11 ms·

This is great, I'm watching the video on YouTube now... Are exhausts/mufflers modelled? For ages I've wanted to simulate different designs for exhaust headers

by jb_s 4y ago

This is great, I'm watching the video on YouTube now... Are exhausts/mufflers modelled? For ages I've wanted to simulate different designs for exhaust headers and systems, to be able to possibly create different/interesting sounds from certain engines - i.e. can you add some additional headers with a different length and make an I4 sound like an I6?

tonmoy 4y ago
If I recall correctly he modeled the acoustics of the exhaust using equalizers and filters, so not really simulated
- Cloudef 4y ago
  Could use convolution with recorded impulse response (IR) files to achieve realistic results for different exhausts.
  - tonmoy 4y ago
    Not sure how one would be able to obtain impulse response of the exhaust system
    - deleted 4y ago
      [deleted]
    - userbinator 4y ago
      You can model it as a series of tubes of different diameters. Look up "digital waveguide" for some more details. This technique is mostly used in speech synthesis, where it can make pretty realistic human-speech-like sounds by modelling the vocal tract, but there's no reason it can't be applied to a car exhaust system.
      - ynniv 4y ago
        The better car simulators already do this: “Physically informed car engine sound synthesis for virtual and augmented environments” https://air.iuav.it/bitstream/11578/264484/1/SIVE15_submission_4.pdf https://air.iuav.it/bitstream/11578/264484/1/SIVE15_submissi...
    - Cloudef 4y ago
      Guitarists (or mixers) record IRs by playing a sine wave through their cab and recording that. The difference from the dry vs recorded sample is then your IR. While exhaust systems have no digital input, if you have good enough audio gear that can output the signal dry as possible through the exhaust setup, it should achieve the same result I guess. Not that trivial for everyone to do, but if you do this enough times for different kind of exhausts, you'll also have great dataset to start researching and developing a software that can model exhausts accurately.
- chillel 4y ago
  I think you mean acoustics, not autistics =)
  - Inviz 4y ago
    Funnily enough on YouTube in certain areas "acoustic" became a synonym for "autistic"
- xbar 4y ago
  A second simulator for exhaust systems would be appealing. Perhaps he will figure it out himself, or re-open source the existing simulation once he figures out how to get the credit/compensation he deserves.
  - mhh__ 4y ago
    I think the issue would be that whereas this I think can get away with just a really fast rigid body simulation, the exhausts and so on would need to simulate acoustics where you have feature sizes in the same ballpark as the wavelength of the sound i.e. your ear will almost definitely be a harsh critic.
    - atoav 4y ago
      I mean there are models in acoustic physical modelling for e.g. throat simulation that break the throat up into a series of cylinders and frustrums that work quite ok. Not sure about real time performance tho.
      - userbinator 4y ago
        Works well enough for decent speech synthesis, in realtime.

by jb_s 4y ago

tonmoy 4y ago

If I recall correctly he modeled the acoustics of the exhaust using equalizers and filters, so not really simulated

Cloudef 4y ago
Could use convolution with recorded impulse response (IR) files to achieve realistic results for different exhausts.
- tonmoy 4y ago
  Not sure how one would be able to obtain impulse response of the exhaust system
  - deleted 4y ago
    [deleted]
  - userbinator 4y ago
    You can model it as a series of tubes of different diameters. Look up "digital waveguide" for some more details. This technique is mostly used in speech synthesis, where it can make pretty realistic human-speech-like sounds by modelling the vocal tract, but there's no reason it can't be applied to a car exhaust system.
    - ynniv 4y ago
      The better car simulators already do this: “Physically informed car engine sound synthesis for virtual and augmented environments” https://air.iuav.it/bitstream/11578/264484/1/SIVE15_submission_4.pdf https://air.iuav.it/bitstream/11578/264484/1/SIVE15_submissi...
  - Cloudef 4y ago
    Guitarists (or mixers) record IRs by playing a sine wave through their cab and recording that. The difference from the dry vs recorded sample is then your IR. While exhaust systems have no digital input, if you have good enough audio gear that can output the signal dry as possible through the exhaust setup, it should achieve the same result I guess. Not that trivial for everyone to do, but if you do this enough times for different kind of exhausts, you'll also have great dataset to start researching and developing a software that can model exhausts accurately.
chillel 4y ago
I think you mean acoustics, not autistics =)
- Inviz 4y ago
  Funnily enough on YouTube in certain areas "acoustic" became a synonym for "autistic"
xbar 4y ago
A second simulator for exhaust systems would be appealing. Perhaps he will figure it out himself, or re-open source the existing simulation once he figures out how to get the credit/compensation he deserves.
- mhh__ 4y ago
  I think the issue would be that whereas this I think can get away with just a really fast rigid body simulation, the exhausts and so on would need to simulate acoustics where you have feature sizes in the same ballpark as the wavelength of the sound i.e. your ear will almost definitely be a harsh critic.
  - atoav 4y ago
    I mean there are models in acoustic physical modelling for e.g. throat simulation that break the throat up into a series of cylinders and frustrums that work quite ok. Not sure about real time performance tho.
    - userbinator 4y ago
      Works well enough for decent speech synthesis, in realtime.