[LAU] How I built my own IR reverb in ambisonics

Fons Adriaensen fons at linuxaudio.org
Wed Sep 21 15:35:22 CEST 2022

On Wed, Sep 21, 2022 at 02:02:58AM +0200, Michael Jarosch wrote:

> After that I took a
> paper bag to create an impulse, about 50cm away from the NT-SF1.

If the room is big enough, you could use a larger distance.
This will reduce the amplitude of the the impulse but not
the room response, so you could have a better S/N ratio.

A paper bag (or balloon) is not ideal, there are alternatives,
see below.

> The only tool in my procedure that wasn't free and open was Rødes Soundfield
> PlugIn, so I had to use some tricks to get manufacturer proven A-to-B
> conversion of my recordings.

There is NT1 preset available for tetraproc (real-time A/B processor, Jack)
and tetrafile (file processor doing the same). I can send it if you want.

The method of choice today is not to use balloons or pistols, but
a logarithmic sweep signal and deconvolution with the inverse sweep.
This will give you

1. A more correct result, since the spectrum of the test signal is
exactly known (apart from the speaker used to play it),

2. A much better S/N ratio since the test signal can be several
seconds long so it has much more energy at the same amplitude as a
popping balloon.



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