Pitch Of Pure Tones Research Articles

The effect of band-limited noise on the pitch of pure tones

An investigation has been made of the effect of a band of noise, one-third of an octave wide, on the perceived pitch of a pure tone. In general, the pitch was found to “move away” from the interfering noise. However, in contrast with the results of earlier workers, the shifts in pitch were found to be quite small and it is suggested that this may be due to the differences in experimental procedures.

Diplacusis and Auditory Theory

Following exposure to a series of high-intensity pulses that produced a marked auditory fatigue at 1000 cps and above, significant tonal binaural diplacusis was found to exist at even lower frequencies. The mean shift, for 6 listeners, in the frequency of a tone in the fatigued ear required to match the pitch of a fixed tone in the unexposed ear, was 6.5% at 500 cps, 4.5% at 200 cps, 2.5% at 150 cps, and zero at 100 cps. It is concluded that the perception of the pitch of pure tones can be mediated by the frequency of neural discharge only when the tonal frequency is 100 cps or lower.

Further Investigation of the Effects of Intensity upon the Pitch of Pure Tones

Typical methods for observing pitch changes with intensity for pure tones consist of varying the frequency of one tone of fixed intensity (the comparison tone) so as to match the pitch of a second tone of fixed frequency (the tone under test) when the latter is set at different intensities. Differences between the comparison and test-tone frequencies, when equated in pitch under these conditions, are ascribed to their intensity differences and used as a measure of the pitch intensity shifts for the test tone. The comparison and test tones may differ in frequency, however, even when they are matched in pitch under equal intensity conditions. These frequency differences, called pitch-matching errors, may be identical to those noted above for comparable conditions and consequently nullify the apparent pitch-intensity shifts. This possibility was studied in two experiments which sought to reproduce the pitch intensity relationship as defined by the data of Stevens and Snow. In more than half the comparisons made under various frequency and intensity conditions, apparent pitch shifts for 50, 75, 100, 200, 400, 700, 1500, and 6000 cps were found to be not significantly different from pitch-matching errors. When averaged, the remaining shifts followed the directions of Stevens' curves but were small (2% or less). Pitch-intensity functions for the lower frequency tones were particularly variable and generally bore little relationship to Snow's functions for such tones.

Further Assessment of the Effects of Intensity upon the Pitch of Pure Tones

Typical methods for observing the effects of intensity upon the pitch of pure tones involve varying the frequency of one tone of fixed intensity (the comparison tone) so as to match the pitch of a second tone of fixed frequency (the tone under test) as the latter is set at different intensities. Differences between the frequency of the comparison and test-tones, when equated in pitch under these conditions, are attributed to their differences in intensity. These differences are used as a measure of the intensity induced pitch shift for the test tone. The comparison and test tones may differ in frequency, however, even when both tones are equated in pitch under equal intensity conditions. These frequency differences, reflective of pitch matching errors, conceivably may vary for different frequencies and intensities so as to nullify apparent pitch-intensity shifts or qualify the magnitude of those being observed. This possibility was studied in two experiments which were intended to reproduce Stevens' pitch-intensity relationship as well as explore new functions for tones of particularly low frequency, It was found that half of the “pitch-intensity” shifts noted for frequencies 50, 75, 100, 150, 200, 400, 700, 1500, and 6000 cps were not significantly different from pitch matching errors. The remaining shifts were in directions reported by Stevens but were typically small (2% or less). The lowest frequency tone to show a significant pitch change was 75 cps.

Human Skin Perception of Traveling Waves Similar to Those on the Cochlea

The membrane of a dimensional model of the mechanical parts of the human cochlea (30 cm in over-all length) showed under stroboscopic illumination traveling waves similar to those on the cochlea and a flat maximum of vibration which shifted from one end of the model to the other when the frequency was increased from 40 cps to 160 cps. When the skin of the arm is placed in close contact with the membrane, the vibrations are localized in a quite narrow section of the membrane, so that any change in frequency can be detected by a change in the locus of stimulation. The localization is as sharply defined for pure tone pulses of the length of two sine waves as for continuous tones. The localization of pure tones along the membrane is practically instantaneous. The sharp localization in spite of the flat distribution of vibrations along the membrane is produced by the inhibitory effects of the skin. Their influence and magnitude are demonstrated by various experiments. Some basic relations between nerve density on the cortex, threshold, and loudness increase on the skin are pointed out in the hope that they will later enable us to determine the differences between the organ of Corti and the simple skin membrane. This would be helpful to our understanding of the nature and function of the complicated structure of the organ of Corti. On the whole, in the observation of pitch of pure tones, the simple skin-model is as useful as the organ of Corti itself. The differences become apparent only in the observation of more complex sounds. Two models were used to investigate the possibility of obtaining effects similar to the stereophonic effects in hearing.

Historical Note on Thermal Masking Noise and Pure Tone Pitch Changes

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Changes in Pitch of Tones of Low Frequency as a Function of the Pattern of Excitation Produced by a Band of Noise

The excitation pattern of a tone is markedly altered by a masking stimulus. It should be expected that the pitch of the masked tone, as well as its threshold and its loudness, would be affected. In the present investigation the effect of a narrow band of noise (90 c.p.s. wide, centered at 410 c.p.s.) upon the pitch of pure tones of low frequency was measured in a series of experiments. Subjects matched the pitch of a tone heard in the presence of a band of noise to the pitch of a tone heard alone. These two tones, one partially masked and the other not, were presented to the subject in repeated succession. The listener first matched these tones for loudness. He then adjusted the frequency of the unmasked tone until it was the same in pitch as the masked tone. The pitch change was investigated at a number of frequencies and of loudness levels. Systematic changes in pitch were observed. The presence of the noise raises the pitch of a partially masked tone whose frequency is immediately above those of the band of noise. This change in pitch occurs even though the intensity of the masked tone is greater than that of the unmasked tone. In contrast, the presence of the masking noise lowers the pitch of a tone whose frequency is just lower than those of the band of noise, but this change is largely accounted for in terms of the intensity difference required for an equal loudness match. An attempt is made to account for the changes in pitch in terms of a place theory.

Rise in Pitch of Pure Tone on Introduction of Thermal Noise

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The Reactions of Infants to Changes in the Intensity and Pitch of Pure Tone

Abstract * Recommended for publication by John J. B. Morgan, accepted by Carl Murchison of the Editorial Board, and received in the Editorial Office, February 27, 1931. 1 Report of an experiment conducted in the Psychological Laboratory of Northwestern University. The work was done under the direction of Professor John J. B. Morgan.