Open madskjeldgaard opened 1 year ago
The abstract from the Jérôme Daniel paper might be helpful in clearing this up:
Higher Order Ambisonics have been increasingly investigated in the past years, and found promising as a rational, scalable and flexible way to encode, transmit and render 3D sound fields. Nevertheless, studies concerning virtual source imaging or natural 3D sound encoding mainly focussed on the directional encoding of plane waves, and neglected the near field effect of finite distance sources though it's present in any ordinary sound field. This paper highlights that with near field, the infinite bass-boost affecting ambisonic components makes the currently accepted format unviable. By introducing from the encoding stage a near field compensation of reproduction loudspeakers, a viable, modified ambisonic format is defined, distance-coding filters are designed, and higher order ambisonic recording and synthesis become practicable.
Hello @madskjeldgaard,
Yep, the problem is, if we directly use infinity referenced proximity, we get super high gains when sources are in the near-field. Daniel's NFE solution is to pre-filter to a radius in the mid-field. We can still blow things up with near-field sources, but we have a lot more room (radius, actually!) to work with.
Good idea to include some more info regarding Daniel's comments.
Hey everyone!
Thanks again for the amazing work here. I've been reading the HOA-NFE file today, and I've come to a realization as to why I am having a bit of trouble understanding this document.
It seems to me that in the explanation of the virtues of the HOA-NFE variant, there is something missing that might make it easier to understand, specifically in this part:
What seems to be missing for me in this explanation is the prerequisite of knowing what the problem actually is that HOA-NFE solves here. Why is it nice that Daniel translated the basic wave to a radius other than inf? In other words, what's the selling point for NFE in (something slightly closer to) layman's terms? I think this might clear up the explanation, at least for me.
Thanks again!
best