Did We Miss Something?
At a recent show a team from Postech (Pohang University of Science & Technology) in Korea demonstrated a system that produced sound as part of a 13” OLED display. The team was very specific as to what this proof of concept system was and how it worked but for some reason a number of tech rags picked up the story and transformed it into one where the implication was that the OLED pixels were generating sound. As far as we could see, this was not the case and the implication that ‘eventually every pixel in the display could act as a speaker’ was a figment of someone’s imagination and had no bearing on the concept shown.
The idea of embedding sound generation directly into a display has been around for years. LG Display (LPL) has been demonstrating its “Crystal Sound” system at shows for years, and Sony (SNE) has their ‘Acoustic Surface Audio’ system, both of which use electro-magnetic speakers attached to a frame that surrounds the OLED display. These transducers (speaker) work, just the way your stereo speakers or even the speakers in your smartphone work, by sending an audio signal to a voice coil (an electromagnet), which interrupts a permanent magnetic field and moves a diaphragm. That diaphragm creates sound waves, and you hear music or speech. Unfortunately these ‘exciters’ are thick and not conducive to the ultra-thin displays in current use, but they also have another problem.
External speakers, such as a soundbar or individual speakers placed in a room are isolated from each other, while the speakers in the systems mentioned above are attached to the same frame. This causes them to interact with each other which creates peaks and valleys in the sound that are not part of the content or music. As the human ear is very sensitive to loudness levels, this can make the sound less than perfect. Some have tried using piezoelectric speakers, which convert an audio signal directly into diaphragm movement (no voice coil), which are thinner and less expensive, but they still interact with each other if mounted on the same display frame.
What the team from Postech did was to embellish the display frame by creating nine isolated sections in the frame with an exciter in each. This reduced the interaction between each exciter and allowed each exciter location to operate independently of the other, creating a localized sound from each of the nine locations on the display. This was certainly an accomplishment and indicated that it was possible to create a display that was able to localize sound across the display, without the distortion typically generated by a single frame. Whether this is a everyday solution for display sound remains to be seen both from a practical and a cost standpoint, but it had little to do with the OLED pixels. In fact the only reason an OLED display was being used as a test bed was because LCD and Mini-LED displays have too many layers that dampen the vibration of the frame.
So, taking the idea to its ultimate goal, attaching millions of piezoic speakers to a system that would ‘vibrate every pixel and turn each into a sound source’ was not really part of the demo, nor does it seem even remotely practical. In order to create sound, the ‘millions of piezoic exciters’ would have to be attached to a frame, so we are talking about a frame that must be at least somewhat rigid yet able to adhere to millions of very tiny speakers and each of the millions of exciters would have to be isolated from each other, an almost impossible task. Perhaps that can be accomplished someday using a lithographic process at a cost that is reasonable, but there is another problem.
In order for this system to originate localized sound at every pixel, the ultimate objective, the sound would have to be separated into a grid with a million localized horizontal and vertical points and each point in such a matrix would have to have a connection to one of the million exciters. This is similar to how each pixel receives video information from a display system’s video processor, a complex task at best. Doing this for audio would add considerably to the cost and complexity of any such system. Again almost anything can be done with silicon, but at what cost and for what gain?
The idea of localizing sound across a display is conceptually sound (sorry!) but not nearly as necessary or as practical as it might seem, although object-oriented sound recording would work in favor of such a system. If one were to use 1” square exciters for a 65” TV, it would require ~1,800 exciters, a frame that could isolate them all, the power necessary to drive 1,800 speakers, and a system to assign the audio matrix to each speaker. That seems to be a bit of overkill. More practical both from a structural and a practical one might be eighteen 10” exciters, each covering a 10” square section of the screen. Do we really need to be that precise as to the location of a spoon falling to the floor?
The idea of embedding sound generation directly into a display has been around for years. LG Display (LPL) has been demonstrating its “Crystal Sound” system at shows for years, and Sony (SNE) has their ‘Acoustic Surface Audio’ system, both of which use electro-magnetic speakers attached to a frame that surrounds the OLED display. These transducers (speaker) work, just the way your stereo speakers or even the speakers in your smartphone work, by sending an audio signal to a voice coil (an electromagnet), which interrupts a permanent magnetic field and moves a diaphragm. That diaphragm creates sound waves, and you hear music or speech. Unfortunately these ‘exciters’ are thick and not conducive to the ultra-thin displays in current use, but they also have another problem.
External speakers, such as a soundbar or individual speakers placed in a room are isolated from each other, while the speakers in the systems mentioned above are attached to the same frame. This causes them to interact with each other which creates peaks and valleys in the sound that are not part of the content or music. As the human ear is very sensitive to loudness levels, this can make the sound less than perfect. Some have tried using piezoelectric speakers, which convert an audio signal directly into diaphragm movement (no voice coil), which are thinner and less expensive, but they still interact with each other if mounted on the same display frame.
What the team from Postech did was to embellish the display frame by creating nine isolated sections in the frame with an exciter in each. This reduced the interaction between each exciter and allowed each exciter location to operate independently of the other, creating a localized sound from each of the nine locations on the display. This was certainly an accomplishment and indicated that it was possible to create a display that was able to localize sound across the display, without the distortion typically generated by a single frame. Whether this is a everyday solution for display sound remains to be seen both from a practical and a cost standpoint, but it had little to do with the OLED pixels. In fact the only reason an OLED display was being used as a test bed was because LCD and Mini-LED displays have too many layers that dampen the vibration of the frame.
So, taking the idea to its ultimate goal, attaching millions of piezoic speakers to a system that would ‘vibrate every pixel and turn each into a sound source’ was not really part of the demo, nor does it seem even remotely practical. In order to create sound, the ‘millions of piezoic exciters’ would have to be attached to a frame, so we are talking about a frame that must be at least somewhat rigid yet able to adhere to millions of very tiny speakers and each of the millions of exciters would have to be isolated from each other, an almost impossible task. Perhaps that can be accomplished someday using a lithographic process at a cost that is reasonable, but there is another problem.
In order for this system to originate localized sound at every pixel, the ultimate objective, the sound would have to be separated into a grid with a million localized horizontal and vertical points and each point in such a matrix would have to have a connection to one of the million exciters. This is similar to how each pixel receives video information from a display system’s video processor, a complex task at best. Doing this for audio would add considerably to the cost and complexity of any such system. Again almost anything can be done with silicon, but at what cost and for what gain?
The idea of localizing sound across a display is conceptually sound (sorry!) but not nearly as necessary or as practical as it might seem, although object-oriented sound recording would work in favor of such a system. If one were to use 1” square exciters for a 65” TV, it would require ~1,800 exciters, a frame that could isolate them all, the power necessary to drive 1,800 speakers, and a system to assign the audio matrix to each speaker. That seems to be a bit of overkill. More practical both from a structural and a practical one might be eighteen 10” exciters, each covering a 10” square section of the screen. Do we really need to be that precise as to the location of a spoon falling to the floor?
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