Narrow Band Frequency Analysis Research Articles

Calibration of sound power sources: Current status and new developments.

Reference sound sources used in sound power measurements are currently calibrated according to well-documented techniques. Low frequency limitations and solely broadband analysis restrict the applicability of these methods. The concept of traceability is introduced to overcome these deficiencies. This study presents the calibration of reference sound sources through a measurement chain, which is based on the substitution method. The applicability of the substitution method extends to sound intensity measurements and narrowband frequency analysis. A specially designed apparatus allows the detection of the sound field over a fully scanned hemisphere. The results of the apparatus are comparable to the results of the existing methods. The substitution method reduces the required corrections, which are presented. The sound power levels are supplemented by a transparent uncertainty budget, which allows the estimation of each uncertainty component individually. The comparison between the methods is also given in terms of a confidence interval.

ВИБРОНАЛАДКА ЭЛЕКТРОМАШИННЫХ ПРЕОБРАЗОВАТЕЛЕЙ С ТЕХНОЛОГИЧЕСКИМИ ДЕФЕКТАМИ, ОГРАНИЧИВАЮЩИМИ КАЧЕСТВО БАЛАНСИРОВКИ

The present-day production and repair of vessels imply saving costs and retaining output quality. One of the cost items is maintenance of processing equipment of manufacturing plants with minimal expense. It can be implemented using up-to-date engineering diagnostics. Suggested tool equipment of vibration diagnostics and vibration adjustment allow not only controlling true technical state of electrical machine, but bring vibration level to target values. The set of methods, including RMS level vibration measuring, narrow-band frequency analysis and spectrum of envelope of vibration, provide insight into complete idea of true technical state of rotor equipment. Vibration adjustment methods, such as alignment, frame flatness setting-out, frame hardening, allow successfully to perform the balancing procedures. The article presents the symptoms of the most widespread defects of rotary converters, which are affected to perform mechanism balancing. Methods of successive elimination of revealed defects are described in detail by the example of converter vibration adjustment. According to the analysis results, application of methods and facilities of vibration diagnostics and vibration adjustment allow to significantly increase repair intervals and, as a consequence, to decrease costs of motor-operated mechanism repair.

Multi-fiber coding on the auditory nerve and the origin of critical-band masking

Understanding the physiological mechanisms that underlie the exquisite frequency discrimination abilities of listeners remains a central problem in auditory science. We describe a computational model of the cochlea and auditory nerve that was developed to evaluate the frequency analysis capabilities of a system in which the output of a basilar membrane filter, transduced into a probability-of-firing function by an inner hair cell, is encoded on the auditory nerve as the instantaneous sum of firings on a critical band of fibers surrounding that filter channel and transmitted to the central nervous system for narrow-band frequency analysis. Performance of the model on vowels over a wide range of input levels was found to be robust and accurate, comparable to the Average Localized Synchronized Rate results of Young and Sachs [J. Acoust. Soc. Am. 1979, 66, 1381-1403]. Model performance in perceptual threshold simulations was also evaluated. The model succeeded in replicating psychophysical results reported in classic studies of critical band masking.

Explicit symplectic orbit and spin tracking method for electric storage ring

We develop a symplectic charged particle tracking method for phase space coordinates and polarization in all electric storage rings. Near the magic energy, the spin precession tune is proportional to the fractional momentum deviation ${\ensuremath{\delta}}_{m}$ from the magic energy, and the amplitude of the radial and longitudinal spin precession is proportional to $\ensuremath{\eta}/{\ensuremath{\delta}}_{m}$, where $\ensuremath{\eta}$ is the electric dipole moment for an initially vertically polarized beam. The method can be used to extract the electron electric dipole moment of a charged particle by employing narrow band frequency analysis of polarization around the magic energy.

Unusual echolocation behavior in a small molossid bat, Molossops temminckii, that forages near background clutter

When searching for flying insects, Molossops temminckii uses unusual echolocation calls characterized by upward modulation of frequency vs time (UFM). Call frequency increases asymptotically in the relatively long (∼8 ms) pulses from a starting frequency of ∼40 kHz to a long narrowband tail at ∼50 kHz. When approaching a prey, the bat progressively increases the duration of calls and intersperses in the sequence broadband downwardly frequency-modulated signals with a terminal frequency of about 53 kHz, which totally replaces the UFM signals at the end of the approach phase. The sequence progresses to a capture buzz resembling those from other molossid and vespertilionid bats. The M. temminckii wing morphology is characterized by an average aspect ratio and a high wing loading, suggesting that it is more maneuverable than the typical Molossidae but less than typical Vespertilionidae. M. temminckii regularly forages near clutter, where it needs to pay attention to the background and might face forward and backward masking of signals. We hypothesize that the UFM echolocation signals of M. temminckii represent an adaptation to foraging near background clutter in a not very maneuverable bat needing a broad attention window. The broadband component of the signal might serve for the perception of the background and the narrowband tail for detection and perhaps classification of prey. Bats may solve the signal masking problems by separating emission and echoes in the frequency domain. The echolocation behavior of M. temminckii may shed light on the evolution of the narrowband frequency analysis echolocation systems adopted by some bats foraging within clutter.

Tuning the cochlea: wave-mediated positive feedback between cells

Frequency analysis by the mammalian cochlea is traditionally thought to occur via a hydrodynamically coupled 'travelling wave' along the basilar membrane. A persistent difficulty with this picture is how sharp tuning can emerge. This paper proposes, and models, a supplementary or alternative mechanism: it supposes that the cochlea analyses sound by setting up standing waves between parallel rows of outer hair cells. In this scheme, multiple cells mutually interact through positive feedback of wave-borne energy. Analytical modelling and numerical evaluation presented here demonstrate that this can provide narrow-band frequency analysis. Graded cochlear tuning will then rely on the distance between rows becoming greater as distance from the base increases (as exhibited by the actual cochlea) and on the wave's phase velocity becoming slower. In effect, tuning is now a case of varying the feedback delay between the rows, and a prime candidate for a wave exhibiting suitably graded phase velocity-a short-wavelength 'squirting wave'-is identified and used in the modelling. In this way, resonance between rows could supply both amplification and high Q, characteristics underlying the 'cochlear amplifier'-the device whose action has long been evident to auditory science but whose anatomical basis and mode of operation are still obscure.

Narrow-Band Frequency Analysis for Laser-Based Glass Thickness Measurement

This paper presents a narrow-band frequency analysis approach for a new laser interferometric heterodyne system, which is used for noncontact glass bottle wall thickness measurement. The measurement signal consists of a number of spectral components, the strongest of which is a reliable representation of the above-mentioned thickness. A fast method for searching and locating this frequency is vital for real-time implementations. As the standard fast Fourier transform (FFT) proved to be ineffective for the given problem, we use a combination of a zero-padding discrete Fourier transform (DFT) with a coarse-to-fine technique to locate this frequency at a smaller processing cost. Considering also the Chirp-z transform, a comparison of the different methods under investigation demonstrates the effectiveness of the proposed approach for online thickness estimation.

STRUCTURAL INTENSITY CALCULATIONS FOR COMPLIANT PLATE–BEAM STRUCTURES CONNECTED BY BEARINGS

A computational strategy, based on component mobility and modal synthesis approaches, is described to calculate structural power flow through multi-dimensional connections such as rolling element bearings and joints. Research issues are discussed in the context of narrow band frequency analysis methods for vibration energy transmission and dissipation. Through the example case of a beam (shaft), ball bearings and an elastic machinery casing plate, the structural intensity calculation procedure is illustrated. A new pre-synthesis algorithm is outlined which is utilized to determine the effective stiffness of ball bearings while accounting for the compliance of the neighbouring structure. The finite element method is used to facilitate computations and to generate structural intensity results in the post-synthesis mode. Sample results are included along with a discussion of various research issues.

Recent Advances in the Study of Bats

This broadly based volume brings together the twenty-one papers presented at the Seventh International Bat Research Conference in Aberdeen in August 1985 on Flight, Echolocation and Social and Reproductive Biology. These areas of research have seen the most significant advances in recent years and new results are presented and analysed by leading international authorities. The volume includes piipets on the origin, aerodynamics and physiology of flight, on behavioural studies of echolocation including interactions between bats and insects, on narrow band frequency analysis by echolocating bats, on the genetic structure of social groups, alxruism and cooperation, on the energetics of reproduction, and on the activity of the hypothalamo-hypopbyseal-gonad axis in seasonally breeding bats. This volume will be of interest to all who are interested in bats as supreme examples of evolutionary adaptation.

A Study on the Mechanisms of the Generation of the Wheel/Rail Noise and its Transmission to the Vehicle : An Examination based on the Results of Narrow Band Frequency Analysis

We studied on the mechanisms of the generation of the wheel/rail noise and its transmission to the vehicle in high speed operation on an almost straight track like that of SHINKANSEN. Tests were carried out on the SHINKANSEN test track and the results were examined by narrow band frequency analysis. It was concluded that the contribution of the noise due to the vibration of a wheel and a bogie frame to the train noise is small, their damping is not effective and the internal noise is mostly due to the contribution of the air-borne noise transmitted through the floor.

A Study on the Generation of Train Noise and Its Transmission into the Carbody : An Examination Based on Narrow Band Frequency Analysis

A Study on the Generation of Train Noise and Its Transmission into the Carbody : An Examination Based on Narrow Band Frequency Analysis

Spinning Frame Noise Sources

As part of a Coordinated Textile Industry Noise Reduction Program, a study of the sources of spinning frame noise has been conducted. Techniques of source modification and narrow-band frequency analysis were used. Several machines were studied. Major noise sources were found to be the ring-traveler and spindle-bobbin systems. Other sources identified were the drive cylinder, drive tapes, idler pulleys, vacuum system, and gears. Relative importance of the sources and differences among machines is discussed. Suggestions are offered for ways to reduce noise from some of the sources. Work is continuing to evaluate and develop the most feasible methods of spinning frame noise reduction.

The Chirp z-Transform Algorithm and Its Application

We discuss a computational algorithm for numerically evaluating the z-transform of a sequence of N samples. This algorithm has been named the chirp z-transform algorithm. Using this algorithm one can efficiently evaluate the z-transform at M points in the z-plane which lie on circular or spiral contours beginning at any arbitrary point in the z-plane. The angular spacing of the points is an arbitrary constant; M and N are arbitrary integers. The algorithm is based on the fact that the values of the z-transform on a circular or spiral contour can be expressed as a discrete convolution. Thus one can use well-known high-speed convolution techniques to evaluate the transform efficiently. For M and N moderately large, the computation time is roughly proportional to (N + M) log <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (N + M) as opposed to being proportional to N · M for direct evaluation of the z-transform at M points. Applications discussed include: enhancement of poles in spectral analysis, high resolution narrow-band frequency analysis, interpolation of band-limited waveforms, and the conversion of a base 2 fast Fourier transform program into an arbitrary radix fast Fourier transform program.

Use of Constant-Bandwidth Narrow-Band Frequency Analysis to Pinpoint Noise Sources in Machinery

This paper compares the results of the analysis of noise and vibration in machinery by constant-bandwidth filters as narrow as 2 cps with the more conventional octave-band, 13-oct band, and percentage-of-center-frequency filters. The nature and character of the resulting noise spectra are used to pinpoint machinery noise sources. The technique described involves instrumentation-quality tape recording of noise emanating from a machine, followed by analysis of the tape in the laboratory with narrow-band scanning filters and direct plotting of the results on X-Y plotters. In some studies, the interdependence of noise and vibration has been determined by simultaneously recording both signals and making an analysis. Comparisons between these narrow-band vibration and noise spectra give new insight into the dynamic behavior of machines.