Frequency specificity of human auditory brainstem responses as revealed by pure-tone masking profiles

The frequency specificity of the auditory brainstem response (ABR) was examined by means of pure-tone masking profiles using click, 4000-Hz, and 1000-Hz filtered-click stimuli. Simultaneous pure-tone maskers were presented at one-half octave intervals around stimulus center frequency. Masking profiles at two intensities (60 and 40 dB SL) were obtained by measuring both latency and amplitude shifts in wave V as a result of the discrete-frequency maskers. Both latency and amplitude analyses showed masking profiles at 40 dB SL that were narrow and centered around stimulus frequency, whereas profiles at 60 dB SL showed high-frequency spread of the cochlear excitation area.     

Auditory brain stem responses from human infants: pure-tone masking profiles for clicks and filtered clicks

The effects of simultaneous pure-tone maskers on ABR wave V latency and amplitude were examined in three-month-old infants as a means of delineating the frequency specificity of these responses in the immature auditory system. Masking profiles at two intensities (60 and 40 dBn HL) were obtained for click, as well as 4000- and 1000-Hz filtered-click stimuli. Infant profiles, obtained by measuring both latency and amplitude shifts as a result of the discrete-frequency maskers, were compared to adult data obtained under an identical masking paradigm. Both latency and amplitude analyses showed masking profiles for infants which reveal greater low-frequency contribution to responses than found in adult profiles. Additionally, the infant profiles reveal clear differences in the degree of high-frequency spread of masking when comparisons are made to the adult data.     

Spectral-line asymmetry in double-output-cavity lasers

The aim of this work is to show that the output from a double-output laser cavity exhibits distinctive features, manifesting themselves through typical asymmetry in the corresponding spectral-line shapes. Such asymmetry in an inhomogeneously broadened gas laser usually appears with a clear, but unpredictable shift of the maximum intensity level either towards the high or low frequency sides with respect to line centre. In the case of a double-output laser, the spectral profiles show opposite shifts. This means that when the maximum intensity of one output moves towards the high frequency side of the profile, the maximum intensity of the other moves towards the low frequency side. This gives rise to a frequency shift with respect to the Lamb-dip for a classical laser. On the theoretical side, we apply the standard disturbed Gaussian beam model to provide a quantification of the frequency shifts obtained at both sides of the system.     

Electrostrictive cross-phase modulation of periodic pulse trains in optical fibers

Electrostriction-induced cross-phase modulation between subsequent bits of a nonreturn-to-zero pulse train in optical fibers leads to nonlinear frequency shifts of opposite sign for the 1's and the 0's. Direct experimental measurements of the electrostrictive and Kerr-induced nonlinear phase shift across the bit profiles agree well with the theoretical modeling.     

Multi-photon vibrational resonances,with modulation effects,using HeXe,NeAr and NeXe as models

Model calculations are presented for the multi-photon vibrational spectra for the bound states of the (non-rotating) rare gas dimers HeXe, NeAr and NeXe. The results are used to discuss some of the features of electric dipole spectra that can occur due to the presence of non-zero diagonal dipole matrix elements and/or near-degenerate energy levels. These include multi-photon resonance profiles with oscillatory fringe patterns localized around the main resonance peaks and the possibility of shifts of resonance positions to low frequency relative to the weak field limit.     

Theoretical investigation on the intracavity Doppler effect in continuous wave swept-cavity ringdown spectroscopy

We theoretically investigate the spectral measurement errors that are apt to occur in continuous wave (CW) cavity ringdown (CRD) techniques suffering intracavity Doppler shifts. In the typical CW CRD scheme based on a cavity sweep operation for the resonant coupling of a probe laser into a ringdown cavity, the intracavity probe light detunes gradually over time, carrying time-dependent loss information of an absorption feature. Frequency-drifting ringdown signals are theoretically modelled and found to result in erroneous absorption spectra that exhibit the frequency shift of absorption profiles as well as linewidth broadening. PACS 42.62.Fi; 42.60.Da; 42.25.BS     

Variability of the vertical interference structure of the sound field in a shallow sea

Dynamics of the spectral intensity oscillations that occur in the vertical plane because of the time variability of the medium along the propagation path is described. The errors arising in measuring the frequency shifts of the interference structure are considered. For low-frequency broadband signals received on a stationary propagation path, experimental data on the shifts of their frequency spectra due to the variation of the reception depth are presented. The number of interfering modes and their arrival directions in the vertical plane are estimated from the measured frequency shifts of the spectral intensity oscillation.     

Polarization control method for ultraviolet writing of advanced Bragg gratings

We present a flexible and simple method for UV writing of Bragg gratings with advanced apodization profiles including discrete phase shifts. The method is based on a p phase shift between the refractive-index modulation profiles induced by s and p polarization of UV light. By changing the ratio of UV intensity in the two polarizations we are able to control the modulation strength and to induce phase shifts while keeping a constant effective refractive index throughout the Bragg grating. We demonstrate strong UV-written Bragg gratings with Gaussian or sinc apodizations with spectral shapes, in good agreement with theoretical predictions.     

Automatic correction for phase shifts, frequency shifts, and lineshape distortions across a series of single resonance lines in large spectral data sets

A new model-free method is presented that automatically corrects for phase shifts, frequency shifts, and additional lineshape distortions of one single resonance peak across a series of in vivo NMR spectra. All separate phase and frequency variations are quickly and directly derived from the common lineshape in the data set using principal component analysis and linear regression. First, the new approach is evaluated on simulated data in order to quantitatively assess the phase and frequency shifts which can be removed by the proposed correction procedure. Subsequently, the value of the method is demonstrated on in vivo (31)P NMR spectra from skeletal muscle of the hind leg of the mouse focusing on the phosphocreatine resonance which is distorted by the experimental procedure. Phase shifts, frequency shifts, and lineshape distortions with respect to the common lineshape in the spectral data set could successfully be removed.     

Spatial interference of normal waves in oceanic waveguides

Expressions are derived for the frequency shifts of interference maxima that occur at separate observation points because of a two-dimensional anisotropic random perturbation of the oceanic medium. A relation between the frequency shifts of the field maxima at the observation points and the variations in the phase differences between interfering normal waves is revealed. The use of the frequency shifts in solving direct problems of wave propagation is discussed.     

Performance of profiled single noise barriers covered with quadratic residue diffusers

The paper describes an investigation about the acoustic performance of noise barriers with quadratic residue diffuser (QRD) tops, and with T-, Arrow-, Cylindrical and Y-shape profiles. A 2D boundary element method (BEM) is used to calculate the barrier insertion loss. The results of rigid and with absorptive coverage are also calculated for comparisons. Using QRD on the top surface of almost all barrier models presented here is found to improve the efficiency of barriers compare with using absorptive coverage at the examined receiver positions. T-shape and Arrow-shape barriers are also found to provide better performance than other shapes of barriers. The best shape of barriers for utilising QRD among the tested models is the T-shape profile barrier. It is found that reducing the design frequency of QRD shifts the performance improvement towards lower frequency, and therefore the most efficient model for traffic noise is a barrier covered with a QRD tuned to around 400 Hz.     

Iodine stabilized He-Ne laser with a hot wall iodine cell

We describe experiments we have done with a hot wall iodine cell He-Ne laser. The net result is an improvement of the contrast of the saturated absorption peak which is used for frequency stabilization. The frequency shifts induced by collisions are measured. Anomalous modulation width dependent frequency shifts are observed in some cases.     

High sensitive determination of laser-induced frequency shifts of ultracold cesium molecules

We experimentally present a technique for sensitively determining the laser-induced frequency shifts of the long-range molecular vibrational and rotational levels. The scheme relies on an optical frequency shifter, leading to two laser beams with a precise and adjustable frequency interval. A series of photoassociation spectra are recorded with both beams inducing molecular lines, whose peak separation provides an accurate frequency ruler to measure the frequency shifts of cesium molecular levels, which have not yet been observed in previous reports. The data are compared to theoretical predictions and show a good agreement.     

The possibility of reconstruction of two-dimensional random inhomogeneities in a shallow sea by frequency shifts of the spatial interference structure of the sound field

Fluctuations of frequency shifts of the spatial interference structure of the sound field in the oceanic waveguide, caused by a two-dimensional field of a random perturbation, are described. Various schemes of observation point spacing are considered. The possibility is shown to reconstruct the spatial spectrum of waveguide perturbations by measuring the spatial spectrum of the frequency shift of the interference pattern. The results of the theoretical treatment are illustrated by the examples of background internal waves and bottom roughness. The sensitivity of monitoring based on measurements of frequency shifts of the interference structure of the sound field is estimated. For medium perturbations by background internal waves, the fluctuations of liquid layer vibrations, sound speed, and temperature, which are minimum detectable by frequency shifts of the interference pattern, were estimated.     

Electron tuning of frequency in gyrotrons

Formulas for shifts of gyrotron autooscillation frequency due to change of electron beam parameters are presented. The frequency shifts can be commensurable with the frequency band of the beam-unloaded cavity. The autooscillation frequency is most sensitive to the change of the magnetic field, less to the change of the anode voltage and least to the the change of the beam voltage. Experiments presented are in satisfactory agreement with the theory.The authors wish to thank M.I. Petelin for his interest to the present work.     

Frequency shifts of sound field maxima in oceanic waveguides

The frequency shifts of sound field maxima that are caused by the variability of the medium in an oceanic waveguide are described. The condition under which the time spectrum of the frequency shifts of interference maxima is proportional to the time spectrum of fluctuations in the dispersion characteristic of the waveguide is determined.     

Correlation effects in the theory of combined doppler and pressure broadening—I. Classical theory

A classical Fourier amplitude theory of combined Doppler and pressure broadening in the impact approximation is developed which treats phase changes changes due ti translation and collision on an equal basis. Radiator motion is accounted for properly by including speed dependence in the collision frequency and velocity dependence in the distribution function for phase shifts and final velocities as the result of a collision. The resulting theory is shown to be equivalent to a previous kinetic equation formulation of the problem. The one-perturber and classical analogue of the quantum one-interacting-level approximations are derived. In the latter case, a simple expression for the line shape in terms of speed dependent width and shift functions is obtained without approximation. Correlation effects are investigated by means of model speed dependent width and shift functions calculated for an inverse power interaction using straight line trajectories. The model shows no departure from a Voigt profile for the r^-3 interaction and for the r^-6 and r^-12 interactions the resulting profile is narrower in the core than the Voigt and in general asymmetric. Analysis of correlated profiles as Voigt profiles is shown under some conditions to lead to non-linear density dependence in the width and shifts resulting in extra- polation anomalies and to significant errors in temperatures inferred from Doppler widths. Results are compared with previous work.     

Frequency shifts in parametrically enhanced low-field MR detection

A high-amplitude, high-frequency readout field has previously been proposed for use with low-field MR. Because the resulting modulation sidebands are at higher frequencies than the low-field steady precession, improved detection sensitivity results. However, if the ac readout field is inhomogeneous, it will necessarily have transverse components resulting in frequency shifts and broadening of the MR signal. Numerical solutions of Bloch's equations are compared to the Bloch-Siegert result to assess the size of the frequency shifts. A formula is derived by the average Hamiltonian method and provides an excellent fit to the numerically obtained shifts.     

Resonance shifts in ABMR due to inhomogeneities of the magnetic and rf-fields

On the basis of the non-relativistic time dependent Schrödinger theory shifts of the resonance frequency due to an arbitrary inhomogeneity of the rf-field with respect to amplitude, direction and phase, and shifts due to small inhomogeneities of the magnetic field are considered. A general relation is derived by which one can find the appropriate experimental methods to determine the shifts without a detailed knowledge of the actual line shapes. Usually small effects as shifts due to non-constant field direction or due to neighbouring states are included in the formalism. The results have been used successfully in precision experiments in which frequency shifts of about 10^?2 of the resonance width were eliminated up to a few 10^?5.     

Decoupling of auditory pitch and stimulus frequency: the Shepard demonstration revisited

With ten successive octave tones, Shepard demonstrated that upward shifts in frequency might be heard as downward shifts in pitch. This decoupling of auditory pitch and frequency has important consequences for any representational theory of pitch. Experiments are reported that attempt to identify the crucial features of Shepard's demonstration.