long skinny fingers produces sound with an unusual frequency spectrum

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hin-Kiu Mok ◽  
Shih-Chia Wu ◽  
Soranuth Sirisuary ◽  
Michael L. Fine
Keyword(s):  
Frequency Spectrum ◽  
Fundamental Frequency ◽  
Pulse Repetition Rate ◽  
Sound Production ◽  
Swim Bladder ◽  
Low Frequencies ◽  
Pass Filter ◽  
Number Of Cycles ◽  
Almost All ◽  
High Pass

Abstract Swim bladders in sciaenid fishes function in hearing in some and sound production in almost all species. Sciaenid swim bladders vary from simple carrot-shaped to two-chambered to possessing various diverticula. Diverticula that terminate close to the ears improve hearing. Other unusual diverticula heading in a caudal direction have not been studied. The fresh-water Asian species Boesemania microlepis has an unusual swim bladder with a slightly restricted anterior region and 6 long-slender caudally-directed diverticula bilaterally. We hypothesized that these diverticula modify sound spectra. Evening advertisement calls consist of a series of multicycle tonal pulses, but the fundamental frequency and first several harmonics are missing or attenuated, and peak frequencies are high, varying between < 1–2 kHz. The fundamental frequency is reflected in the pulse repetition rate and in ripples on the frequency spectrum but not in the number of cycles within a pulse. We suggest that diverticula function as Helmholz absorbers turning the swim bladder into a high-pass filter responsible for the absence of low frequencies typically present in sciaenid calls. Further, we hypothesize that the multicycle pulses are driven by the stretched aponeuroses (flat tendons that connect the sonic muscles to the swim bladder) in this and other sciaenids.

scholarly journals Computer simulation of low‐frequency electromagnetic data acquisition

Geophysics ◽  
1983 ◽  
Vol 48 (9) ◽  
pp. 1219-1232 ◽  
Author(s):  
William A. San Filipo ◽  
Gerald W. Hohmann
Keyword(s):  
Computer Simulation ◽  
Data Acquisition ◽  
Dynamic Range ◽  
Low Frequency ◽  
Noise Removal ◽  
Digital Data ◽  
Low Frequencies ◽  
Pass Filter ◽  
Natural Field ◽  
Field Noise

Computer simulation of low‐frequency electromagnetic (EM) digital data acquisition in the presence of natural field noise demonstrates several important limitations and considerations. Without a remote reference noise removal scheme, it is difficult to obtain an adequate ratio of signal to noise below 0.1 Hz for frequency‐domain processing and below 0.3 Hz base frequency for time‐domain processing for a typical source‐receiver configuration. A digital high‐pass filter substantially facilitates rejection of natural field noise above these frequencies; however, at lower frequencies where much longer stacking times are required, it becomes ineffective. Use of a remote reference to subtract natural field noise extends these low‐frequency limits by one decade, but the remote reference technique is limited by the resolution and dynamic range of the instrumentation. Gathering data in short segments so that natural field drift can be offset for each segment allows a higher gain setting to minimize dynamic range problems. The analysis is also applicable to the induced polarization technique in which similar problems arise at low frequencies in the presence of telluric noise.

Generation of Low-Frequency Spiciness Variability in the Thermocline*

2011 ◽  
Vol 41 (2) ◽  
pp. 365-377 ◽  
Author(s):  
Thomas Kilpatrick ◽  
Niklas Schneider ◽  
Emanuele Di Lorenzo
Keyword(s):  
Markov Model ◽  
Large Scale ◽  
Spatial Scales ◽  
Low Frequency ◽  
Passive Tracer ◽  
Wind Stress Curl ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Geostrophic Advection

Abstract The generation of variance by anomalous advection of a passive tracer in the thermocline is investigated using the example of density-compensated temperature and salinity anomalies, or spiciness. A coupled Markov model is developed in which wind stress curl forces the large-scale baroclinic ocean pressure that in turn controls the anomalous geostrophic advection of spiciness. The “double integration” of white noise atmospheric forcing by this Markov model results in a frequency (ω) spectrum of large-scale spiciness proportional to ω−4, so that spiciness variability is concentrated at low frequencies. An eddy-permitting regional model hindcast of the northeast Pacific (1950–2007) confirms that time series of large-scale spiciness variability are exceptionally smooth, with frequency spectra ∝ ω−4 for frequencies greater than 0.2 cpy. At shorter spatial scales (wavelengths less than ∼500 km), the spiciness frequency spectrum is whitened by mesoscale eddies, but this eddy-forced variability can be filtered out by spatially averaging. Large-scale and long-term measurements are needed to observe the variance of spiciness or any other passive tracer subject to anomalous advection in the thermocline.

scholarly journals Viscoelastic nanoscale properties of cuticle contribute to the high-pass properties of spider vibration receptor ( Cupiennius salei Keys)

2007 ◽  
Vol 4 (17) ◽  
pp. 1135-1143 ◽  
Author(s):  
Michael E McConney ◽  
Clemens F Schaber ◽  
Michael D Julian ◽  
Friedrich G Barth ◽  
Vladimir V Tsukruk
Keyword(s):  
Low Frequency ◽  
Young Modulus ◽  
Surface Force ◽  
Mechanical Stimuli ◽  
Low Frequencies ◽  
Cupiennius Salei ◽  
Vibration Sensors ◽  
Force Curves ◽  
Epicuticular Layer ◽  
High Pass

Atomic force microscopy (AFM) and surface force spectroscopy were applied in live spiders to their joint pad material located distal of the metatarsal lyriform organs, which are highly sensitive vibration sensors. The surface topography of the material is sufficiently smooth to probe the local nanomechanical properties with nanometre elastic deflections. Nanoscale loads were applied in the proximad direction on the distal joint region simulating the natural stimulus situation. The force curves obtained indicate the presence of a soft, liquid-like epicuticular layer (20–40 nm thick) above the pad material, which has much higher stiffness. The Young modulus of the pad material is close to 15 MPa at low frequencies, but increases rapidly with increasing frequencies approximately above 30 Hz to approximately 70 MPa at 112 Hz. The adhesive forces drop sharply by about 40% in the same frequency range. The strong frequency dependence of the elastic modulus indicates the viscoelastic nature of the pad material, its glass transition temperature being close to room temperature (25±2 °C) and, therefore, to its maximized energy absorption from low-frequency mechanical stimuli. These viscoelastic properties of the cuticular pad are suggested to be at least partly responsible for the high-pass characteristics of the vibration sensor's physiological properties demonstrated earlier.

Recovery of Slow Potentials in AC-Coupled Electrocorticography: Application to Spreading Depolarizations in Rat and Human Cerebral Cortex

2009 ◽  
Vol 102 (4) ◽  
pp. 2563-2575 ◽  
Author(s):  
Jed A. Hartings ◽  
Tomas Watanabe ◽  
Jens P. Dreier ◽  
Sebastian Major ◽  
Leif Vendelbo ◽  
...  
Keyword(s):  
Aneurysmal Subarachnoid Hemorrhage ◽  
Low Frequency ◽  
Inverse Filter ◽  
Slow Potential ◽  
Pass Filter ◽  
Human Cortex ◽  
Morphologic Characteristics ◽  
Full Band ◽  
Particular Solution ◽  
High Pass

Cortical spreading depolarizations (spreading depressions and peri-infarct depolarizations) are a pathology intrinsic to acute brain injury, generating large negative extracellular slow potential changes (SPCs) that, lasting on the order of minutes, are studied with DC-coupled recordings in animals. The spreading SPCs of depolarization waves are observed in human cortex with AC-coupled electrocorticography (ECoG), although SPC morphology is distorted by the high-pass filter stage of the amplifiers. Here, we present a signal processing method to reverse these distortions and recover approximate full-band waveforms from AC-coupled recordings. We constructed digital filters that reproduced the phase and amplitude distortions introduced by specific AC-coupled amplifiers and, based on this characterization, derived digital inverse filters to remove these distortions from ECoG recordings. Performance of the inverse filter was validated by its ability to recover both simulated and real low-frequency input test signals. The inverse filter was then applied to AC-coupled ECoG recordings from five patients who underwent invasive monitoring after aneurysmal subarachnoid hemorrhage. For 117 SPCs, the inverse filter recovered full-band waveforms with morphologic characteristics typical of the negative DC shifts recorded in animals. Compared with those recorded in the rat cortex with the same analog and digital methods, the negative DC shifts of human depolarizations had significantly greater durations (1:47 vs. 0:45 min:sec) and peak-to-peak amplitudes (10.1 vs. 4.2 mV). The inverse filter thus permits the study of spreading depolarizations in humans, using the same assessment of full-band DC potentials as that in animals, and suggests a particular solution for recovery of biosignals recorded with frequency-limited amplifiers.

Application of EMD to Integrated Signal Trend Extraction

2012 ◽  
Vol 591-593 ◽  
pp. 2072-2076 ◽  
Author(s):  
Ye Qu Chen ◽  
Wen Zheng ◽  
Xie Ben Wei
Keyword(s):  
Empirical Mode Decomposition ◽  
Low Frequency ◽  
Data Driven ◽  
Pass Filter ◽  
Effective Implementation ◽  
Trend Extraction ◽  
Mode Decomposition ◽  
Calculation Results ◽  
High Pass ◽  
Emd Method

Huang’s data-driven technique of Empirical Mode Decomposition (EMD) is presented, and issues related to its effective implementation are discussed. Integrating signal directly will produce a trend, it will cause distortion and interfere with the calculation results. This paper discusses the reasons that cause the integrated signal trend, compares the different methods for extracting trend. The traditional steps use the linear fitting and a high-pass filter to remove low frequency signal to extract trend. This paper uses Empirical Mode Decomposition (EMD) method to extract integrated signals trend, discussed the advantages of Empirical Mode Decomposition (EMD) method in this case, proves that Empirical Mode Decomposition (EMD) has a good application in integrated signal trend extraction.

Construction of a High-Pass Digital Filter from a Low-Pass Digital Filter

1994 ◽  
Vol 10 (4) ◽  
pp. 374-381 ◽  
Author(s):  
Stephen D. Murphy ◽  
D. Gordon E. Robertson
Keyword(s):  
Digital Filter ◽  
Low Frequency ◽  
Frequency Noise ◽  
Band Pass Filter ◽  
Low Frequency Noise ◽  
Pass Filter ◽  
Low Pass Filter ◽  
High Pass Filter ◽  
Low Pass ◽  
High Pass

To remove low-frequency noise from data such as DC-bias from electromyo-grams (EMGs) or drift from force transducers, a high-pass filter was constructed from a low-pass filter of known characteristics. A summary of the necessary steps required to transform the low-pass digital were developed. Contaminated EMG and force platform data were used to test the filter. The high-pass filter successfully removed the low-frequency noise from the EMG signals. The high-pass filter was then cascaded with the low-pass filter to produce a band-pass filter to enable simultaneous high- and low-frequency noise reduction.

scholarly journals Spectra of Low-Frequency Ground Vibrations Generated by High-Speed Trains on Layered Ground

1997 ◽  
Vol 16 (4) ◽  
pp. 257-270 ◽  
Author(s):  
V.V. Krylov
Keyword(s):  
High Speed ◽  
Low Frequency ◽  
Ground Vibration ◽  
Ground Vibrations ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
High Speed Trains ◽  
Frequency Components ◽  
Noticeable Reduction ◽  
Layered Ground

Increase in speeds of modern railway trains is usually accompanied by higher levels of generated ground vibrations. In the author's earlier paper [V.V. Krylov, Applied Acoustics, 44, 149–164 (1995)], it has been shown that especially large increase in vibration level may occur if train speeds v exceed the velocity of Rayleigh surface waves in the ground cR., i.e., v > cR. Such a situation might arise, for example, with French TGV trains for which speeds over 515 km/h have been achieved. The present paper investigates the effect of geological layered structure of the ground on ground vibrations generated by high-speed trains. It is shown that, since Rayleigh wave velocities in layered ground are dispersive and normally increase at lower frequencies associated with deeper penetration of surface wave energy into the ground, the trans-Rayleigh condition v > cR may not hold at very low frequencies. This will cause a noticeable reduction in low-frequency components of generated ground vibration spectra. Theoretical results are illustrated by numerically calculated frequency spectra of ground vibrations generated by single axle loads travelling at different speeds and by TGV or Eurostar high-speed trains.

Sign in / Sign up

Export Citation Format

Share Document