Eliminating subjective biases in judging the loudness of a 1-kHz tone

It is possible to eliminate most of the known subjective biases that affect judgments of sensory magnitude using numbers. Experiments are described which do this, and which also investigate some of the biases. The least biased estimate for doubling the loudness of a 1-kHz tone is found to be about 11.5 dB. This value is still slightly affected by the logarithmic bias, although the bias could be eliminated. It is also affected by the stimulus equalizing bias, produced by the inequality between the finite range of loudnesses to which the ears are sensitive and the infinite range of numbers to which the loudnesses are matched. This last bias cannot be eliminated completely in direct magnitude estimation.     

Induced loudness reduction as a function of frequency difference between test tone and inducer

When a high-intensity tone (inducer) is followed by a moderate-intensity tone (test tone), the loudness of the latter is reduced. This phenomenon, called induced loudness reduction (ILR), depends on the frequency separation of the two tones; as the difference in frequency increases, the amount of ILR decreases. However, the precise course of this decrease is not well known. This article presents two experiments that address this question. In the first experiment, the amount of loudness reduction produced by a 2.5-kHz 80-dB-SPL inducer was measured with the frequency of the test tone swept from 800 Hz to 6 kHz. In the second experiment, the amount of ILR was measured with the same inducer and with test tones set at 2, 2.5, 3, and 4 kHz. Both experiments show that some ILR occurs at frequency separations as wide as four critical bands.     

Brighter noise: Sensory enhancement of perceived loudness by concurrent visual stimulation

Two experiments investigated the effect of concurrently presented light on the perceived loudness of a low-level burst of white noise. The results suggest two points. First, white noise presented with light tends to be rated as louder than noise presented alone. Second, the enhancement in loudness judgments is resistant to two experimental manipulations: varying the probability that light accompanies sound and shifting from a rating method to a forced choice comparison. Both manipulations were previously shown to eliminate a complementary noise-induced enhancement in ratings of brightness. Whereas noise-induced enhancement of brightness seems to reflect a late-stage decisional process, such as a response bias, the present results suggest that light-induced enhancement of loudness may reflect an early-stage sensory interaction.     

The slow formation of a pitch percept beyond the ending time of a short tone burst

The discriminability of short tone bursts differing in frequency was measured in terms of the sensitivity index d' as a function of interstimulus interval (ISI). The two stimuli presented on each trial consisted of either 6 or 30 sinusoidal cycles. When the frequency of the first stimulus varied randomly and widely from trial to trial (Experiment 1), discriminability was maximal for an ISI of about 400 msec in the 6-cycles condition and for a significantly longer ISI (of about 1 sec) in the 30-cycles condition. However, when the first stimulus had only two possible frequencies and the second stimulus was fixed (Experiment 2), the optimal ISI appeared to be about 400 msec in both conditions. A final experiment confirmed that, for tone bursts of 30 cycles, the optimal ISI was dependent on the perceptual uncertainty of the first stimulus. These results support the idea that the duration required to perceive the pitch of a sound as accurately as possible may far exceed the duration of the stimulus itself. More importantly, they indicate that the required duration is not a constant.     

Effects of expectations on loudness and loudness difference

To determine how expectations affect loudness and loudness difference, in two experiments we induced some subjects to expect loud sounds (condition L), some to expect soft sounds (condition S), and others to have no particular expectations (control). In Experiment 1, all subjects estimated the loudnesses of the same set of three moderately loud 1-kHz tones. Estimates were greatest for subjects in condition S and smallest for subjects in condition L. Control subjects’ estimates were intermediate but closer to those of condition S subjects. In Experiment 2, subjects estimated the difference in loudness for pairs of moderately loud 1-kHz tones. Again, estimates were smallest for condition L subjects; estimates were greatest for control subjects, and condition S subjects’ estimates were closer to control estimates than to condition L estimates. This pattern of results is explainable by a combination of (1) Parducci’s (1995) range-frequency theory and (2) a gain control mechanism in the auditory system under top-down governance (Schneider, Parker, & Murphy, 2011).     

The enhancement of hippocampal primed burst potentiation by dehydroepiandrosterone sulfate (DHEAS) is blocked by psychological stress

This series of studies investigated the effects of psychological stress and the neurosteroid dehydroepiandrosterone sulfate (DHEAS) on hippocampal primed burst (PB) and long-term (LTP) potentiation, two electrophysiological models of memory. The DHEAS and stress manipulations were performed on awake rats, and then PB and LTP were recorded while the rats were anesthetized. DHEAS enhanced PB potentiation when administered to rats under non-stress conditions, but had no effect when given to stressed rats. Further study showed that DHEAS enhanced PB potentiation only when it was administered before, but not after, the rats were stressed. The DHEAS and stress manipulations had no effect on LTP. This study provides three major findings regarding stress, neurosteroids and hippocampal plasticity. First, DHEAS enhanced a threshold form of plasticity (PB potentiation), but had no effect on a supra-threshold form of plasticity (LTP). Second, stress blocked the DHEAS-induced enhancement of PB potentiation. Third, stress and DHEAS effects on the hippocampus were so durable they could be performed on awake animals and then be studied while the animals were anesthetized. That DHEAS enhanced a subset of forms of hippocampal plasticity under restricted behavioral conditions may help to resolve conflicting observations of DHEAS effects on cognition and mood in people.     

Bisection of loudness

In a loudness bisection task, subjects varied one sound to lie halfway between two given sounds in terms of loudness. The two given sounds were varied from 30 to 90 dB in a 4 by 9 factorial design. Functional measurement methods based on monotone analysis provided good support for the bisection model, and yielded a loudness scale with an exponent of about .3, except for a falloff at lower intensities. Two other tasks, judging average loudness and difference in loudness of the two given sounds, yielded mixed results. In Experiment 2, in particular, the differencing judgments were not additive, even under monotone transformation. These analyses also indicated that previous applications of monotone analysis have typically lacked adequate power to allow any conclusion about the operative model. Overall, the present bisection scale agrees with Garner’s lambda scale, and the present theoretical approach agrees with that of Garner in its emphasis on algebraic models as a foundation for psychological measurement.     

Shortening of subjective tone intervals followed by repetitive tone stimuli

Accumulated evidence shows that a subjective time interval is lengthened by preceding or concurrent presentation of flickers or repetitive tone stimuli that have been hypothesized to increase the frequency of pulse generation by a brain pacemaker. In the present study, we presented a series of repetitive tone stimuli after an interval that started and ended with tone markers. We found that subjective perception of the preceding interval was not lengthened but shortened by the tone stimuli that followed the interval. The perceived duration decreased as the frequency of the repetitive tone stimuli increased. The effect disappeared when the repetitive tone stimuli were delivered with a delay of 500 msec after the test interval or when continuous sound was delivered instead of delivering a rapid series of tones. On the basis of the results, we propose that the pulse count accumulated during a test interval was normalized by the clock frequency just after the test interval in a postdictive manner.     

Range and regression, loudness scales, and loudness processing: toward a context-bound psychophysics

How does context affect basic processes of sensory integration and the implicit psychophysical scales that underlie those processes? Five experiments examined how stimulus range and response regression determine characteristics of (a) psychophysical scales for loudness and (b) 3 kinds of intensity summation: binaural loudness summation, summation of loudness between tones widely spaced in frequency, and temporal loudness summation. Context affected the overt loudness scales in that smaller power-function exponents characterized larger versus smaller range of stimulation and characterized magnitude estimation versus magnitude production. More important, however, context simultaneously affected the degree of loudness integration as measured in terms of matching stimulus levels. Thus, stimulus range and scaling procedure influence not only overt response scales, but measures of underlying intensity processing.     

Individual loudness functions determined from direct comparisons of loudness intervals

Five subjects were required in each trial to directly compare two pairs of tones and indicate which pair of tones had the greater loudness difference. Ten 1,200-Hz tones differing only in intensity were employed. Subjects made binary comparisons among the 45 tone pairs that can be formed from these 10 tones. The loudness difference comparisons of each subject were found to satisfy two properties (transitivity and monotonicity) that are required for an interval scale representation of loudness. Therefore, individual loudness scales were constructed using a nonmetric scaling technique designed for comparisons of sensory intervals. These loudness scales differed significantly from subject to subject. Since a nonnumerical scaling procedure was employed, these individual differences could not be attributed to biases in the way in which observers use numbers or numerical concepts to describe the loudness of tones. Hence, they suggest strong individual differences in the coding of sound intensity.     

Binaural loudness gain measured by simple reaction time

In order to yield equal loudness, different studies using scaling or matching methods have found binaural level differences between monaural and diotic presentations ranging from less than 2 dB to as much as 10 dB. In the present study, a reaction time methodology was employed to measure the binaural level difference producing equal reaction time (BLDERT). Participants had to respond to the onset of 1-kHz pure tones with sound pressure levels ranging from 45 to 85 dB, and being presented to the right, the left, or both ears. Equal RTs for monaural and diotic presentation (BLDERTs) were obtained with a level difference of approximately 5 dB. A second experiment showed that different results obtained for the left and right ear are largely due to the responding hand, with ipsilateral responses being faster than contralateral ones. A third experiment investigated the BLDERT for dichotic stimuli, tracing the transition between binaural and monaural stimulation. The results of all three RT experiments are consistent with current models of binaural loudness and contradict earlier claims of perfect binaural summation.     

Cross-modality matching of brightness to loudness by 5-year-olds

The purpose was to determine whether 5-year-old children could match the brightness of a light to the loudness of a sound, and whether the resulting cross-modality function resembled the power function produced by adults. Each of five children adjusted the voltage on a 15D-W lamp to make the apparent brightness appear equal to the loudness of a 500-Hz tone, which the E set to eight different levels. The results resembled those of five adults who performed the same task.     

The cross-modal matching of brightness to loudness by children

According to Stevens' explanation of cross-modal matching, the recruitment-like effects of masking seen in intramodal loudness judgements should be reflected in a brightness-to-loudness matching task. In an experiment with child observers, this failed to occur. The results are explicable in terms of category mediation of the cross-modal, but not the intramodal, task. In support of this account, it is shown that cross-modal judgements are unaffected by explicit category mediation. However, intramodal judgements, explicitly mediated in the same way, produce a pattern of results similar to those obtained in the cross-modal task. The experiments suggest that cross-modal matching does not provide a useful test of loudness recruitment in the bilaterally hearing impaired.     

Discrimination of loudness similarity

Interval and ratio scale values were derived from measures of variability in the discrimination of loudness similarity. The interval values are linearly related to interval values based on equisection judgments (Garner, 1954), cumulating jnds (Riesz, 1933), and the dispersion of absolute judgments (Gamer, 1952). Scale values based on three diverse discriminability procedures and on the method of equisection are thus in good agreement. The ratio lvalues, however, are at variance with ratio values determined by direct ratio estimations (Stevens, 1955).