48,177 research outputs found
Virtual pitch integration for asynchronous harmonics
This experiment examined the generation of virtual pitch for harmonically related tones that do not overlap in time. The interval between successive tones was systematically varied in order to gauge the integration period for virtual pitch. A pitch discrimination task was employed, and both harmonic and nonharmonic tone series were tested. The results confirmed that a virtual pitch can be generated by a series of brief, harmonically related tones that are separated in time. Robust virtual pitch information can be derived for intervals between successive 40-ms tones of up to about 45 ms, consistent with a minimum estimate of integration period of about 210 ms. Beyond intertone intervals of 45 ms, performance becomes more variable and approaches an upper limit where discrimination of tone sequences can be undertaken on the basis of the individual frequency components. The individual differences observed in this experiment suggest that the ability to derive a salient virtual pitch varies across listeners
Virtual Reality and Sound Localization
Psychoacoustics is the scientific study of sound perception. Within this field, Virtual Reality is a technique that uses two synthesis speakers to simulate a sine tone coming from anywhere in open space. Using this method it is possible to independently control specific binaural cues in a free-field environment. This study analyzes listener responses to these controlled sine tones to investigate the relative importance of certain binaural cues at different frequencies
Three-Dimensional (3D) Audio Laser for Virtual Reality Systems
A three-dimensional (3D) audio laser for VR systems is provided. The 3D audio laser is a system that includes a laser pointer and a dedicated audio location control. The system uses sound to orient a user to a virtual object and to provide an audible description of the virtual object. A location and a name (or other description) of virtual objects in the VR environment are known to the VR system. When the user aims the laser pointer at a particular virtual object and selects the dedicated audio location control, the VR system plays a series of tones with simulated locations at specified distances between the user and the virtual object. The distances are known to the user (e.g., given in the user manual for the VR system). After the series of tones is played, the name or description of the virtual object is played. The user can thereby discover the name and location of the virtual object, even if it the user cannot visually determine them
Different Modes of Pitch Perception and Learning-Induced Neuronal Plasticity of the Human Auditory Cortex
We designed a melody perception experiment
involving eight harmonic complex tones of
missing fundamental frequencies (hidden auditory
object) to study the short-term neuronal plasticity
of the auditory cortex. In this experiment, the
fundamental frequencies of the complex tones
followed the beginning of the virtual melody of
the tune “Frère Jacques”. The harmonics of the
complex tones were chosen so that the spectral
melody had an inverse contour when compared
with the virtual one. Evoked magnetic fields were
recorded contralaterally to the ear of stimulation
from both hemispheres. After a base line measurement,
the subjects were exposed repeatedly to the
experimental stimuli for 1 hour a day. All subjects
reported a sudden change in the perceived melody,
indicating possible reorganization of the cortical
processes involved in the virtual pitch formation.
After this switch in perception, a second measurement
was performed. Cortical sources of the
evoked gamma-band activity were significantly
stronger and located more medially after a switch
in perception. Independent Component Analysis
revealed enhanced synchronization in the gamma-band
frequency range. Comparing the gamma-band
activation of both hemispheres, no
laterality effects were observed. The results
indicate that the primary auditory cortices are
involved in the process of virtual pitch
perception and that their function is modifiable
by laboratory manipulation
Virtual Pitch and Pitch Shifts in Church Bells
It is well established that musical sounds comprising multiple partials with frequencies approximately in the ratio of small integers give rise to a strong sensation of pitch even if the lowest or fundamental partial is missing—the so-called virtual pitch effect. Experiments on thirty test subjects demonstrate that this virtual pitch is shifted significantly by changes in the spacing of the constituent partials. The experiments measured pitch by comparison of sounds of similar timbre and were automated so that they could be performed remotely across the Internet. Analysis of the test sounds used shows that the pitch shifts are not predicted by Terhardt’s classic model of virtual pitch. The test sounds used were modelled on the sounds of church bells, but a further experiment on seventeen test subjects showed that changes in partial amplitude only had a minor effect on the pitch shifts observed, and that a pitch shift was still observed when two of the lowest frequency partials were removed, so that the effects reported are of general interest
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Metrics for pitch collections
Models of the perceived distance between pairs of pitch collections are a core component of broader models of the perception of tonality as a whole. Numerous different distance measures have been proposed, including voice-leading, psychoacoustic, and pitch and interval class distances; but, so far, there has been no attempt to bind these different measures into a single mathematical framework, nor to incorporate the uncertain or probabilistic nature of pitch perception (whereby tones with similar frequencies may, or may not, be heard as having the same pitch).
To achieve these aims, we embed pitch collections in novel multi-way expectation arrays, and show how metrics between such arrays can model the perceived dissimilarity of the pitch collections they embed. By modeling the uncertainties of human pitch perception, expectation arrays indicate the expected number of tones, ordered pairs of tones, ordered triples of tones and so forth, that are heard as having any given pitch, dyad of pitches, triad of pitches, and so forth. The pitches can be either absolute or relative (in which case the arrays are invariant with respect to transposition).
We provide a number of examples that show how the metrics accord well with musical intuition, and suggest some ways in which this work may be developed
Hex Player—a virtual musical controller
In this paper, we describe a playable musical interface for tablets and multi-touch tables. The interface is a generalized keyboard, inspired by the Thummer, and consists of an array of virtual buttons. On a generalized keyboard, any given interval always has the same shape (and therefore fingering); furthermore, the fingering is consistent over a broad range of tunings. Compared to a physical generalized keyboard, a virtual version has some advantages—notably, that the spatial location of the buttons can be transformed by shears and rotations, and their colouring can be changed to reflect their musical function in different scales.
We exploit these flexibilities to facilitate the playing not just of conventional Western scales but also a wide variety of microtonal generalized diatonic scales known as moment of symmetry, or well-formed, scales. A user can choose such a scale, and the buttons are automatically arranged so their spatial height corresponds to their pitch, and buttons an octave apart are always vertically above each other. Furthermore, the most numerous scale steps run along rows, while buttons within the scale are light-coloured, and those outside are dark or removed.
These features can aid beginners; for example, the chosen scale might be the diatonic, in which case the piano’s familiar white and black colouring of the seven diatonic and five chromatic notes is used, but only one scale fingering need ever be learned (unlike a piano where every key needs a different fingering). Alternatively, it can assist advanced composers and musicians seeking to explore the universe of unfamiliar microtonal scales
Neural Correlates of Auditory Perceptual Awareness and Release from Informational Masking Recorded Directly from Human Cortex: A Case Study.
In complex acoustic environments, even salient supra-threshold sounds sometimes go unperceived, a phenomenon known as informational masking. The neural basis of informational masking (and its release) has not been well-characterized, particularly outside auditory cortex. We combined electrocorticography in a neurosurgical patient undergoing invasive epilepsy monitoring with trial-by-trial perceptual reports of isochronous target-tone streams embedded in random multi-tone maskers. Awareness of such masker-embedded target streams was associated with a focal negativity between 100 and 200 ms and high-gamma activity (HGA) between 50 and 250 ms (both in auditory cortex on the posterolateral superior temporal gyrus) as well as a broad P3b-like potential (between ~300 and 600 ms) with generators in ventrolateral frontal and lateral temporal cortex. Unperceived target tones elicited drastically reduced versions of such responses, if at all. While it remains unclear whether these responses reflect conscious perception, itself, as opposed to pre- or post-perceptual processing, the results suggest that conscious perception of target sounds in complex listening environments may engage diverse neural mechanisms in distributed brain areas
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