Loudness scaling and masking in rats.

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In Experiment 1, rats discriminated between two sound pressure levels (SPL) of a pure tone: standard (STD) SPLs of 84 and 74 dB and comparison (CO) SPLs 4, 14, and 24 dB below STD were tested in quiet and 60 dB noise at 4 and 12.5 kHz (24 conditions). The decibel difference between STD and CO accounted for only 43.52% of the variance in the signal detection measure of sensitivity, d', across conditions, whereas the loudness difference (LD = STD0.35 - CO0.35) accounted for 89.82% of the variance in d'. These results confirm and extend previous observations that: (a) equal decibel differences are not equally discriminable; (b) loudness for the rat increases as a power function of SPL with an exponent of 0.35: and (c) masked loudness is a linear function of loudness in quiet. In Experiment 2, the assumptions of normal distribution and equal variance implicit in the use of the d' measure were examined. Receiver operating characteristic curves that were well approximated by straight lines of unit slope in normal-normal coordinates were obtained and thereby validated the use of d' in Experiment 1.

Section: Resultssupporting

confidence: 90%

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confidence: 95%

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confidence: 99%

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confidence: 99%

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Discriminability, loudness, and masking in the rat (Rattus norvegicus): A confirmation and extension.

Raslear¹

1989

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“…An additional purpose of the research was to reexamine the effects of masking noise on loudness. With discriminability methods, it was previously demonstrated that masking noise decreases the discriminability of pure tonal auditory intensities and that pairs of stimulus intensities that are equally discriminable in quiet remain equally discriminate in noise (Raslear et al, 1983). This implies that masked loudness is a linear function of loudness in quiet (Raslear et al, 1983):…”

Section: B) =mentioning

confidence: 99%

Loudness bisection and masking in the rat (Rattus norvegicus).

Raslear¹,

Shurtleff²,

Simmons³

1992

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The bisection method of animal psychophysical scaling was examined as a measurement procedure. The critical assumptions of bisection scaling, as described by Pfanzagl (1968), were tested to determine if a valid equal-interval scale could be derived. A valid scale was derived in which loudness for the rat (Rattus norvegicus; n = 13) was a power function of sound pressure for 4-kHz tones. Masking noise reduced the discriminability of tonal stimuli but did not affect the bisection point. This result is consistent with an interval scale representation of loudness and demonstrates scale meaningfulness. Loudness bisection data that have been reported in the literature for 3 species (humans, rats, and pigeons) are in substantial agreement with our results.

Perceptual organization of acoustic stimuli by budgerigars (Melopsittacus undulatus): I. Pure tones.

Dooling

Brown²,

Park³

et al. 1987

A new combination of operant conditioning and psychophysical scaling procedures was used to study auditory perception in a small bird. In a same-different discrimination task, budgerigars learned to discriminate among pure tones that varied along one or more acoustic dimensions. Response latencies were used to generate a matrix of interstimulus similarities. Multidimensional scaling procedures were used to arrange these acoustic stimuli in a multidimensional space that supposedly reflects the bird's perceptual organization. For tones that varied in intensity, duration, and frequency simultaneously, budgerigars were much more sensitive to frequency changes. From a set of tones that varied only in intensity, it was possible to calculate the growth of loudness with intensity for the budgerigar. For tones that varied only in frequency, budgerigars showed evidence of an "acoustic fovea" for frequency change in the spectral region of 2-4 kHz. Budgerigars and humans also differed in their perceptual grouping of tone sequences that rise, fall, or remain constant in pitch. Surprisingly, budgerigars were much less responsive to pitch contour than were humans. This work was supported by National Institutes of Health Grants NS19006 and HD00512 to Robert J. Dooling. We thank S. Brauth and M. Penner for comments on an earlier draft and Brian Dooling for care of the birds.