The Cone of Confusion: High Pitched Pure Sine Wave Tones have no three dimensional "edge" for brain phase difference perceptions

 Interaural time difference and how to find your phone instantly

 trigonometriphiles will find an equation showing that the sum of two sine waves of the same frequency is always another sine of the same frequency, albeit with a different amplitude and phase. The equation even tells exactly what the amplitude and phase of the resulting wave are in terms of the phase difference of the original waves. These equations also describe (in part) the perceptual reality of combining sine waves in sound. Constructive interference reflects the common sense idea that two sine waves are louder than one. Destructive interference can be used to cancel (or muffle)noises by injecting sine waves of the same frequencies as the noises but with different phases, thus canceling out the unwanted sound.

Sound on Sound 

The two primary theories of peripheral pitch coding involve stimulus-driven spike timing, or phase locking, in the auditory nerve (time code), and the spatial distribution of responses along the length of the cochlear partition (place code). To rule out the use of timing information, we tested pitch discrimination of very high-frequency tones (>8 kHz), well beyond the putative limit of phase locking. We found that high-frequency pure-tone discrimination was poor, but when the tones were combined into a harmonic complex, a dramatic improvement in discrimination ability was observed that exceeded performance predicted by the optimal integration of peripheral information from each of the component frequencies. The results are consistent with the existence of pitch-sensitive neurons that rely only on place-based information from multiple harmonically related components. The results also provide evidence against the common assumption that poor high-frequency pure-tone pitch perception is the result of peripheral neural-coding constraints. The finding that place-based spectral coding is sufficient to elicit complex pitch at high frequencies has important implications...

https://www.sciencedirect.com/science/article/pii/S0378595518305604 

 In all cases, the perceived pitch corresponds approximately to the reciprocal of the most prominent interval.

 Because of our auditory system's exquisite temporal sensitivity, differences between the arrival of sound at one ear and its arrival at the other ear can be detected down to tens of microseconds.

Ultrasound Frequency!!

 Finally, a long-standing impediment to accepting phase locking to TFS as a viable method for processing monaural frequency information is the lack of any physiological candidates to carry out the computation.

 dogma in the field has been that phase-locking information exists (and may be used) up to ∼4000 Hz, but above 4000 Hz no temporal information exists and thus rate-place information is used. The approach presented here quantitatively integrates data from animal and human studies via computational modeling to suggest that this dogma is not correct, and to provide evidence suggesting that humans can in fact (and in at least some cases do) use phase-locking information at much higher frequencies than is commonly believed.

 

Direct evidence pinning down the physiological UL-FS [Upper Frequency Limit] would require recordings from the human CNS, but then relating such recordings to perception is not a trivial manner.

 Shamma suggests that information regarding the upper limit may also be obtained by studying the electrical properties of human inner hair cells in vitro.