RELATION OF EARPHONE TRANSIENT RESPONSE 

TO MEASUREMENT OF ONSET-DURATION 

JERRY V. TOBIAS, Ph. D. 

Sensory Psychology Section 

PSYCHOLOGY BRANCH 

LLOYD A. JEFFRESS, Ph. D. 

Research Scientist 

'DEFENSE RESEARCH LABORATORY 

and Professor 

DEPARTMENT OF PSYCHOLOGY 

THE UNIVERSITY OF TEXAS 

63-7 

FEDERAL AVIATION AGENCY 

AVIATION MEDICAL SERVICE 

AEROMEDICAL RESEARCH DIVISION 

CIVIL AEROMEDICAL RESEARCH INSTITUTE 

OKLAHOMA CITY, OKLAHOMA 

MARCH 1963 

• 

RELATION OF EARPHONE TRANSffiNT RESPONSE TO 

MEASUREMENT OF ONSET-DURATION° 

JERRY V. TOBIAS, Ph. D. 

LLOID A. JEFFRESS, Ph.D. 

ABSTRACT 

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 short- or 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"3

). 

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). 

-1-
EXPERIMENTS 

It was postulated that subjects would make 

almost 100 percent correct differentiations 

between interaural correlation conditions' of 

+ 1 and 0 for long noise bursts and chance 

differentiations for short bursts. The division 

between long and short must be the onsetduration. However, judgments were 100 percent correct for any noise-burst length. Phenomenologically, the + 1 correlation stimuli 

were of course in the median plane; 0 correlation stimuli varied in azimuth, probably because of the random interaural time difference 

in onset. Judgments were necessarily easy on 

the basis of the localization. 

In the second approach, the troublesome 0 

correlation condition was not used; a -I condition was substituted. . Since only the rarefaction half-cycle of the waveform actually serves 

as a stimulus,' some "jumping" of the perceived image (as occurred with 0 correlation) 

was expected, but instead only the commonly 

reported separation to the two earphones was 

noted for the -1 stimuli. Here too, judgments 

were 100 percent correct at any burst length. 

However, these apparently negative results 

can be used to modify the original onsetduration estimate if some use is made of transducer response. If one assumes that an onsetduration exists and that it is of the order of 

1-3 ms, it becomes obvious that the signal must 

not have been adequately specified for the 

shorter durations. The clear cause of the inadequacy is poor transient response of the earphones. Specification of the stimulus duration 

below which the phones refused to behave, then, 

should give a new upper limit for onsetduration. 

The procedure was simple: oscilloscope trace 

photographs were made of PDR-8 earphone 

responses to two kinds of transient signals, 

rectangular current pulses and short noise bursts 

("short" ranging from 0.09 to 10 ms). The 

phones were the ones used in the listening 

' Licklider, J. C. R. "The Influence of Interaural 

Phase Relations upon the Masking of Speech by White 

Noise," ]. Acoust. Soc. Am. 20, 150-159 ( 1948). 

• Tasaki, I. "Nerve Impulses in the Individual Auditory 

Nerve Fibers of Guinea Pig,"]. Neurophysiol. 17, 97-122 

( 1954); and H. Davis. "Biophysics and Physiology of 

the Inner Ear," Physiol. Rev. 37, 1-49 ( 1957). 

experiments although other phones were tried 

with similar results. Figure 1 shows the response of a phone to several lengths of rectangular pulse: 2, 1, 0.5, and 0.1 ms. At 1 and 

J[_ 

......__. 

0 .$ lffiMC .r-:t-1--

RESPONSE OF PDR -e's TO RECTANGULAR PULSE 

RESPONSE OF PDR-8'5 TO RECTANGULAR PULSE 

FIGURE 1. Response of PDR-8 earphone to 0.1-, 0.5-, 1.0., 

and 2.0-rns rectangular current pulses. 

2 ms, the acoustic pattern was the characteristic 

symmetrical double response - positive following the initial transient, negative after the release. The form of the response was the same 

for both pulse lengths. For 0.5 ms, the phone 

started to produce the same output but was 

unable to complete the first response before the 

second half started. The very early second half 

in the 0.1-ms case produced a waveform that 

looks quite different from any of the others. 

-2-
In aU cases, the acoustic duration was well 

over a millisecond, and the shortest possible 

duration (found by measuring the positive part 

of the 1 or 2 ms waves) is at least 0.8 ms. Thus, 

even if the signal were an infinitesimally short 

transient, these phones would respond for nearly 

a millisecond. 

The possibility that noise bursts might behave differently led to similar measurements on 

gated noise inputs. Figure 2 shows some typical 

results for noise bursts of 2, 1, 0.5, and 0.1 ms, 

switched with very short rise and decay times. 

The 2-ms samples varied from one another 

much as should be expected for random input, 

and the acoustic duration, exclusive of the 8-kc 

ringing, was 2 ms. The 1-ms samples were similar except for their duration which was perhaps 

1/2 ms more than the 1 ms of electrical activity. 

Each of the 0.5-ms bursts actually extended 

beyond a millisecond acoustically, and the 

0.1-ms bursts produced activity for 0.7-0.8 ms. 

In this last case, the phone seemed to behave 

almost as if it had been hit by short rectangular pulses of varying amplitude, which is 

what would be predicted. 

CONCLUSIONS 

It is now necessary to derive some information from these waveforms to allow a revision 

of the onset-duration estimate. First, it is worth 

noting that the contribution of the phone to 

the stimulus becomes relatively large for inputs 

of perhaps 1.5-ms duration or less. But the 

datum which is directly useful is the length 

(0.7-0.8 ms) of the click-like sound produced 

by very short noise bursts. In the situation-in 

which stimuli are either interaurally in-phase 

short bursts or 180° out-of-phase short bursts, 

subjects can differentiate perfectly between the 

two conditions. Thus, the onset-duration if it 

exists must lie below 0.8 ms. 

One further point deserves restatement. Since 

psychophysical experiments of this sort are designed, in effect, to discover interaural correlation problems which cannot be solved in any 

fashion by the binaural system, it is necessary 

to conclude that transduction by standard earphones cannot be used. Matched phones will 

-.......... 

0 .5 lfRMC 

RESPONSE OF PDR-8'S TO RAfoiDOM IIIOISE 

RESPONSE Of PDR -a'S TO RAfoiDOM I'IOISE 

FIGURE 2. Typical responses of PDR-8 earphone to 0.1-, 

0.5-, 1.1-, and 2.0-ms rectangular bursts of noise. 

simply add similarity to the stimuli at the two 

ears no matter what the electrical input may be. 

The more closely the phones are matched, and 

the shorter the duration of the electrical activity, the worse the problem becomes. Attempts 

to produce dichotic or incoherent short-duration 

stirimli are doomed to be confounded by the 

interaural similarities forced upon the stimulus 

by standard transducers. 

-3- U. S. GOVERNMENT PRINTING OFFICE : 1963 0 - 694-208