The Science Behind the Yuni
The Yuni produces single-sided stereo sound by taking advantage of a special feature of the human auditory system. The way we know where sounds are coming from is from a process called "localization," and we have a few different ways of localizing the position and distance of sound sources.
While standard stereo headphones make use of our horizontal localization capabilities, specifically binaural (i.e., "two-eared") horizontal localization, the Yuni uses our vertical localization abilities to achieve single-sided stereo.
Here's how it works: the shape of our outer ear changes the perceived frequency of sounds slightly depending on what angle the sound waves approach the ear from. Our brains know how to decode this shift in frequency to determine roughly where a sound is relative to our ear, which is how we know whether a sound is coming from above or below or ear.
Test it out: if you make a sound with your fingers, then move it up and down past your ear, you should be able to tell whether the sound is coming from above or below your ear. The Yuni just uses an "up" and "down" channel, instead of "left" and "right" channels as a normal headphone would--one speaker above the ear opening and one below the ear opening, so that the ear perceives two different sound sources coming from two different directions. Just like stereo, but with a single ear!
Please refer to Risoud et al. (2018), specifically Section 2.2: Vertical Localization, for a literature review of how the outer ear (i.e., the pinna) localizes the elevation of sound.
While standard stereo headphones make use of our horizontal localization capabilities, specifically binaural (i.e., "two-eared") horizontal localization, the Yuni uses our vertical localization abilities to achieve single-sided stereo.
Here's how it works: the shape of our outer ear changes the perceived frequency of sounds slightly depending on what angle the sound waves approach the ear from. Our brains know how to decode this shift in frequency to determine roughly where a sound is relative to our ear, which is how we know whether a sound is coming from above or below or ear.
Test it out: if you make a sound with your fingers, then move it up and down past your ear, you should be able to tell whether the sound is coming from above or below your ear. The Yuni just uses an "up" and "down" channel, instead of "left" and "right" channels as a normal headphone would--one speaker above the ear opening and one below the ear opening, so that the ear perceives two different sound sources coming from two different directions. Just like stereo, but with a single ear!
Please refer to Risoud et al. (2018), specifically Section 2.2: Vertical Localization, for a literature review of how the outer ear (i.e., the pinna) localizes the elevation of sound.