Sensitive Frequency Range Research Articles

대형 풍력발전기 소음원 분석

Wind turbine noise become main environmental problem as wind energy have been installed all around. Noise from large wind turbine give annoyance to listener, moreover it increase loading to whole system by restricting blade tip speed. However accurate noise mechanism of wind turbine is not yet examined. This paper reviewed noise source and analysis theory. Broadband noise if main component of wind turbine noise and airfoil self noise is main noise source. These make acoustic analogy hard to apply for analysis. For this reason, experimental equation is method for wind turbine noise prediction up to now. Spectrum analysis shows that vortex shedding noise exists around Hz. This region is most sensitive frequency range to human. Thus it is necessary to reduce this noise source.

Sound generated by a payao and comparison with auditory sensitivity of jack mackerelTrachurus japonicus

Sound generated by a payao, an anchored bamboo fish aggregating device, is believed to be attractive to fish; but until now, there is no available record of payao-generated sound. This study presents payao-generated sound recorded by a hydrophone at water depths of 5, 10 and 15 m from a fixed distance of 3 m relative to the payao, and compares the sound with the auditory sensitivity of jack mackerel Trachurus japonicus measured at discrete frequencies from 100 to 2000 Hz using the auditory brainstem response protocol. A consistent peak appeared in the sound spectrum at 49 Hz and showed an increasing sound pressure level with depth, which suggests that payao sound may come from the anchor rope. However, the contribution of the bamboo raft can not yet be discounted. The hearing threshold curve indicated that the most sensitive frequency range in jack mackerel is from 92.1 dB at 800 Hz to 111.0 dB at 200 Hz. These results show that the dominant frequency range of payao sound does not correspond with the high sensitivity frequency range of fish hearing.

Optimal light beams and mirror shapes for future LIGO interferometers

We report the results of a recent search for the lowest value of thermal noise that can be achieved in LIGO by changing the shape of mirrors, while fixing the mirror radius and maintaining a low diffractional loss. The result of this minimization is a beam with thermal noise a factor of 2.32 (in power) lower than previously considered Mesa Beams and a factor of 5.45 (in power) lower than the Gaussian beams employed in the current baseline design. Mirrors that confine these beams have been found to be roughly conical in shape, with an average slope approximately equal to the mirror radius divided by arm length, and with mild corrections varying at the Fresnel scale. Such a mirror system, if built, would impact the sensitivity of LIGO, increasing the event rate of observing gravitational waves in the frequency range of maximum sensitivity roughly by a factor of 3 compared to an Advanced LIGO using Mesa beams (assuming all other noises remain unchanged). We discuss the resulting beam and mirror properties and study requirements on mirror tilt, displacement, and figure error, in order for this beam to be used in LIGO detectors.

Coevolution of auditory sensitivity and temporal resolution with acoustic signal space in three songbirds

Coevolution between senders and receivers is expected to produce a close match between signal design and sensory biology. We evaluated this hypothesis in songbirds by comparing aspects of acoustic signal space with the frequency range of auditory sensitivity and temporal resolution in tufted titmice, Baeolophus bicolor ; house sparrows, Passer domesticus ; and white-breasted nuthatches, Sitta carolinensis . Auditory measurements were made electrophysiologically from the scalp using two classes of auditory-evoked potentials: the auditory brain-stem response (ABR) and the envelope-following response (EFR). ABRs to tone-burst stimuli indicated maximum sensitivity from 2.2 to 3.2 kHz in all species, but 12–14 dB greater sensitivity in titmice than in sparrows and nuthatches at 6.4 kHz (the highest frequency tested). Modulation rate transfer functions based on EFRs to amplitude-modulated tones suggested greater temporal resolution in titmice and sparrows than in nuthatches. Conservation of the frequency range of maximum sensitivity across species resulted in a mismatch with the dominant frequency of song in sparrows. The mismatch may reflect auditory constraints coupled with selection for high-frequency song and relaxed selection for a close match between sender and receiver due to small territory size. Consistent with coevolution between senders and receivers, high-frequency sensitivity varied with the maximum frequency of species-specific vocalizations, whereas temporal resolution varied with the maximum rate of envelope periodicity. Enhanced high-frequency sensitivity of the titmouse may reflect a specialization for processing high-frequency communication signals such as alarm calls.

Integrated Controller Design for Automotive Semi-Active Suspension Considering Vehicle Behavior with Steering Input

This study aims at achieving simultaneous realization of ride comfort and steering stability in the controller design for semi-active suspension considering the most sensitive frequency range of human body and vehicle behavior at steering. In this study, a method which can improve both the ride comfort and the vehicle stability is proposed by separating the control range in terms of frequency domain, where the frequency weightings on the controlled variables are used. Furthermore, the controller is scheduled in time domain in order to realize the positive pitch angle mode at the slalom. In this study, the dynamics of road disturbance is supposed and is accommodated into that controller to make the control performance more effective. In order to investigate the effectiveness of the proposed control system, the computer simulations are carried out by using a full vehicle model which has variable stiffness and damping semi-active suspension system. As a result, it is demonstrated that the proposed method can realize improving the ride comfort, reducing the vehicle motion, and synchronizing the roll and pitch angles caused by steering.

The gravitational-wave spectrum of a non-axisymmetric torus around a rapidly spinning black hole

The gravitational-wave spectrum emitted by a non-axisymmetric torus rotating at an angular velocity ΩT, is derived in terms of a structure function representing a combination of sausage-tilt modes in the torus in the limit of an incompressible fluid. The analysis of the gravitational-wave spectrum is then applied to a model proposed recently, in which a highly magnetized torus interacts with a stellar mass, Kerr black hole via poloidal field lines that connect the torus and the horizon. The deformation of the torus results from global magnetic instabilities when the magnetic field strength inside the torus exceeds a few times 1015Gauss. The dynamics of the system is illustrated using a non-MHD toy model. It is found that, quite generally, most of the gravitational-wave energy emitted is in the frequency range of sensitivity of LIGO and Virgo.

Searching for gravitational waves from known pulsars

We present upper limits on the amplitude of gravitational waves from 28 isolated pulsars using data from the second science run of LIGO. The results are also expressed as a constraint on the pulsars' equatorial ellipticities. We discuss a new way of presenting such ellipticity upper limits that takes account of the uncertainties of the pulsar moment of inertia. We also extend our previous method to search for known pulsars in binary systems, of which there are about 80 in the sensitive frequency range of LIGO and GEO 600.

Search for gravitational waves associated with the gamma ray burst GRB030329 using the LIGO detectors

We have performed a search for bursts of gravitational waves associated with the very bright Gamma Ray Burst GRB030329, using the two detectors at the LIGO Hanford Observatory. Our search covered the most sensitive frequency range of the LIGO detectors (approximately 80-2048 Hz), and we specifically targeted signals shorter than 150 ms. Our search algorithm looks for excess correlated power between the two interferometers and thus makes minimal assumptions about the gravitational waveform. We observed no candidates with gravitational wave signal strength larger than a pre-determined threshold. We report frequency dependent upper limits on the strength of the gravitational waves associated with GRB030329. Near the most sensitive frequency region, around 250 Hz, our root-sum-square (RSS) gravitational wave strain sensitivity for optimally polarized bursts was better than h_RSS = 6E-21 Hz^{-1/2}. Our result is comparable to the best published results searching for association between gravitational waves and GRBs.

Prediction of density and mechanical properties of human trabecular bone in vitro by using ultrasound transmission and backscattering measurements at 0.2–6.7 MHz frequency range

The ultrasound (US) backscattering method has been introduced as an alternative for the through-transmission measurement of sound attenuation and speed in diagnosis of osteoporosis. Both attenuation and backscattering depend strongly on the US frequency. In this study, 20 human trabecular bone samples were measured in transmission and pulse-echo geometry in vitro. The aim of the study was to find the most sensitive frequency range for the quantitative ultrasound (QUS) analyses. Normalized broadband US attenuation (nBUA), speed of sound (SOS), broadband US backscatter (BUB) and integrated reflection coefficient (IRC) were determined for each sample. The samples were spatially scanned with five pairs of US transducers covering a frequency range of 0.2–6.7 MHz. Furthermore, mechanical properties and density of the same samples were determined. At all frequencies, SOS, BUB and IRC showed statistically significant linear correlations with the mechanical properties or density of human trabecular bone (0.51 < r < 0.82, 0.54 < r < 0.81 and 0.70 < r < 0.85, respectively). In contrast to SOS, IRC and BUB, nBUA showed statistically significant correlations with mechanical parameters or density at the centre frequency of 1 MHz only. Our results suggest that frequencies up to 5 MHz can be useful in QUS analyses for the prediction of bone mechanical properties and density. Since the use of higher frequencies provides better axial and spatial resolution, improved structural analyses may be possible. While extensive attenuation of high frequencies in trabecular bone limits the clinically feasible frequency range, selection of optimal frequency range for in vivo QUS application should be carefully considered.

Optimal Control of Active Ambulance Stretcher Suspension

A theoretical model of two-dimensional active control for ambulance stretcher suspension is proposed. The shaping filter equations of time domain are developed to provide optimal estimates of the disturbance dynamics. Numerical calculations are carried out to examine the effectiveness of proposed control scheme. It shows that the optimal control with disturbance feed-forwarded provides significant reduction of vertical and pitch vibration transmission compared with the passive stretcher suspension. The relative displacement and resonance peak values of vibration components in the sensitive frequency range of human body are effectively suppressed in comparison with that of the 1-DOF active control stretcher.

Comparison of computer codes for propagation of high-frequency energy from blast waves

Current environmental regulation requires that the Department of Defense assess the potential impact of noise from military training on endangered wildlife. One concern is the effect of noise from Army weapons on the hearing of bats. High frequencies are generated from nonlinear propagation of finite-amplitude shock waves created by explosions. These frequencies may be harmful to bats because their auditory systems are sensitive to high-frequency information that they use for flight navigation, communication, and hunting. Determining the spatial extent of high-frequency propagation requires an understanding of the short rise times associated with blast waves. A comparison of computer codes is performed for the most sensitive frequency range of bat hearing, 10–100 kHz. Earlier published results by the authors [A. Loubeau and V. W. Sparrow, Proc. NOISE-CON 2004, 193–201 (2004)] are compared to numerical solutions of the generalized Burgers equation with molecular relaxation included. The approaches considered are a time-domain method by Cleveland and a hybrid time–frequency-domain algorithm by Anderson. The results are also compared to recent experimental explosion data obtained by the US Army. [Work supported by US Army Engineer Research and Development Center CERL.]

Early Detection of Ototoxicity Using 1/6th-Octave Steps

The National Center for Rehabilitative Auditory Research has developed a protocol to provide early identification of ototoxicity for patients receiving ototoxic medications. The initial work involved patients with relatively good high-frequency hearing and resulted in the use of an individualized, sensitive frequency range separated by 1/6th-octave intervals. This protocol tested pure-tone frequencies at 1/6th-octave steps above 9 kHz, but only conventional audiometric frequencies were tested below 9 kHz. More recently, the testing protocol was expanded to include 1/6th-octave testing below 9 kHz. The primary question of interest was to determine whether adding 1/6th-octave test frequencies below 9 kHz would increase the ototoxicity detection rate for patients with poorer hearing. Results indicated 76 of the 210 (36.2%) ears that demonstrated initial ototoxic hearing change would have been missed or detected later if only conventional frequency testing was conducted.Therefore, for individuals with poorer hearing, expanding the use of the 1/6th-octave test protocol provides earlier identification of ototoxicity.

Effects of amplitude modulation on the coding of interaural time differences of low-frequency sounds in the inferior colliculus. I. Response properties.

Most sounds in the natural environment are amplitude-modulated (AM). To determine if AM alters the neuronal sensitivity to interaural time differences (ITDs) in low-frequency sounds, we tested neuronal responses to a binaural beat stimulus with and without modulation. We recorded from single units in the inferior colliculus of the unanesthetized rabbit. We primarily used low frequency ( approximately 25 Hz) modulation that was identical at both ears. We found that modulation could enhance, suppress, or not affect the discharge rate. In extreme cases, a neuron that showed no response to the unmodulated binaural beat did so when modulation was added to both ears. At the other extreme, a neuron that showed sensitivity to the unmodulated binaural beat ceased firing with modulation. Modulation could also affect the frequency range of ITD sensitivity, best ITD, and ITD tuning width. Despite these changes in individual neurons, averaging across all neurons, the peak and width of the population ITD function remained unchanged. Because ITD-sensitive neurons also time-locked to the modulation frequency, the location and sound attributes are processed simultaneously by these neurons.

Hearing in reindeer (Rangifer tarandus).

The audiogram of two yearling male reindeer (Rangifer tarandus tarandus) were determined using a conditioned suppression/avoidance procedure. During testing, the animal was drinking from a metal bowl while pure tone signals were played at random intervals and followed by an electric shock in the bowl. By breaking contact with the bowl at sound signals, the animal avoided the shock. The animals detected sounds at intensities of 60 dB or less from 70 Hz to 38 kHz. The frequency range of best sensitivity was relatively flat from 1 kHz to 16 kHz, with a best sensitivity of 3 dB at 8 kHz. The hearing ability of reindeer is similar to the hearing ability of other ungulates.

Frequency characteristics and intrinsic oscillations in a neuronal network

The phenomena of frequency sensitivity in weak signal detection and the 40 Hz oscillation in a neuronal network have been interpreted based on the intrinsic oscillations of the system. There exists a most sensitive frequency range of 20–60 Hz, over which the signal-to-noise ratio has a large value. This results from the resonance between the subthreshold intrinsic oscillation and the periodic signal. The network can exhibit the synchronous 40 Hz oscillation only with constant bias, which is due to the intrinsic features of neurons and long-range interactions between them.

Firing and signal transduction associated with an intrinsic oscillation in neuronal systems

We study the nonlinear firing and signal transduction of a neuron subject to both a constant stimulus and a weak periodic signal, each of which is too small to, separately, fire spikes for the neuron. The subthreshold constant stimulus, regarded as the total input to the neuron from other neurons and from the external world, is found to give rise to only an intrinsic subthreshold oscillation. This oscillation can lead to the transduction of the weak periodic signal via a mechanism similar to stochastic resonance. This may enable us to understand reported experimental results of oscillation associated signal transduction and of finite signal-to-noise ratio in the absence of external noise. In addition, the most sensitive frequency range for signal transduction is also found.

マコガレイの聴覚しきい値について

The auditory thresholds for 10 specimens of the marbled sole Pleuronectes yokohamae were determined by heartbeat conditioning using pure tone stimuli of 9 frequencies from 60 to 1, 000Hz, which were coupled with an electric shock. The marbled sole could hear sound in the frequency range from 60 to 1, 000Hz, and the lowest threshold was 92.5dB re 1μPa at 100Hz. Hearing ability declined rapidly with increasing frequency above 300Hz, but little difference occurred in hearing ability between 400 and 500Hz. The results show that the auditory thresholds of marbled sole are higher and its sensitive frequency range is narrower than that for fish that have swimbladder.

Low-temperature AC microcalorimetry: Possibilities and limitations

The possibilities and limitations of the low-temperature modulated calorimetry are investigated experimentally and theoretically. The effects of the sample holder and of the heat leakage into the thermocouple wires on the measured temperature oscillations are discussed. It is shown that the effects can lead to incorrect measurements and impose limitations on the calorimeter sensitivity and on the width of the appropriate frequency range of the sample temperature modulation. A proper choice of materials and external parameters enables the construction of the calorimeter with sensitivity of ca. 10 −8 J/K at 5 K. The presented calorimeter provides the possibility of the heat-capacity measurements up to 10 3 Hz at low temperatures. High sensitivity and wide frequency range are of principal importance for investigations of complex heat capacity.

The cochlea of Tadarida brasiliensis: specialized functional organization in a generalized bat

Tadarida brasiliensis mexicana employs a broad-band sonar system at frequencies between 80 and 20 kHz and is characterized by non-specialized hearing capabilities. The cochlear frequency map was determined with extracellular horseradish peroxidase tracing in relation to quantitative morphological data obtained with light, scanning and transmission electron microscopy. These data reveal distinct species characteristic specializations clearly separate from the patterns observed in other bats with either broad-band or narrow-band sonar systems. The basilar membrane (BM) is coiled to 2.5 turns and about 12 mm long. Its thickness and width only change within the extreme basal and apical ends. The frequency range from about 30 to 80 kHz is represented in the lower basal turn with a typically mammalian mapping coefficient of about 3 mm/octave. This region exhibits morphological features correlated with non-specialized processing of high frequencies. (1) The BM is radially segmented by thickenings of pars tecta and pars pectinata. (2) The 3 rows of outer hair cells (OHCs) have similar morphology. Between 35 and 86% distance from base, frequencies between 30 and 12 kHz are represented with a slightly expanded mapping coefficient of about 6 mm/octave. In analogy to previous work, this cochlea region is termed ‘acoustic fovea’. It includes the frequency range of maximum sensitivity and sharpest tuning (21–27 kHz) but also frequencies below the sonar signals. The fovea is characterized by several morphological specializations. (1) The BM features a continuous radial thickening mainly composed of hyaline substance. (2) There is an increased number of layers of tension fibroblasts in the spiral ligament. (3) There are morphological differences in the arrangements of stereocilia bundles among the 3 rows of OHCs. The transitions between non-specialized and specialized cochlear regions occur gradually within a distance of about 600 μm. The gradients in stereocilia length of both receptor cell types and the gradations in length of the OHC bodies match specialized aspects of the frequency map.

Physiology of primary saccular afferents of goldfish: implications for Mauthner cell response.

Mauthner cells receive neurally coded information from the otolith organs in fishes, and it is most likely that initiation and directional characteristics of the C-start response depend on this input. In the goldfish, saccular afferents are sensitive to sound pressure (< -30 dB re: 1 dyne cm-2) in the most sensitive frequency range (200 to 800 Hz). This input arises from volume fluctuations of the swimbladder in response to the sound pressure waveform and is thus nondirectional. Primary afferents of the saccule, lagena, and utricle of the goldfish also respond with great sensitivity to acoustic particle motion (< 1 nanometer between 100 and 200 Hz). This input arises from the acceleration of the fish in a sound field and is inherently directional. Saccular afferents can be divided into two groups based on their tuning: one group is tuned at about 250 Hz, and the other tuned between 400 Hz and 1 kHz. All otolithic primary afferents phaselock to sinusoids throughout the frequency range of hearing (up to about 2 kHz). Based on physiological and behavioral studies on Mauthner cells, it appears that highly correlated binaural input to the M-cell, from the sacculi responding to sound pressure, may be required for a decision to respond but that the direction of the response is extracted from small deviations from a perfect interaural correlation arising from the directional response of otolith organs to acoustic particle motion.