7 ms·

> To overcome this problem, the MIT team rethought the design of a thin-film loudspeaker. Rather than having the entire material vibrate, their design relies on

> To overcome this problem, the MIT team rethought the design of a thin-film loudspeaker. Rather than having the entire material vibrate, their design relies on tiny domes on a thin layer of piezoelectric material which each vibrate individually. These domes, each only a few hair-widths across, are surrounded by spacer layers on the top and bottom of the film that protect them from the mounting surface while still enabling them to vibrate freely. Whoa, does this mean an array of individually addressable micro-speakers becomes feasible? Like pixels in a computer screen, send different signals to each tiny speaker? That would mean craaaazy spatial audio, if I'm not mistaken.

boomlinde 5y ago
It seems like there's no reason for this use case for the speakers to be individually addressable, and that would probably add significant complexity.
- moffkalast 5y ago
  That would be pretty nuts, sending out a digital signal and have a built-in DAC for each emitter. Probably way too much bandwidth for any of the standard busses though.
  - oblio 5y ago
    The thing is, don't we have a ton of higher bandwidth buses already available? I can't imagine the audio interfaces being faster than HDMI 2.0, USB 4/Thunderbolt, DisplayPort 3, etc.
    - moffkalast 5y ago
      I was thinking more in the line of i2c, i2s, spi, uart, since I think all of those that you listed require very extensive circuitry to parse. (At least that's the motherboard makers' excuse to only include like 2 USB 3.0s and 1 USB 3.1 port and like two bazillion 2.0 ports)
  - boomlinde 5y ago
    As an example, a thousand channels of 16-bit samples at 48 kHz adds up to 768 Mbits/s, which is well within USB3 bandwidth many times over. 1000 channels is a rather small array, though. 5000 is still not too much.
    - robbedpeter 5y ago
      A lot of the signal is going to be identical, so a hierarchical distribution with in-place modification based on location would be better than calculating the modification of the sound and sending to thousands of channels.
- voxadam 5y ago
  Maybe you could do something like Holoplot[1] does with their full size beamforming speakers. [1] https://holoplot.com/technology/ https://holoplot.com/technology/
- throw0101a 5y ago
  > speakers to be individually addressable Modern audio codecs/standards (Dolby Atmos, DTS:X) have moved 'beyond' individual speakers, and are now using object-based sound: > Audio becomes an object when it is accompanied by metadata that describes its existence, position and function. An audio object can, therefore, be the sound of a bee flying over your head, the crowd noise, commentary to a sporting event in any language. All this remains fully adjustable on the consumer’s end to their specific listening environment, needs and liking, regardless of the device. * https://www.thebroadcastbridge.com/content/entry/16347/object-based-audio-mixing-a-new-way-to-personalized-listening https://www.thebroadcastbridge.com/content/entry/16347/objec... > Think about this: imagine the sound of a race car speeding around a track. You can see the car approaching in the distance, off on the right side of the screen. As it gets closer, it gets louder and zooms across the screen from right to left, with the resulting Doppler shift of the sound as it goes past you. It screams off the left edge of the screen and continues down the left wall until it disappears into the distance behind you. > A sound designer could, in theory, pan this sound carefully from the Right speaker, through the Center speaker, to the Left speaker, and on down to the Left side surround and the Left rear surround before it faded out entirely. That would be the channel-based way of thinking about the task at hand. > Alternatively, the same designer could associate the sound of that race car with locations (coordinates) that move smoothly across the front of the room and then down the left side of the room. It is the same sound, but now with metadata telling the playback system where it should be from one moment to the next. […] > The second, object-oriented way, is scalable. It doesn’t care how many speakers you have in your room because it is not referencing a specific speaker – just relative locations. Importantly, these locations can include the space above you and around you, enclosing you in a “bubble” of sound. * https://www.trinnov.com/en/blog/posts/what-is-immersive-sound/ https://www.trinnov.com/en/blog/posts/what-is-immersive-soun... * https://en.wikipedia.org/wiki/Dolby_Atmos https://en.wikipedia.org/wiki/Dolby_Atmos * https://en.wikipedia.org/wiki/DTS_(sound_system_company)#DTS:X https://en.wikipedia.org/wiki/DTS_(sound_system_company)#DTS... Given the (x, y, x) co-ordinates of an audio signal/object, the codec algorithm figures out which speaker(s) should get what signal: if the system only has two speakers then you'll generally only have stereo, if you have a 7.1.4 setup (four overhead / in-ceiling speakers) it will probably be more immersive: * https://www.dolby.com/about/support/guide/speaker-setup-guides/7.1.4-overhead-speaker-setup-guide/ https://www.dolby.com/about/support/guide/speaker-setup-guid... * https://www.dolby.com/about/support/guide/speaker-setup-guides/7.1.4-dolby-atmos-enabled-speaker-setup-guide/ https://www.dolby.com/about/support/guide/speaker-setup-guid...
WithinReason 5y ago
Directional audio is produced by sound interacting with your ear, so this would not produce spatial audio (unless you would wrap your head in the thin film speaker). What you want is 1 speaker per ear and a software modelling of the HRTF: https://en.wikipedia.org/wiki/Head-related_transfer_function https://en.wikipedia.org/wiki/Head-related_transfer_function
- unlikelymordant 5y ago
  I think op is talking about beamforming when he talks about directional audio, where a large array of speakers would allow you to e.g. send audio in one direction only. The more speakers, the tighter the control.
  - 0cVlTeIATBs 5y ago
    I think OP means e.g. a video call where each person's voice is played back from where their mouth is displayed on screen.
    - Kaibeezy 5y ago
      I don’t think OP was saying that, but you are. A video layer could be built on the gridlines between the speaker domes. Might need to be quite a large screen for the spacing to work out right. Not for high def video, but good for large displays like talking billboards (ugh, actually).
      - tetris11 5y ago
        urgh actually, indeed
    - dtx1 5y ago
      Or as a Center Speaker in a cinema setup where the voice comes not from "the middle" but out the mouth of an actor
      - 5y ago
extrememacaroni 5y ago
Could one use something like this to make a stealth suit thing that does noise cancellation like headphones do to completely mask the noises of the wearer? That would be cool.
eternauta3k 5y ago
Physics/EE students please correct me, I've mostly forgotten this stuff. Assuming the speaker is many wavelengths away (in the "far field"), the distance between individual speakers needs to be larger (comparable with the wavelength) to make a difference in the radiation pattern in the far field. Speakers which are closer together only make a difference in the near field (meaning the listener is within a few wavelengths of the array). If you want to understand this, look into https://en.wikipedia.org/wiki/Phased_array https://en.wikipedia.org/wiki/Phased_array
- sandpaper26 5y ago
  While there is certainly a difference between near- and far-field approximations, the short answer is that no, the speakers can be closer than one wavelength together in order to have a steerable far field. In fact, the link you provided has a 1/4 wavelength spaced array as one of its first examples. You may be confused here because typically it is harder to make lower frequency waves from a single emitter more directional -- but that has more to do with waveguide and aperture geometry.
  - eternauta3k 5y ago
    Looking at the equation for the radiation pattern of the phased array, the angle dependence goes like sin(pi * (N * d/lambda) * sin theta). If N * d (i.e. the size of the array) is much smaller than lambda, there's no interference pattern. To be more precise, for the radiation pattern to have a null, N * d must be larger than the wavelength.
    - sandpaper26 5y ago
      Yes, but I think that's why you're confused. The distance between the individual speakers would be d, not N*d. Because your original comment was about this spacing, that's what I addressed in my answer. Obviously a larger effective aperture (either physical or synthetic) would be more effective at beam steering.
traceroute66 5y ago
> To overcome this problem, the MIT team rethought the design of a thin-film loudspeaker. I wonder if the team has seen Sony's OLED TV's with Acoustic Surface ? The screen itself is used as a large speaker, and its surprisingly good.
- deleted 5y ago
  [deleted]
- tigershark 5y ago
  The Sony solution actually has subwoofers hidden inside for the bass. I’m still missing how this paper-thin solution could possibly produce any decent bass.
  - Applejinx 5y ago
    It absolutely can't. This is a tweeter design. Might be good as that. It's not going to have even enough excursion to do midbass or lower midrange. Mind you if the description is correct, to hear it properly they need to adhere it to a physical object. Having it dangling in free air like that means it's a lobed omnidirectional radiator: opposite of a dipole, it's putting out the same signal to either side across the whole plane, and the edges aren't putting out anything, and the range isn't low enough to hear it side-on very well: highs are directional. This is why when he curves it you hear treble louder: it's making a little dish aimed at the mic (roughly). You could easily make a tweeter for 'head in a vice imaging' where the curvature is such that it's aimed only at the ear position, for less near reflections off walls. As described, you'd always want to back it with a physical object. In a large enough area it's a midrange driver with very high peak output in the highs. You could curve it the opposite direction to make the mids slightly dominate over the highs: slight off-axis will attenuate highs a little more than mids, and the differences in hearing position across the curved surface (it's a smooth radiator without any specific driving points) will cause higher frequencies to cancel, again reinforcing lower frequency stuff.

boomlinde 5y ago

It seems like there's no reason for this use case for the speakers to be individually addressable, and that would probably add significant complexity.

moffkalast 5y ago
That would be pretty nuts, sending out a digital signal and have a built-in DAC for each emitter. Probably way too much bandwidth for any of the standard busses though.
- oblio 5y ago
  The thing is, don't we have a ton of higher bandwidth buses already available? I can't imagine the audio interfaces being faster than HDMI 2.0, USB 4/Thunderbolt, DisplayPort 3, etc.
  - moffkalast 5y ago
    I was thinking more in the line of i2c, i2s, spi, uart, since I think all of those that you listed require very extensive circuitry to parse. (At least that's the motherboard makers' excuse to only include like 2 USB 3.0s and 1 USB 3.1 port and like two bazillion 2.0 ports)
- boomlinde 5y ago
  As an example, a thousand channels of 16-bit samples at 48 kHz adds up to 768 Mbits/s, which is well within USB3 bandwidth many times over. 1000 channels is a rather small array, though. 5000 is still not too much.
  - robbedpeter 5y ago
    A lot of the signal is going to be identical, so a hierarchical distribution with in-place modification based on location would be better than calculating the modification of the sound and sending to thousands of channels.
voxadam 5y ago
Maybe you could do something like Holoplot[1] does with their full size beamforming speakers. [1] https://holoplot.com/technology/ https://holoplot.com/technology/
throw0101a 5y ago
> speakers to be individually addressable Modern audio codecs/standards (Dolby Atmos, DTS:X) have moved 'beyond' individual speakers, and are now using object-based sound: > Audio becomes an object when it is accompanied by metadata that describes its existence, position and function. An audio object can, therefore, be the sound of a bee flying over your head, the crowd noise, commentary to a sporting event in any language. All this remains fully adjustable on the consumer’s end to their specific listening environment, needs and liking, regardless of the device. * https://www.thebroadcastbridge.com/content/entry/16347/object-based-audio-mixing-a-new-way-to-personalized-listening https://www.thebroadcastbridge.com/content/entry/16347/objec... > Think about this: imagine the sound of a race car speeding around a track. You can see the car approaching in the distance, off on the right side of the screen. As it gets closer, it gets louder and zooms across the screen from right to left, with the resulting Doppler shift of the sound as it goes past you. It screams off the left edge of the screen and continues down the left wall until it disappears into the distance behind you. > A sound designer could, in theory, pan this sound carefully from the Right speaker, through the Center speaker, to the Left speaker, and on down to the Left side surround and the Left rear surround before it faded out entirely. That would be the channel-based way of thinking about the task at hand. > Alternatively, the same designer could associate the sound of that race car with locations (coordinates) that move smoothly across the front of the room and then down the left side of the room. It is the same sound, but now with metadata telling the playback system where it should be from one moment to the next. […] > The second, object-oriented way, is scalable. It doesn’t care how many speakers you have in your room because it is not referencing a specific speaker – just relative locations. Importantly, these locations can include the space above you and around you, enclosing you in a “bubble” of sound. * https://www.trinnov.com/en/blog/posts/what-is-immersive-sound/ https://www.trinnov.com/en/blog/posts/what-is-immersive-soun... * https://en.wikipedia.org/wiki/Dolby_Atmos https://en.wikipedia.org/wiki/Dolby_Atmos * https://en.wikipedia.org/wiki/DTS_(sound_system_company)#DTS:X https://en.wikipedia.org/wiki/DTS_(sound_system_company)#DTS... Given the (x, y, x) co-ordinates of an audio signal/object, the codec algorithm figures out which speaker(s) should get what signal: if the system only has two speakers then you'll generally only have stereo, if you have a 7.1.4 setup (four overhead / in-ceiling speakers) it will probably be more immersive: * https://www.dolby.com/about/support/guide/speaker-setup-guides/7.1.4-overhead-speaker-setup-guide/ https://www.dolby.com/about/support/guide/speaker-setup-guid... * https://www.dolby.com/about/support/guide/speaker-setup-guides/7.1.4-dolby-atmos-enabled-speaker-setup-guide/ https://www.dolby.com/about/support/guide/speaker-setup-guid...

WithinReason 5y ago

Directional audio is produced by sound interacting with your ear, so this would not produce spatial audio (unless you would wrap your head in the thin film speaker). What you want is 1 speaker per ear and a software modelling of the HRTF: https://en.wikipedia.org/wiki/Head-related_transfer_function https://en.wikipedia.org/wiki/Head-related_transfer_function

unlikelymordant 5y ago
I think op is talking about beamforming when he talks about directional audio, where a large array of speakers would allow you to e.g. send audio in one direction only. The more speakers, the tighter the control.
- 0cVlTeIATBs 5y ago
  I think OP means e.g. a video call where each person's voice is played back from where their mouth is displayed on screen.
  - Kaibeezy 5y ago
    I don’t think OP was saying that, but you are. A video layer could be built on the gridlines between the speaker domes. Might need to be quite a large screen for the spacing to work out right. Not for high def video, but good for large displays like talking billboards (ugh, actually).
    - tetris11 5y ago
      urgh actually, indeed
  - dtx1 5y ago
    Or as a Center Speaker in a cinema setup where the voice comes not from "the middle" but out the mouth of an actor
    - 5y ago

extrememacaroni 5y ago

Could one use something like this to make a stealth suit thing that does noise cancellation like headphones do to completely mask the noises of the wearer? That would be cool.

eternauta3k 5y ago

Physics/EE students please correct me, I've mostly forgotten this stuff. Assuming the speaker is many wavelengths away (in the "far field"), the distance between individual speakers needs to be larger (comparable with the wavelength) to make a difference in the radiation pattern in the far field. Speakers which are closer together only make a difference in the near field (meaning the listener is within a few wavelengths of the array). If you want to understand this, look into https://en.wikipedia.org/wiki/Phased_array https://en.wikipedia.org/wiki/Phased_array

sandpaper26 5y ago
While there is certainly a difference between near- and far-field approximations, the short answer is that no, the speakers can be closer than one wavelength together in order to have a steerable far field. In fact, the link you provided has a 1/4 wavelength spaced array as one of its first examples. You may be confused here because typically it is harder to make lower frequency waves from a single emitter more directional -- but that has more to do with waveguide and aperture geometry.
- eternauta3k 5y ago
  Looking at the equation for the radiation pattern of the phased array, the angle dependence goes like sin(pi * (N * d/lambda) * sin theta). If N * d (i.e. the size of the array) is much smaller than lambda, there's no interference pattern. To be more precise, for the radiation pattern to have a null, N * d must be larger than the wavelength.
  - sandpaper26 5y ago
    Yes, but I think that's why you're confused. The distance between the individual speakers would be d, not N*d. Because your original comment was about this spacing, that's what I addressed in my answer. Obviously a larger effective aperture (either physical or synthetic) would be more effective at beam steering.

traceroute66 5y ago

> To overcome this problem, the MIT team rethought the design of a thin-film loudspeaker. I wonder if the team has seen Sony's OLED TV's with Acoustic Surface ? The screen itself is used as a large speaker, and its surprisingly good.

deleted 5y ago
[deleted]
tigershark 5y ago
The Sony solution actually has subwoofers hidden inside for the bass. I’m still missing how this paper-thin solution could possibly produce any decent bass.
- Applejinx 5y ago
  It absolutely can't. This is a tweeter design. Might be good as that. It's not going to have even enough excursion to do midbass or lower midrange. Mind you if the description is correct, to hear it properly they need to adhere it to a physical object. Having it dangling in free air like that means it's a lobed omnidirectional radiator: opposite of a dipole, it's putting out the same signal to either side across the whole plane, and the edges aren't putting out anything, and the range isn't low enough to hear it side-on very well: highs are directional. This is why when he curves it you hear treble louder: it's making a little dish aimed at the mic (roughly). You could easily make a tweeter for 'head in a vice imaging' where the curvature is such that it's aimed only at the ear position, for less near reflections off walls. As described, you'd always want to back it with a physical object. In a large enough area it's a midrange driver with very high peak output in the highs. You could curve it the opposite direction to make the mids slightly dominate over the highs: slight off-axis will attenuate highs a little more than mids, and the differences in hearing position across the curved surface (it's a smooth radiator without any specific driving points) will cause higher frequencies to cancel, again reinforcing lower frequency stuff.