Time Delay Changes Research Articles

Direct measurement of surface wave velocity and time delay—Temperature variation using a pulse technique

An experimental pulse technique has been developed permitting rapid measurement of absolute surface wave velocity on single crystals to an accuracy of 1 percent or better. A further modification of the technique allows measurement of parts per million changes in surface wave time delay caused by changes in substrate temperature. The technique directly measures the vertical component of particle velocity at the receiver as a function of time and enables one to distinguish clearly between the various types of surface modes, e.g., Rayleigh wave, pseudosurface wave, etc. The method is applicable to any material.

Investigation of the switching characteristics of the TeAsGeSi glass-films

Thin-film switches have been investigated by pulse techniques. We have pointed out that the energy controlled switching model is more general than the threshold voltage, holding current model. The delay time is given by tD = K1 exp (− V/K2) for the voltage dependence, and tD = K3 (lnK4/f) for the repetition rate dependence. The delay time change is least sensitive to pulse width.

A photographic method for the recording of specimen behaviour during rapid fracture tests

Time delay twin flash photography has been applied to the observation of small scale impact test specimens during fracture. Incremental changes in delay time in successive identical tests yield a series of photographs from which a continuous surface behaviour throughout fracture can be implied.

Spatial Chords

A spatial chord is similar to a conventional musical chord, except that the component tones differ in spatial position as well as in pitch. Spatial chords of this type were simulated using binaural techniques. Five simultaneous tones at frequencies of 250, 297, 354, 421, and 500 cps were presented dichotically, each tone having an associated interaural delay of either −1.0, −0.5, 0, 0.5, or 1.0 msec; negative values indicate delay to the left ear. This stimulus corresponds to a chord of tones spaced at minor-third intervals where the spatial positions of the tones are distributed between the two ears. Different spatial chords were obtained by keeping the tonal frequencies fixed but interchanging the associated interaural delays. Each of the spatial chords was heard as a fused sound of a gestaltlike character. An AB test between various pairs of chords of 500 msec duration was performed. Differences in the spatial arrangement of the component tones were perceived as changes in the quality of the resulting chord. Ease of discrimination depended on the total sum of changes in interaural time delay.

Measurement of Very Small Changes in the Velocity of Sound in Solids

Apparatus for measuring very small changes in delay time or velocity of ultrasonic waves in solids is described. The long-term stability of the electronic system and a resolution of approximately one part in ten million for high-Q materials extend the usefulness of the equipment. By way of illustration, some results for delay-time variations for ultrasonic waves in single crystals under small uniaxial stress are presented. Also, the determination of shear mechanical properties of low-viscosity liquids by the shear-reflectance method is described.

Comparison of the masked thresholds of a simulated moving and stationary auditory signal.

The masked thresholds of a simulated moving signal produced by a linear stepwise change in interaural time delay and with movement at two different locations in the phenomenal field were compared with the thresholds obtained with a stationary signal. Using a noise band extending from 75 to 850 cps as the signal and presented against a heterophasic background noise, masked thresholds were made under the following conditions: (1) signal moving at a perceptually slow and fast rates, (2) a perceptually fast moving signal with the signal making four excursions across the phenomenal field during each presentation period, (3) with the signal movement controlled by the observer, and (4) during an extended listening period in which the observer was given no cue as to when the signal was to be presented. The results of the threshold comparisons with these different conditions indicate that the masked threshold of a moving signal is a function only of its localization at any given instant in time and that a moving signal does not elicit a lower masked threshold than a stationary signal.

Comparison of the Masked Thresholds of a Simulated Moving and Stationary Auditory Signal

The masked thresholds of a simulated moving signal produced by a linear stepwise change in interaural time delay and with movement at two different locations in the phenomenal field were compared with the thresholds obtained with a stationary signal. Using a noise band extending from 75 to 850 cps as the signal and presented against a heterophasic background noise, masked thresholds were made under the following conditions: (1) signal moving at a perceptually slow and fast rates, (2) a perceptually fast moving signal with the signal making four excursions across the phenomenal field during each presentation period, (3) with the signal movement controlled by the observer, and (4) during an extended listening period in which the observer was given no cue as to when the signal was to be presented. The results of the threshold comparisons with these different conditions indicate that the masked threshold of a moving signal is a function only of its localization at any given instant in time and that a moving signal does not elicit a lower masked threshold than a stationary signal.

SHOT HOLE CHARACTERISTICS IN REFLECTION SEISMOLOGY

The influence of shot‐hole characteristics on seismograms is discussed in some detail. Modifications in the formations surrounding the shot‐hole caused by successive shots result in compaction or aeration affecting changes in delay times as well as changes in character of the recorded events. The importance of considering these effects in the interpretation of seismograph records and some methods of alleviating these problems by suitable field technique are discussed.