scholarly journals On measurement of reverberation chamber time constant and related curve fitting techniques

2015 ◽  
Author(s):  
Xiaotian Zhang ◽  
Martin Robinson ◽  
Ian Flintoft
Keyword(s):  
Time Constant ◽  
Curve Fitting ◽  
Reverberation Chamber

Exponential Modeling of Frequency-Following Responses in American Neonates and Adults

2018 ◽  
Vol 29 (02) ◽  
pp. 125-134 ◽  
Author(s):  
Fuh-Cherng Jeng ◽  
Brandie Nance ◽  
Karen Montgomery-Reagan ◽  
Chia-Der Lin
Keyword(s):  
Time Constant ◽  
Curve Fitting ◽  
Speech Processing ◽  
Phase Locking ◽  
Pitch Contour ◽  
Frequency Error ◽  
Tracking Accuracy ◽  
Exponential Curve ◽  
Adult Participants ◽  
Fitting Model

AbstractThe scalp-recorded frequency-following response (FFR) has been widely accepted in assessing the brain’s processing of speech stimuli for people who speak tonal and nontonal languages. Characteristics of scalp-recorded FFRs with increasing number of sweeps have been delineated through the use of an exponential curve-fitting model in Chinese adults; however, characteristics of speech processing for people who speak a nontonal language remain unclear.This study had two specific aims. The first was to examine the characteristics of speech processing in neonates and adults who speak a nontonal language, to evaluate the goodness of fit of an exponential model on neonatal and adult FFRs, and to determine the differences, if any, between the two groups of participants. The second aim was to assess effective recording parameters for American neonates and adults.This investigation employed a prospective between-subject study design.A total of 12 American neonates (1–3 days old) and 12 American adults (24.1 ± 2.5 yr old) were recruited. Each neonate passed an automated hearing screening at birth and all adult participants had normal hearing and were native English speakers.The English vowel /i/ with a rising pitch contour (117–166 Hz) was used to elicit the FFR. A total of 8,000 accepted sweeps were recorded from each participant. Three objective indices (Frequency Error, Tracking Accuracy, and Pitch Strength) were computed to estimate the frequency-tracking acuity and neural phase-locking magnitude when progressively more sweeps were included in the averaged waveform. For each objective index, the FFR trends were fit to an exponential curve-fitting model that included estimates of asymptotic amplitude, noise amplitude, and a time constant.Significant differences were observed between groups for Frequency Error, Tracking Accuracy, and Pitch Strength of the FFR trends. The adult participants had significantly smaller Frequency Error (p < 0.001), better Tracking Accuracy (p = 0.001), and larger Pitch Strength (p = 0.003) values than the neonate participants. The adult participants also demonstrated a faster rate of improvement (i.e., a smaller time constant) in all three objective indices compared to the neonate participants. The smaller time constants observed in adults indicate that a larger number of sweeps will be needed to adequately assess the FFR for neonates. Furthermore, the exponential curve-fitting model provided a good fit to the FFR trends with increasing number of sweeps for American neonates (mean r 2 = 0.89) and adults (mean r 2 = 0.96).Significant differences were noted between the neonatal and adult participants for Frequency Error, Tracking Accuracy, and Pitch Strength. These differences have important clinical implications in determining when to stop a recording and the number of sweeps needed to adequately assess the frequency-encoding acuity and neural phase-locking magnitude in neonates and adults. These findings lay an important foundation for establishing a normative database for American neonates and adults, and may prove to be useful in the development of diagnostic and therapeutic paradigms for neonates and adults who speak a nontonal language.

scholarly journals Efficient Determination of Reverberation Chamber Time Constant

2018 ◽  
Vol 60 (5) ◽  
pp. 1296-1303 ◽  
Author(s):  
Xiaotian Zhang ◽  
Martin P. Robinson ◽  
Ian D. Flintoft ◽  
John F. Dawson
Keyword(s):  
Time Constant ◽  
Reverberation Chamber

scholarly journals Approximation and analysis of transient responses of a reverberation chamber by pulsed excitation

2020 ◽  
Vol 18 ◽  
pp. 53-73
Author(s):  
Konstantin Pasche ◽  
Fabian Ossevorth ◽  
Ralf T. Jacobs
Keyword(s):  
Spectral Analysis ◽  
Steady State ◽  
Time Constant ◽  
Time Domain ◽  
Linear Time ◽  
System Response ◽  
Transient Field ◽  
Reverberation Chamber ◽  
Transient Behaviour ◽  
The Time Domain

Abstract. Reverberation chambers show transient behaviour when excited with a pulsed signal. The field intensities can in this case be significantly higher than in steady state, which implies that a transient field can exceed predefined limits and render test results uncertain. Effects of excessive field intensities of short duration may get covered and not be observable in a statistical analysis of the field characteristics. In order to ensure that the signal reaches steady state, the duration of the pulse used to excite the chamber needs to be longer than the time constant of the chamber. Initial computations have shown that the pulse width should be about twice as long as the time constant of the chamber to ensure that steady state is reached. The signal is sampled in the time domain with a sampling frequency according to the Nyquist theorem. The bandwidth of the input signal is determined using spectral analysis. For a fixed stirrer position, the reverberation chamber, wires, connectors, and antennas can jointly be considered as a linear time-invariant system. In this article, a procedure will be presented to extract characteristic signal properties such as rise-time, transient overshoot and the mean value in steady state from the system response. The signal properties are determined by first computing the envelope of the sampled data using a Hilbert transform. Subsequent noise reduction is achieved applying a Savitzky–Golay filter. The point where steady state is reached is then computed from the slope of the envelope by utilising a cumulative histogram. The spectral analysis is not suitable to examine the transient behaviour and determine the time constants of the system. These constants are computed applying the method of Prony, which is based on the estimation of a number of parameters in a sum of exponential functions. An alternative to the Prony Method is the Time-Domain Vector-Fit method. In contrast to the first mentioned variant, it is now also possible to determine the transfer function of the overall RC system. Differences and advantages of the methods will be discussed.

scholarly journals DC Motor Parameter Identification Using Speed Step Responses

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Wei Wu
Keyword(s):  
Power Series ◽  
Time Constant ◽  
Curve Fitting ◽  
Power Series Expansion ◽  
Dc Motor ◽  
Motor Speed ◽  
Response Measurement ◽  
Step Voltage ◽  
Motor Parameter ◽  
Speed Response

Based on the DC motor speed response measurement under a step voltage input, important motor parameters such as the electrical time constant, the mechanical time constant, and the friction can be estimated. A power series expansion of the motor speed response is presented, whose coefficients are related to the motor parameters. These coefficients can be easily computed using existing curve fitting methods. Experimental results are presented to demonstrate the application of this approach. In these experiments, the approach was readily implemented and gave more accurate estimates than conventional methods.

The Effect of Sensori-Neural Hearing Loss on Threshold-Duration Functions

1968 ◽  
Vol 11 (4) ◽  
pp. 842-852 ◽  
Author(s):  
H. N. Wright
Keyword(s):  
Hearing Loss ◽  
Differential Diagnosis ◽  
Time Constant ◽  
Present Series ◽  
Auditory Disorders ◽  
Threshold Duration

Previous findings on the threshold for tones as a function of their duration have suggested that such functions may be systematically affected by sensori-neural hearing losses of cochlear origin. The present series of investigations was designed to explore this relation further and to determine also whether the amount of hearing loss present has any effect upon the results which are obtained. Preliminary studies were also carried out on a conductively impaired listener to indicate whether hearing losses of this type affect the threshold-duration function. The results indicate that the threshold-duration function is systematically affected by sensori-neural hearing losses of cochlear origin. This effect is manifested by a progressive shortening of the time constant relating threshold to duration and is not uniquely related to the amount of hearing loss present. The results obtained from the conductively impaired listener suggested that this type of hearing loss has no effect on the threshold-duration function, thereby implying that such functions may contribute significantly to the differential diagnosis of auditory disorders.

Estimating ink mileage of dry toners in electrophotography

TAPPI Journal ◽  
2013 ◽  
Vol 12 (3) ◽  
pp. 9-14
Author(s):  
RENMEI XU ◽  
CELESTE M. CALKINS
Keyword(s):  
Experimental Data ◽  
Curve Fitting ◽  
Graphite Furnace ◽  
Atomic Absorption Spectrometer ◽  
Density Region ◽  
Coated Papers ◽  
Graphite Furnace Atomic Absorption ◽  
S Model ◽  
Better Than ◽  
Film Weight

This work investigates the ink mileage of dry toners in electrophotography (EP). Four different substrates were printed on a dry-toner color production Xerox iGen3 EP press. The print layout contained patches with different cyan, magenta, yellow, and black tonal values from 10% to 100%. Toner amounts on cyan patches were measured using an analytical method. Printed patches and unprinted paper samples, as well as dry toners, were dissolved in concentrated nitric acid. The copper concentrations in the dissolved solutions were analyzed by a Zeeman graphite furnace atomic absorption spectrometer. Analytical results were calculated to determine the toner amounts on paper for different tonal values. Their corresponding reflection densities were also measured. All data were plotted with OriginPro® 8 software, and four mathematical models were used for curve fitting. It was found that the C-S model fitted the experimental data of the two uncoated papers better than the other three models. None of the four models fitted the experimental data of the two coated papers, while the linear model was found to fit the data well. Linear fitting was the best in the practical density region for the two coated papers. Ink mileage curves obtained from curve fitting were used to estimate how much ink was required to achieve a target density for each paper; hence, the ink mileage was calculated. The highest ink mileage was 3.39 times the lowest ink mileage. The rougher the paper surface, the higher the requirement for ink film weight, and the lower ink mileage. No correlation was found between ink mileage and paper porosity.

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