of Dec 2023, 23:12
This year was particularly fruitful when it comes to publications. Having a lot of research piling up on my back catalogue, I was finally able to get some of it past peer review, out there in the wild, for the public to read and judge.
First, I was able to present our research on circularly moving sources at the AES convention in Helsinki Finland in Spring. Here, we mainly focused on the physical phenomena of measuring a sound source emitting a pure tone while rotating around the measuring spot. The research was of theoretical nature and was intended to pave the way for publications to come in the future and avoid overly multidisciplinary papers by separating the physical from the musicological, that we intend on researching more in the future. In summary, at the center of rotation, the velocity vector of the particles of the medium get distorted as the source rotates, resulting in a spectrum split that is equivalent to the angular velocity of rotation. The interesting thing, we find, is, that neither is the source sound is modified, nor are we changing the distance, i.e. the radius of the rotation, meaning that the Doppler effect is also not responsible in any way. Just by rotating are we able to modify what the source emits at the central listening position.
Near the end of the year, we were then finally also able to have our paper accepted with the Journal of the Audio Engineering Society, which elaborates on the above observations. Being a paper that focuses on theoretical work again (although the reviewers requested we include practical examples and implementations), we will show how different rotation behaviors produce spectral splits akin to AM and FM synthesis. Moreover, rotating a source in 3D opens up the possibility to chain perpendicular rotations into complex movements and analyze the resulting spectrum. It is also shown, that this spectrum now differs from what AM and FM synthesis is theoretically able to produce. We can even control the overtones of these spectra by including parametric rotations in the middle, which shift the axis of rotations against each other. When this paper will eventually be published is still open and will probably not happen until 2024 I assume.
A third paper on Panningtable Synthesis (PTS) was presented at the AES convention in New York in the Fall of this year. PTS is an evolution from RPMS, which is originally presented in my Master Thesis over 10 years ago. It is more flexible and efficient than RPMS and is shown to correctly emulate VBAP, meaning it is a valid panning 3D technique in that sense. However, with PTS we can target any sound spectrum resulting from rapid panning motions and the artifacts caused by pair-wise panning (or triplet-wise panning in 3D), just like wavetable synthesis does. Therefore, we can deviate from VBAP and move fluidly anywhere on the parametric space to target either accurate panning coefficients or whichever spectrum we might aim for. It is a powerful tool for 3D sound synthesis and I believe there still more to uncover!
Finally, I am very happy to finally publish research in the field of emotional perception music as a function of its direction of incidence. This means that sound, divided into classes of positive and negative valence, was played from the front, back, left and right to listeners sitting in the center and facing forward. We asked them questions using a self-assessment manikin and also measured their brain activity using a 12 point EEG device. The analysis was done by training an AI on random parts of the acquired EEG data and seeing how reliably it is able to predict the type of music class and direction of incidence. Results showed that the accuracy was well above chance, which is a good sign that it is not entirely pointless to play sounds from different directions. In other words, it matters if a sound comes from the front or the back or the left or right. A lot of research is still necessary to come closer to the question how playing the sound might affect us emotionally. But, for now, we need put our heads back into the labs and continue studying and acquire more data.