How about a percussion instrument such as a sand block, if that is the correct
term? Whatever the correct name is, either that or something else I don't know
about that is a percussion instrument should serve.
Gene
----- Original Message -----
I'm curious what the purpose is. Evidently, from the very little bit I've
read, you want an impression of the area acoustically, such as if ther4e is an
anechoid qquality or if it sounds as though space is cramped or something of
the sort. But what would such an impression be used for?
Gene
----- Original Message -----
From: Annabelle Susan Morison
Sent: Wednesday, August 28, 2019 11:02 PM
To: audacity4blind@xxxxxxxxxxxxx
Subject: [audacity4blind] Re: Recording Impulse Responses
Hey Robert,
I talked with my friend Markus Johnson (Yes, that's "Markus" with a "K", not a
"C"), and he says that snapping a mouse trap would be dangerous for me. So I'm
not sure where to turn, especially when it comes to sound sources for an
impulse response. I tried a handclap, but unfortunately it makes my hands
sting. Maybe I'm doing something wrong. Markus suggested a gunshot, but
something like that, even if it's a starter pistol, wouldn't be allowed in a
place like an airport. What do I do next?
-----Original Message-----
From: audacity4blind-bounce@xxxxxxxxxxxxx
[mailto:audacity4blind-bounce@xxxxxxxxxxxxx] On Behalf Of Robert Hänggi
Sent: Saturday, August 24, 2019 9:06 PM
To: audacity4blind@xxxxxxxxxxxxx
Subject: [audacity4blind] Re: Recording Impulse Responses
Any short burst of sound will scare someone.
You can give the handclap a try for a beginning.
In order to make it somewhat predictable, use always the same technique. The
Spanish have a name for it but I can't remember right now.
Struck the inside/palm of your hand with three fingers such that the tips just
align with the life line, i.e the second hand is shifted below the wrist of
the other one. That gives a tighter sound and is not so hollow.
Robert
On 24/08/2019, Annabelle Susan Morison <foristnights@xxxxxxxxxxx> wrote:
Hopefully a mouse trap won't scare anyone in an airport terminal!
Someone might mistake it for a gun. And, hopefully I can spring it in
such a way that it won't smash my fingers. The player? I'm confused!
-----Original Message-----
From: audacity4blind-bounce@xxxxxxxxxxxxx
[mailto:audacity4blind-bounce@xxxxxxxxxxxxx] On Behalf Of Robert
Hänggi
Sent: Saturday, August 24, 2019 2:04 PM
To: audacity4blind@xxxxxxxxxxxxx
Subject: [audacity4blind] Re: Recording Impulse Responses
On 24/08/2019, Annabelle Susan Morison <foristnights@xxxxxxxxxxx> wrote:
I've contacted Olympus America, and it turns out that you can'tHm, I think the player wouldn't have the fidelity anyway, no real bass
actually record while playing back a file on the LS100. So I'm
wondering if I may have to go back to the idea of bubble wrap, a
balloon pop, a handclap, a fingersnap, or a foot stomp for an impulse
response signal.
for instance and there also might be some bleeding, if only due to the
vibration
during playback.
It had to be a ghetto blaster or something like that.
As I said, you want to have a sound that is repeatable. This rules all
the things you've listed actually out.
A clapper would be good but you're not executing the same pressure
each time.
The only mechanical device that is cheap and has that repeatable
property is
-
don't laugh - a mouse trap.
The tension of the spring is always the same.
I would however use a different material since the wood is too soft.
I have for instance a clapper made of two stone bars. They are
perfectly smooth and polished - some rest posts of kitchen coverings.
To my ears, they have the most neutral sound.
Robert
-----Original Message-----
From: audacity4blind-bounce@xxxxxxxxxxxxx
[mailto:audacity4blind-bounce@xxxxxxxxxxxxx] On Behalf Of Robert
Hänggi
Sent: Thursday, August 22, 2019 3:02 PM
To: audacity4blind@xxxxxxxxxxxxx
Subject: [audacity4blind] Re: Recording Impulse Responses
Yes, in general, the room has to be quiet.
Mind, not empty.
That's where the fault lies in almost all impulse responses you can get.
What is it worth to have the characteristics of the Boston
Philharmonic hall
in order to mock up your orchestral sounds?
It won't be real because you've neglected the presence of the artists
and their instruments, not to mention the audience.
Again, if it is crowded, you have to record multiple versions in
succession.
You can either average all the recordings or use vocal reduction and
isolation to isolate what's common to two versions combined in a
stereo track (I would
write a macro for this, if I were you).
First, compose the test track, initial silence, then sweep followed
by min.
3
seconds silence. Use repeat to make the two latter ones last 30
seconds or so.
Append a click at the end (makes aligning easier).
Start small and record the impulse response of your bath room.
Recording A, without background noise; this allows you to judge the
overall
deviation.
Recording B with a bit of noise, e.g. quiet talk.
Goal is here to find a method that filters out the unwanted sounds
and achieves a comparable result to version A.
It also would be good to have a recording from within a sound-dead
location
(on a salt lake on a windless day or a fully stuffed closet).
Robert
On 22/08/2019, Annabelle Susan Morison <foristnights@xxxxxxxxxxx> wrote:
So I could play back your sweep tone and record the space of an airport?
Would
it have to be in an empty terminal? I ask this because if I was to
go to the
Eugene Airport between 2:00 and 5:00 on a Wednesday afternoon, there
would probably be a big crowd there waiting for their planes.
-----Original Message-----
From: audacity4blind-bounce@xxxxxxxxxxxxx
[mailto:audacity4blind-bounce@xxxxxxxxxxxxx] On Behalf Of Robert
Hänggi
Sent: Thursday, August 22, 2019 12:56 PM
To: audacity4blind@xxxxxxxxxxxxx
Subject: [audacity4blind] Re: Recording Impulse Responses
That would be great.
Try it out then.
On 22/08/2019, Annabelle Susan Morison <foristnights@xxxxxxxxxxx> wrote:
My recorder has a "Play Sync" mode, which I believe is when you can
play back a recorded file and record at the same time.
-----Original Message-----
From: audacity4blind-bounce@xxxxxxxxxxxxx
[mailto:audacity4blind-bounce@xxxxxxxxxxxxx] On Behalf Of Robert
Hänggi
Sent: Thursday, August 22, 2019 10:42 AM
To: audacity4blind@xxxxxxxxxxxxx
Subject: [audacity4blind] Re: Recording Impulse Responses
It depends. Can you play and record at the same time?
On 22/08/2019, Annabelle Susan Morison <foristnights@xxxxxxxxxxx>
wrote:
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
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