Would that sample sweep be what I would play through my recorder in order to
make a reverb of a space?
-----Original Message-----
From: audacity4blind-bounce@xxxxxxxxxxxxx
[mailto:audacity4blind-bounce@xxxxxxxxxxxxx] On Behalf Of Robert Hänggi
Sent: Thursday, August 22, 2019 10:12 AM
To: audacity4blind@xxxxxxxxxxxxx
Subject: [audacity4blind] Re: Recording Impulse Responses
Hi Annabelle.
Have you tried Voxengo deconvolver?
It processes audio recordings that you've made and creates the impulse
responses from it.
A test tone generator (sweep sounds) is included.
I attach a sample sweep.
The demo version should be fully functional, I think. However, it is a bit
tricky to find it as the application is no longer maintained, if I recall
correctly.
The subject is certainly interesting. But remember that the impulse you get is
not necessarily the right one.
Here are some random thoughts of mine, without having gone deep into the
matter:
1. The exciting sounds should cover the whole spectrum 2. they should be
reproducible, i.e. identical each time 3. analogue sounds (claps, pistol shots
etc.) are fulfilling point 1 as they are not subject to a limited frequency
range and being coloured by a player/speaker module.
4. playing sweeps satisfies point 2 but have to be processed afterwards.
5. short impulses have to be very loud. Imagine having one sine tone at -20
dB. You combine it with another one which gives you -14 dB etc.
6. For the analysis you need hundreds of frequencies covered which gives you
naturally less amplitude for a given bin 7. sweeps drag the volume over time
and you can thus go with less.
8. player and microphone have to be neutralized in order to get the pure room.
I find it curious that procedures for recording IRs rely on a single volume
setup.
I would therefore create test tones at different levels (compare clapping with
different strength, what reflections do you get at low
volume?)
The idea is that you will at first record only the direct source and the
colouring through playback and recording device. The subsequent sweeps do
excite the room more and more.
This allows us to get a trend and extrapolate a response for a exciting tone
at an otherwise not achievable level, especially for the environment you want
to aim for.
If I had to design a test tone, it would:
- consist of sine tones at FFT bins (e.g. 44100 Hz divided by 1024 or
2048 etc) and at 3 different levels. Naturally, this would be a very long
tone, however, some tones that are not correlated can be stacked.
Of course, this needs a custom processing module but Nyquist should be able to
do that.
Sorry for the lengthy email.
Robert
The audacity4blind web site is at
//www.freelists.org/webpage/audacity4blind
Subscribe and unsubscribe information, message archives,
Audacity keyboard commands, and more...
To unsubscribe from audacity4blind, send an email to
audacity4blind-request@xxxxxxxxxxxxx
with subject line
unsubscribe
