Sine-wave Bursts Research Articles

Amorphous threshold switch response to pulse burst waveforms

The switching response of thin-film amorphous chalcogenide threshold switches to pulse bursts of sine waves and square waves is reported. For the waveforms and devices investigated, preswitching behavior as evidenced by the delay time is a function of the rms voltage applied to the device. Switching voltages were slightly greater than the minimum required for switching.

Properties of waves guided by a plasma column as determined by time-of-flight measurements

The authors describe experiments designed to investigate several properties of waves which are guided by a plasma column using time-of-flight techniques. The properties which are described are: (a) dispersion of a sine-wave burst; (b) Response to a short voltage impulse (delta function); (c) Reflection properties: and (d) Measurement of the electron drift velocity in the tube.

Journal of the acoustical society of America : Analysis and measurement of ultrasound backscattering from an ensemble of scatterers excited by sinewave bursts Sigelmann, R.A., Reid, J.M. 53 (May 1973) 1351–1355

Journal of the acoustical society of America : Analysis and measurement of ultrasound backscattering from an ensemble of scatterers excited by sinewave bursts Sigelmann, R.A., Reid, J.M. 53 (May 1973) 1351–1355

Analysis and measurement of ultrasound backscattering from an ensemble of scatterers excited by sine-wave bursts

This paper develops a practical approximation for the backscattering of periodic bursts of sine waves by a volume of randomly distributed scatterers. The approximation is applied to the measurement of a “volumetric backscattering cross section,” using a substitution method in which the rms value of the gated backscattered signal is compared with the rms value of a wave reflected from a target of known coefficient of reflection. It is shown that the signal backscattered from the ensemble depends on the attenuation of the wave in the volume and upon the burst and gate lengths. An equation to obtain the volumetric backscattering cross section from experimental data is derived.

Time of flight studies of propagating electrostatic longitudinal waves in an homogeneous plasma

Describes an experimental measurement of the time of flight of a high frequency electrostatic longitudinal sine wave burst through a hot, homogeneous and isotropic plasma. The group velocity of the pulse was measured with a good accuracy for frequencies higher than 1.2 times the plasma frequency (fp). For frequencies between fp and 1.2 fp (in this range the plasma is a high dispersive medium), and for small distances of propagation, up to 2 wavelengths the pulse maximum travels with a velocity lower than the group velocity, in good agreement with numerical calculation. For larger distances of propagation, the sine wave burst splits into 2 pulses: the first pulse seems to be due to the propagation of electron-ballistic waves, while the second one is characteristic of the principal Landau poles.

A time-of-flight study of waves guided by a plasma column

Describes an experiment designed to measure the group velocity of waves guided by a plasma column. Using very short high frequency sine wave burst signals, we were able to perform a time-of-flight experiment. The dependence of the group velocity on ( omega pe(r)) was directly obtained.

Propagation of Low-Frequency Electrostatic Waves in a Magnetic Field

The properties of low-frequency electrostatic waves propagating at various angles to a magnetic field in a plasma are studied. Numerical calculations are used to determine the phase velocities, group velocities, damping decrements, and propagation directions for frequencies between zero and twice the ion cyclotron frequency. A model is presented which simulates experimental time-of-flight studies of finite wave packets generated by sine wave bursts.

Dispersion of Ion-Acoustic Waves

The dispersion of ion-acoustic waves in quiescent rare-gas discharge plasmas has been investigated experimentally and theoretically. Experimentally, various grid systems were used to generate the waves which were studied using a time-of-flight technique. The experimental results show that two separate propagating phenomena appear. The slower propagating disturbance is the ion-acoustic wave, obeying the theoretically predicted dispersion behavior. The faster propagating disturbance, though superficially resembling a wave, is composed of bursts of ions produced by the driving potentials placed on the grids and would appear to be related to the “free streaming” term found by Landau. Previous theoretical models of ion-wave propagation have untilized either purely initial-value or steady-state, boundary-value calculations. A model is presented which more nearly simulates the experimental time-of-flight studies of finite packets of ion waves generated by finite sine-wave bursts.

Time-of-Flight Studies of Propagating Electron Plasma Waves in Tonks-Dattner Resonances

We describe here a series of time-of-flight experiments designed to investigate propagating electron plasma waves in a dc mercury-vapor discharge based upon the development of a phase-coherent nanosecond sine-wave burst. Signals of appreciable amplitude are observed to propagate with a finite velocity on the order of the electron thermal velocity and can be damped by increasing the electron neutral collision frequency. Multiple reflections of the signal are also detected.

Experimental Determination of the Fourth Sound Velocity in Helium II

Fourth sound is a pressure and density wave in He II, in which only the superfluid is in motion. Using packed rouge to lock the normal fluid, the existence of this wave mode has been experimentally confirmed by measuring the temperature dependence of a plane-wave resonance in a closed-closed cylindrical acoustic resonator. The measured phase velocity has a temperature dependence which agrees within 1% with that predicted theoretically. Pulse measurements using 40-kc/sec sine-wave bursts further corroborate the existence of this type of wave. The absolute value of the fourth sound velocity is affected by the coherent multiple scattering of the wave from the superleak material. The results of Twersky's and Saxon's scattering theories are compared with the data. It is found that the equation $n={(2\ensuremath{-}P)}^{\frac{1}{2}}$, where $n$ is the index of refraction and $P$ is the porosity, fits the data within 3%. Values of the ratio of the superfluid to the He II density, derived from the fourth-sound data, agree within 2% with those obtained by other experimental techniques.

Fluctuations in the Reflectivity of the Ocean Surface

An experiment was performed in a deep-ocean basin to investigate the reflectivity of the ocean surface. Acoustic pulses were produced at depths ranging from 500 to 3000 ft and received on hydrophones at a variety of depths and horizontal ranges. The pulses were produced by gating 60-msec bursts of sine waves into sources having resonant frequencies of 170, 400, 600, and 1300 cps. Simultaneous measurements of the ocean-surface waves were made with light buoys (Splashniks) which carried accelerometers. The level of the reflected acoustic energy varies markedly from pulse to pulse. Autocorrelation of successive levels yields a power spectrum which resembles that of the ocean waves. Defining fluctuation as the ratio of the standard deviation of ∫ρ2dt to the average value of ∫ρ2dt, we find that fluctuation increases with acoustic frequency, approaching a saturation value of about 100% when the acoustic wavelength is 4 times the product of the rms height of the ocean waves and the cosine of the angle of incidence θ. Below saturation, the fluctuation is proportional to (cos θ)n, where 0.75<n<1.53 and where n decreases with increasing frequency. [Columbia University, Hudson Laboratories Informal Documentation No. 5. This work was supported by the Office of Naval Research.]

Experimental Case Study of a “Tone-Deaf” Individual

In an experiment started for another purpose, we encountered an observer who was unable to discrimate differences in frequencies of short bursts of sine waves. We then diverted our procedure to conduct an experimental case study comparing the “tone-deaf” observer to three observers with normal frequency discrimination under a variety of experimental conditions. In amplitude-discrimination experiments and experiments in which he is detecting pulses of sine waves he compares favorably. He far surpasses the other three observers when the signal is a sample of “white Gaussian” noise. The comparison of this observer's behavior under binaural and monaural listening conditions is also reported.

Transient Response of Loudspeaker Paper Diaphragms

Response curves of loudspeakers have irregularities, mostly not visible in the case of a loudspeaker of good quality and measured with normal equipment. By enlarging the ordinate scale these small peaks and dips of ±2 db become visible, but with the design of a cone it is considered that these irregularities are more or less inevitable and not so serious. This opinion is strengthened because by listening tests with a variable audio-frequency nothing abnormal can be detected. It is also impossible to measure any distortion in the region of these peaks and dips. By introducing short and sharp bursts of sine waves, however, all sorts of spurious oscillations between the bursts are visible on a cathode-ray tube. The amplitude of these phenomena depends on the internal damping of the diaphragm, the choice of the fiber, and the degree of beating of the pulp. The purpose of this paper is to raise the following question: Is this phenomenon the cause of the apparent harshness, etc., when listening to high-level high-note reproduction?