PHASE occluder silences direct sound instead of muffling it

Question

Created 3d

Replies 2

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I’m using PHASE for an outdoor soundscape with only .directPathTransmission enabled.

A point source and listener are 2 metres apart. Between them is a PHASEOccluder built from a 2 × 2 × 0.02 metre MDLMesh box, with a .cardboard material assigned to every shape element.

Without the occluder, the sound is loud. With it, the sound is completely inaudible. Switching to .glass and setting the sampler’s cullOption to .doNotCull makes no audible difference. This happens on both iOS Simulator and a physical iPhone.

Adding .lateReverb produces faint audible sound, but room reverb is inappropriate for this outdoor scene and doesn’t establish whether direct transmission works.

Is this expected attenuation, or is additional configuration required to hear muffled sound through an occluder? Is there a working sample demonstrating material-dependent transmission with reverb disabled?

Answer 1

Systems Engineer OP

Apple

15h

Hello! Thanks for reaching out.

Clarifying a couple of things:

The .doNotCull option relates to playback controls on how different nodes in a sound event pause / resume and is not connected to environmental occlusion.
Assuming the thickness between the source and listener in this example is 0.02 meters - are you able to share the position of the source and listener and the occluder transform?
Could you also confirm which iOS version you are running?

We have the following resource available which touches on occluder set up but no specific sample for material-dependent transmission with reverb disabled.

https://developer.apple.com/documentation/phase/playing-sound-from-a-location-in-a-3d-scene

If you have a reproduction you are able to share you can also submit it via Feedback Assistant and we can look into it in more detail:

https://developer.apple.com/feedback-assistant/

Thank you, Pedro

Answer 2

dcutting99 OP

5h

Thanks Pedro. I have created feedback FB24904876 with a sample project.

This is on iOS 27 and macOS 27.

The source is at 0, 0, -1, listener at 0, 0, 1, wall at 0, 0, 0. with extent in the x/y dimensions and 4cm thickness on the z dimension.

I noticed that when the wall is small, a tiny bit of sound is audible, but when the wall is large nothing can be heard, even though the thickness of the wall is the same, and in all cases the source is fully occluded from the listener.

I would expect some sound to be transmitted through the wall no matter the size given the same thickness and positioning.

Maybe I don't understand the PHASE occlusion model. Does PHASE transmit sound through occluders at all? Or does the material choice only affect reflectivity of occluders?