Relation of Earphone Transient Response to Measurement of Onset-duration. Rep 63-7.

Measurements were made of the transient response of PDR-8 earphones. These data indicate that the original estimate of the onset-duration of auditory stimuli can be revised downward to 0.8 ms. Implicit in the results is a caveat on the faith one should have in the output of commonly used earphones with shortor single-transient inputs. Onset-duration, the duration below which only cues derived from the onset of a stimulus are effective, was first discussed by Tobias and Schubert' in 1959 when they attempted to estimate its size in a study of binaural function. They thought that, for stimuli shorter than the onset-duration, changes in waveform should not be perceptible. Although unable to predict a precise value, they did estimate a maximum limit of about 3 ms. To calculate the 3 ms, they assumed that duration was the sole contributor to the weighting of any stimulus segment, although several other onset-weighting factors must have been involved (primary among these being the well-known on-effece and the effect of time-since-onset on "binaural memory" ). However, these factors could not be taken into account because of limitations in the available data. 1 Tobias, J. V., and E. D. Schubert. "Effective OnsetDuration of Auditory Stimuli," ]. Acoust. Soc. Am. 31, 1595-1605 ( 1959). 1 Derbyshire, A. J., and H. Davis. "The Action Potentials of the Auditory Nerve," Am. ]. Physiol. 113, 476-504 ( 1935). The next step involves finding the onsetduration directly rather than in the indirect and somewhat cumbersome fashion used by Tobias and Schubert. Several techniques some monaural, some binaural are possible. For instance, differentially filtered noise bursts of varying duration might be compared, but there is a strong possibility that short bursts would ring the filter for too long to allow proper control of duration. The use of any filter therefore seems inadvisable in this sort of work. (Indeed, if the onset-duration concept is correct, the perception of "sharp" and "dull"that is, high and low pitched clicks results from overly long acoustic stimulation, since any truly short click should sound like any other on the sharp-dull continuum.) A more defensible approach, and the first one used in this study, requires a binaural analysis of the stimulus: two binaural conditions are compared at a number of stimulus durations. 3 Tobias, J. V., and S. Zerlin. "La'teralization Threshold as a Function of Stimulus Duration,"]. Acoust. Soc. Am. 31, 1591-1594 ( 1959) 0 0 The work reported here was performed at the Defense Research Laboratory of the University of Texas while the senior author was employed there as Research Scientist in the Undersea Warfare and Acoustics divisions. The paper has been published in The Journal of the Acoustical Society of America 34, 857-858 ( 1962).