28 Jan
2011
28 Jan
'11
7:40 a.m.
Hi all,
I know that there are some knowledgable people on this list, hence this OT
diversion.
A friend of mine would like to record some impulse response of various
spaces. I don't know the details nor the ultimate goal of this undertaking
but the problem was about the bst equipment for such recordings. I know a
loud signal is needed (she has a starter gun for that purpose) but unclear
about what kind of microphones should be used. Any tips? Ideas?
experiences?
Thanks a ton in advance.
./MiS
28 Jan
28 Jan
11 a.m.
Hello Michal!
A starter gun is/was used often, but isn't the best of ideas, if you can
help it. The energie in all the different frequency bands of the reverb is too
low. If your friend is willing to use Aliki, then she'll have a frequency
sweep done with a sine wave. Of course for that, she'd also need a speaker or
two to let that blare through the space. Nice thing about it: The speaker
doesn't have to be top quality, it can distort a little without damaging the
resulting IR.
As to microphones: Not aexactly sure, but there are mics preferred for
ambient recordings. Otherwise I'd say every mic, that can pick a good deal of
frequencies with a relatively flat response. Not sure about the
characteristic. I suppose something not to narrow angled.
I hope, that at least has helped a bit.
Kindly yours
Julien
--------
Music was my first love and it will be my last (John Miles)
======== FIND MY WEB-PROJECT AT: ========
http://ltsb.sourceforge.net
the Linux TextBased Studio guide
======= AND MY PERSONAL PAGES AT: =======
http://www.juliencoder.de
1:23 p.m.
On Fri, Jan 28, 2011 at 01:40:00AM -0500, Michal Seta wrote:
A friend of mine would like to record some impulse
response of various
spaces. I don't know the details nor the ultimate goal of this undertaking
but the problem was about the bst equipment for such recordings. I know a
loud signal is needed (she has a starter gun for that purpose) but unclear
about what kind of microphones should be used. Any tips? Ideas?
experiences?
Starter guns, electric sparks, exploding balloons or preservatives,
etc. are not the best way to do this. You get a much more accurate
result and a much better S/N ratio using a sine sweep and deconvolution
instead. Aliki (available on my website) can do this. See
<http://www.kokkinizita.net/papers/aliki.pdf> for an introduction.
The actual application does not have all the features explained in
the paper but it will do the basic IR measurement.
As for the microphones, this depends on the intended use of the
IR. For acoustic analysis you'd use a measurement mic, for reverb
whatever mic type provides the format you require.
Ciao,
--
FA
There are three of them, and Alleline.
6:16 p.m.
Em Fri, 28 Jan 2011 10:56:30 -0200
Fabio <capoeirista(a)arcor.de> escreveu:
Em Fri, 28 Jan 2011 13:23:06 +0100
fons(a)kokkinizita.net escreveu:
any answer on that one?
Aliki (available on my website) can do this.
I tried to install it form AUR in Arch but it depends on JAck-svn. is
this necessary?
6:28 p.m.
On Fri, Jan 28, 2011 at 03:16:31PM -0200, Fabio wrote:
It should work with any version of Jack that's not too old
(like more than a few years).
The dependency on jack-svn is wrong, I'd suggest you contact
the maintainer of the AUR package.
Ciao,
--
FA
There are three of them, and Alleline.
I tried to
install it form AUR in Arch but it depends on JAck-svn. is
this necessary?
any answer on that one?
7:58 p.m.
Em Fri, 28 Jan 2011 18:28:21 +0100
fons(a)kokkinizita.net escreveu:
On Fri, Jan 28, 2011 at 03:16:31PM -0200, Fabio
wrote:
It should work with any version of Jack that's not too old
(like more than a few years).
thanks
I tried
to install it form AUR in Arch but it depends on
JAck-svn. is this necessary?
any answer on that one?
The dependency on jack-svn is wrong, I'd suggest you contact
the maintainer of the AUR package.
done
3:37 p.m.
On Fri, 28 Jan 2011 13:23:06 +0100
fons(a)kokkinizita.net wrote:
On Fri, Jan 28, 2011 at 01:40:00AM -0500, Michal Seta
wrote:
question: why the amp/speakers don't have to be high quality
flat-response monitors (as I think Julien is saying), but the mic does?
Also, do mic vendors offer files with the frequency response of the mic
so one can "multiply the inverse of it" with the spectrum of the
signal recorded with said mic, taking mic charateristics out of the
equation (at least theoretically)?
Sorry if I'm baffling and confused, still trying to get a grip of this
IR - frequency response thing.
A friend of mine would like to record some
impulse response of
various spaces. I don't know the details nor the ultimate goal of
this undertaking but the problem was about the bst equipment for
such recordings. I know a loud signal is needed (she has a starter
gun for that purpose) but unclear about what kind of microphones
should be used. Any tips? Ideas? experiences?
Starter guns, electric sparks, exploding balloons or preservatives,
etc. are not the best way to do this. You get a much more accurate
result and a much better S/N ratio using a sine sweep and
deconvolution instead. Aliki (available on my website) can do this.
See <http://www.kokkinizita.net/papers/aliki.pdf> for an introduction.
The actual application does not have all the features explained in
the paper but it will do the basic IR measurement.
4:44 p.m.
On Fri, Jan 28, 2011 at 03:37:21PM +0100, Renato wrote:
fons(a)kokkinizita.net wrote:
They have to be of reasonable quality and FR, but any remaining
small errors can easily be calibrated out. You just take the
direct sound (for a good speaker + mic this will be the first few
ms of the IR) as a reference.
A few percent distortion (most speakers will have this) does not
matter if the measurement is done in the correct way: after the
deconvolution the distortion products will appear *before* the
real IR and they can be removed easily.
Starter guns, electric sparks, exploding balloons
or preservatives,
etc. are not the best way to do this. You get a much more accurate
result and a much better S/N ratio using a sine sweep and
deconvolution instead. Aliki (available on my website) can do this.
See <http://www.kokkinizita.net/papers/aliki.pdf> for an introduction.
The actual application does not have all the features explained in
the paper but it will do the basic IR measurement.
question: why the amp/speakers don't have to be high quality
flat-response monitors (as I think Julien is saying), but the mic does? Also, do mic vendors offer files with the frequency
response of the mic
so one can "multiply the inverse of it" with the spectrum of the
signal recorded with said mic, taking mic charateristics out of the
equation (at least theoretically)?
The high quality ones will have tight specs and usually come with
a measured FR or other calibration data.
There are a few other points to consider.
Most speakers will be directional at all but the lowest frequencies.
It depends on your application if this matters or not. If it does
(e.g. to measure room acoustics according to international standards)
you need an omnidirectional speaker. These are usually made as a
dodecahedron of small speakers. See <http://www.gizmag.com/go/3894>
for an example.
Also omni mics will have some directionality at high frequencies, and
that is why they come in two forms: calibrated for flat FR on-axis
(plane wave), or for flat FR in a diffuse field (averaged over all
directions). The difference matters only at very high frequencies.
Some measurement come with a small conical diffuser which can be
attached in front to improve diffuse-field response.
Ciao,
--
FA
There are three of them, and Alleline.
5:04 p.m.
On Fri, 28 Jan 2011 16:44:47 +0100
fons(a)kokkinizita.net wrote:
On Fri, Jan 28, 2011 at 03:37:21PM +0100, Renato
wrote:
Thanks for the detailed response; I realize this is still mostly
rocket-science for me and I'll have to study before asking further
explanations (I'll get there eventually).
renato
fons(a)kokkinizita.net wrote:
They have to be of reasonable quality and FR, but any remaining
small errors can easily be calibrated out. You just take the
direct sound (for a good speaker + mic this will be the first few
ms of the IR) as a reference.
A few percent distortion (most speakers will have this) does not
matter if the measurement is done in the correct way: after the
deconvolution the distortion products will appear *before* the
real IR and they can be removed easily.
Starter guns, electric sparks, exploding balloons
or
preservatives, etc. are not the best way to do this. You get a
much more accurate result and a much better S/N ratio using a
sine sweep and deconvolution instead. Aliki (available on my
website) can do this. See
<http://www.kokkinizita.net/papers/aliki.pdf> for an
introduction. The actual application does not have all the
features explained in the paper but it will do the basic IR
measurement.
question: why the amp/speakers don't have to be high quality
flat-response monitors (as I think Julien is saying), but the mic
does? Also, do mic vendors offer files with the
frequency response of the
mic so one can "multiply the inverse of it" with the spectrum of the
signal recorded with said mic, taking mic charateristics out of the
equation (at least theoretically)?
The high quality ones will have tight specs and usually come with
a measured FR or other calibration data.
There are a few other points to consider.
Most speakers will be directional at all but the lowest frequencies.
It depends on your application if this matters or not. If it does
(e.g. to measure room acoustics according to international standards)
you need an omnidirectional speaker. These are usually made as a
dodecahedron of small speakers. See <http://www.gizmag.com/go/3894>
for an example.
Also omni mics will have some directionality at high frequencies, and
that is why they come in two forms: calibrated for flat FR on-axis
(plane wave), or for flat FR in a diffuse field (averaged over all
directions). The difference matters only at very high frequencies.
Some measurement come with a small conical diffuser which can be
attached in front to improve diffuse-field response.
Ciao,
30 Jan
30 Jan
10:39 a.m.
OK, I read through the aliki docs, built aliki, and got it
running. I'm away from my audio room so I can't actually play
the sine sweeps, record the responses, etc.
I also read through 8 presentations by Farina, referenced in one
of the aliki documents. I've read 2-3 versions of the DRC docs
all the way through over the years.
I think I know how to get aliki to create an impulse response.
But, I'm unclear as to how to use that as an input for DRC
(digital room correction). I'm also unclear as to how to use
the impulse response to get at things like RT60, clarity and the
like. I *think* that if I could take the IR out of aliki and
bring it into octave, Maxima, or Matlab, that I could figure it
out from there. From the aliki docs it looks like exporting
of files outside it's initial format is planned, but not yet
implemented. Do I have this right?
Another thing I might want to do is to have a look at a time
plot including incident and reflected pulses. The time between
those should be an indicator of the total path length between
the source and the mic. By inspection of the acoustic space,
then I ought to be able to figure out about where reflections
are happening (thinking method of images) in that space and
apply sound treatments accordingly. At least, that's my wistful
hallucination. The pictures of impulse responses in the various
docs I looked at weren't zoomed in enough for me to really tell
what might be going on, and they were probably of real spaces,
and not simple textbook rectilinear polyhedrons. I wonder, is
aliki a tool that could help in this endeavor, if my idea is
worth attempting at all.
Aliki, and the direction it's going is quite exciting for me.
I'm definitely going to stay tuned to this channel.
Thanks for the nice work Fons!
--
Kevin
11:43 a.m.
On 01/30/2011 10:39 AM, Kevin Cosgrove wrote:
I think I know how to get aliki to create an impulse response.
But, I'm unclear as to how to use that as an input for DRC
(digital room correction).
just export wav files from aliki.
I'm also unclear as to how to use
the impulse response to get at things like RT60, clarity and the
like. I *think* that if I could take the IR out of aliki and
bring it into octave, Maxima, or Matlab, that I could figure it
out from there. From the aliki docs it looks like exporting
of files outside it's initial format is planned, but not yet
implemented. Do I have this right?
no. aliki does wav export just fine.
Another thing I might want to do is to have a look at
a time
plot including incident and reflected pulses. The time between
those should be an indicator of the total path length between
the source and the mic. By inspection of the acoustic space,
then I ought to be able to figure out about where reflections
are happening (thinking method of images) in that space and
apply sound treatments accordingly. At least, that's my wistful
hallucination.
no problem there.
The pictures of impulse responses in the various
docs I looked at weren't zoomed in enough for me to really tell
what might be going on, and they were probably of real spaces,
and not simple textbook rectilinear polyhedrons. I wonder, is
aliki a tool that could help in this endeavor, if my idea is
worth attempting at all.
it certainly is. what are you up to? first you mention doing DRC in
actual rooms, last paragraph seems to indicate you want to do some
theoretical stuff? simulations?
8:59 p.m.
On 30 January 2011 at 11:43, =?ISO-8859-1?Q?J=F6rn_Nettingsmeier?=
<nettings(a)folkwang-hochschule.de> wrote:
Fabulous.
Whew!
The task I'm starting to plan/attempt is to get my music room treated
and deal with the remaining artifacts with DRC. For a simple room,
e.g. 2 paths from source to listener, I should be able to see the
incident and 2nd path in the impulse response. In that case I can
identify the location of the reflection from the time delay and wall
location. In a more complicated room this might not be intuitive.
I was going to leave it there. But, it should be possible, once a
reflection is identified, to remove it from the impulse response
mathematically, leaving the other reflections, which would then show
up more clearly. I'm not planning to go down that road, just wanting
to understand.
Cheers....
--
Kevin
On 01/30/2011 10:39 AM, Kevin Cosgrove wrote:
Great.
I think I know how to get aliki to create an impulse response.
But, I'm unclear as to how to use that as an input for DRC
(digital room correction).
just export wav files from aliki. I'm also
unclear as to how to use
the impulse response to get at things like RT60, clarity and the
like. I *think* that if I could take the IR out of aliki and
bring it into octave, Maxima, or Matlab, that I could figure it
out from there. From the aliki docs it looks like exporting
of files outside it's initial format is planned, but not yet
implemented. Do I have this right?
no. aliki does wav export just fine. Another thing
I might want to do is to have a look at a time
plot including incident and reflected pulses. The time between
those should be an indicator of the total path length between
the source and the mic. By inspection of the acoustic space,
then I ought to be able to figure out about where reflections
are happening (thinking method of images) in that space and
apply sound treatments accordingly. At least, that's my wistful
hallucination.
no problem there. The pictures
of impulse responses in the various
docs I looked at weren't zoomed in enough for me to really tell
what might be going on, and they were probably of real spaces,
and not simple textbook rectilinear polyhedrons. I wonder, is
aliki a tool that could help in this endeavor, if my idea is
worth attempting at all.
it certainly is. what are you up to? first you mention doing DRC in
actual rooms, last paragraph seems to indicate you want to do some
theoretical stuff? simulations?
3:21 p.m.
New subject: Aliki update (was: OT - impulse response recording)
On Sun, Jan 30, 2011 at 01:39:23AM -0800, Kevin Cosgrove wrote:
OK, I read through the aliki docs, built aliki, and got it
running. I'm away from my audio room so I can't actually play
the sine sweeps, record the responses, etc.
...
Aliki can export WAV files, you can also zoom the IRs and do some
basic editing on them. The acoustic parameters are currently not
implemented.
There is a new release (0.1.0) as of today and the manual has
been updated as well.
Mainly bugfixes and small changes. The only visible one will
be the 'Output level' in the capture window.
Ciao,
--
FA
There are three of them, and Alleline.
9 p.m.
New subject: Aliki update (was: OT - impulse response recording)
On 30 January 2011 at 15:21, fons(a)kokkinizita.net wrote:
Aliki can export WAV files, you can also zoom the IRs
and do some
basic editing on them.
Fabulous.
The acoustic parameters are currently not
implemented.
OK.
There is a new release (0.1.0) as of today and the
manual has
been updated as well.
Just dld and built. Seems fine here on Mandriva 2010.2.
Mainly bugfixes and small changes. The only visible
one will
be the 'Output level' in the capture window.
OK.
Fons, would you like my RPM spec file or the source RPM?
Cheerio....
--
Kevin
9:34 p.m.
New subject: Aliki update (was: OT - impulse response recording)
On Sun, Jan 30, 2011 at 12:00:29PM -0800, Kevin Cosgrove wrote:
Fons, would you like my RPM spec file or the source
RPM?
I don't do any packaging or distribute packages for any distro,
it would really lead me too far. I guess the RPM based distros
have some place for packages contributed by users.
OTOH, if I can so something that makes packaging easier just
let me know. $DESTDIR was added to aliki's Makefile for that
reason for example.
Ciao,
--
FA
There are three of them, and Alleline.
11:16 p.m.
New subject: Aliki update (was: OT - impulse response recording)
On 30 January 2011 at 21:34, fons(a)kokkinizita.net wrote:
Completely understandable.
Fons, would
you like my RPM spec file or the source RPM?
I don't do any packaging or distribute packages for any distro,
it would really lead me too far. I guess the RPM based distros have some place for
packages
contributed by users.
Yes, Mandriva has a contribution mechanism. The hurdle has been
a little hard for me to try that thusfar. But, one day I should.
OTOH, if I can so something that makes packaging
easier just
let me know. $DESTDIR was added to aliki's Makefile for that
reason for example.
Your aliki tarball was _very_ easy to package.
Thanks!
--
Kevin
31 Jan
31 Jan
4:53 a.m.
On Fri, Jan 28, 2011 at 04:44:47PM +0100, fons(a)kokkinizita.net wrote:
On Fri, Jan 28, 2011 at 03:37:21PM +0100, Renato
wrote:
Really? So that little bit of mung before the "snap" in an IR is distortion, not
"predelay" or "early reflections" or any such thing? Wow, that's
good to know. I have to get busy and clean up some IR's then.
fons(a)kokkinizita.net wrote:
They have to be of reasonable quality and FR, but any remaining
small errors can easily be calibrated out. You just take the
direct sound (for a good speaker + mic this will be the first few
ms of the IR) as a reference.
A few percent distortion (most speakers will have this) does not
matter if the measurement is done in the correct way: after the
deconvolution the distortion products will appear *before* the
real IR and they can be removed easily. Starter guns, electric sparks, exploding balloons
or preservatives,
etc. are not the best way to do this. You get a much more accurate
result and a much better S/N ratio using a sine sweep and
deconvolution instead. Aliki (available on my website) can do this.
See <http://www.kokkinizita.net/papers/aliki.pdf> for an introduction.
The actual application does not have all the features explained in
the paper but it will do the basic IR measurement.
question: why the amp/speakers don't have to be high quality
flat-response monitors (as I think Julien is saying), but the mic does? Also, do mic vendors offer files with the
frequency response of the mic
so one can "multiply the inverse of it" with the spectrum of the
signal recorded with said mic, taking mic charateristics out of the
equation (at least theoretically)?
The high quality ones will have tight specs and usually come with
a measured FR or other calibration data.
There are a few other points to consider.
Most speakers will be directional at all but the lowest frequencies.
It depends on your application if this matters or not. If it does
(e.g. to measure room acoustics according to international standards)
you need an omnidirectional speaker. These are usually made as a
dodecahedron of small speakers. See <http://www.gizmag.com/go/3894>
for an example.
Also omni mics will have some directionality at high frequencies, and
that is why they come in two forms: calibrated for flat FR on-axis
(plane wave), or for flat FR in a diffuse field (averaged over all
directions). The difference matters only at very high frequencies.
Some measurement come with a small conical diffuser which can be
attached in front to improve diffuse-field response.
Ciao,
--
FA
There are three of them, and Alleline.
_______________________________________________
Linux-audio-user mailing list
Linux-audio-user(a)lists.linuxaudio.org
http://lists.linuxaudio.org/listinfo/linux-audio-user
12:01 p.m.
On Sun, Jan 30, 2011 at 07:53:18PM -0800, Ken Restivo wrote:
No, the little wobbles that can appear before the main impulse (which
is the direct 'dry' sound and should be removed anyway if the IR is
used for reverb) are not the distortion, but the result of
* the limited frequency range of the sweep (it usually doesn't start
at 0 Hz and stops before Fs/2),
* the imperfect FR of the speaker + mic.
The distorion appears much earlier.
Suppose you have log sweep going up in frequency by 1 octave per
second. If the speaker produces 2nd harmonic distortion, the
second harmonic will appear in its output 1 second before the
sweep reaches this frequency. The result after deconvolution is
a small 'impulse' 1 second before the main one. Usually you won't
even see it as the time range of the deconvolution is programmed
to start later.
In a similar way, the 3rd harmonic will appear 1.585 seconds early,
the 4th harmonic 2 seconds, etc.
Ciao,
--
FA
There are three of them, and Alleline.
On Fri, Jan 28, 2011 at 04:44:47PM +0100,
fons(a)kokkinizita.net wrote:
A few percent
distortion (most speakers will have this) does not
matter if the measurement is done in the correct way: after the
deconvolution the distortion products will appear *before* the
real IR and they can be removed easily.
Really? So that little bit of mung before the "snap" in an IR is
distortion, not "predelay" or "early reflections" or any such thing?
Wow, that's good to know. I have to get busy and clean up some IR's
then. 
30 Jan
30 Jan
11:34 a.m.
Am 28.01.2011 13:23, schrieb fons(a)kokkinizita.net:
On Fri, Jan 28, 2011 at 01:40:00AM -0500, Michal Seta
wrote:
This is true if you want perfectly exact, high fidelity, realistic
response-files of real rooms.
But if you just want files, that produce interesting sounding
reverb-effects, enything that fits, fits.
I use to record rooms using my mobile-phones puny videofunction, the
built-in micro and finger snapping ;-)
Not hi-fi at all and I would distribute these files claiming they would
be something like tools to reproduce the original rooms. But I like,
what I hear, if I load them into a convolver....
A friend of mine would like to record some
impulse response of various
spaces. I don't know the details nor the ultimate goal of this undertaking
but the problem was about the bst equipment for such recordings. I know a
loud signal is needed (she has a starter gun for that purpose) but unclear
about what kind of microphones should be used. Any tips? Ideas?
experiences?
Starter guns, electric sparks, exploding balloons or preservatives,
etc. are not the best way to do this. You get a much more accurate
result and a much better S/N ratio using a sine sweep and deconvolution
instead. Aliki (available on my website) can do this. See
<http://www.kokkinizita.net/papers/aliki.pdf> for an introduction.
The actual application does not have all the features explained in
the paper but it will do the basic IR measurement.
As for the microphones, this depends on the intended use of the
IR. For acoustic analysis you'd use a measurement mic, for reverb
whatever mic type provides the format you require.
Ciao,
1:11 p.m.
Am 30.01.2011 11:34, schrieb Hartmut Noack:
Am 28.01.2011 13:23, schrieb fons(a)kokkinizita.net:
Sorry for being too rash -- of course I would NOT...
On Fri, Jan 28, 2011 at 01:40:00AM -0500, Michal
Seta wrote:
This is true if you want perfectly exact, high fidelity, realistic
response-files of real rooms.
But if you just want files, that produce interesting sounding
reverb-effects, enything that fits, fits.
I use to record rooms using my mobile-phones puny videofunction, the
built-in micro and finger snapping ;-)
Not hi-fi at all and I would distribute these files claiming they would
be something like tools to reproduce the original rooms. A friend of mine would like to record some
impulse response of various
spaces. I don't know the details nor the ultimate goal of this
undertaking
but the problem was about the bst equipment for such recordings. I
know a
loud signal is needed (she has a starter gun for that purpose) but
unclear
about what kind of microphones should be used. Any tips? Ideas?
experiences?
Starter guns, electric sparks, exploding balloons or preservatives,
etc. are not the best way to do this. You get a much more accurate
result and a much better S/N ratio using a sine sweep and deconvolution
instead. But I like,
what I hear, if I load them into a convolver....
Aliki (available on my website) can do this. See
<http://www.kokkinizita.net/papers/aliki.pdf> for an introduction.
The actual application does not have all the features explained in
the paper but it will do the basic IR measurement.
As for the microphones, this depends on the intended use of the
IR. For acoustic analysis you'd use a measurement mic, for reverb
whatever mic type provides the format you require.
Ciao,
_______________________________________________
Linux-audio-user mailing list
Linux-audio-user(a)lists.linuxaudio.org
http://lists.linuxaudio.org/listinfo/linux-audio-user
1:22 p.m.
On Sunday 30 January 2011 11:34:31 Hartmut Noack wrote:
Am 28.01.2011 13:23, schrieb fons(a)kokkinizita.net:
Using a mobile phone to play the sinus-sweep and record it with a small mp3-
player should give you the ability to "measure" different source and target
positions in the acoustic space :-)
Gotta try that some day.
Have fun,
Arnold
On Fri, Jan 28, 2011 at 01:40:00AM -0500, Michal
Seta wrote:
This is true if you want perfectly exact, high fidelity, realistic
response-files of real rooms.
But if you just want files, that produce interesting sounding
reverb-effects, enything that fits, fits.
I use to record rooms using my mobile-phones puny videofunction, the
built-in micro and finger snapping ;-)
Not hi-fi at all and I would distribute these files claiming they would
be something like tools to reproduce the original rooms. But I like,
what I hear, if I load them into a convolver.... A friend of mine would like to record some
impulse response of various
spaces. I don't know the details nor the ultimate goal of this
undertaking but the problem was about the bst equipment for such
recordings. I know a loud signal is needed (she has a starter gun for
that purpose) but unclear about what kind of microphones should be
used. Any tips? Ideas? experiences?
Starter guns, electric sparks, exploding balloons or preservatives,
etc. are not the best way to do this. You get a much more accurate
result and a much better S/N ratio using a sine sweep and deconvolution
instead.
6:55 p.m.
Am 30.01.2011 13:22, schrieb Arnold Krille:
On Sunday 30 January 2011 11:34:31 Hartmut Noack
wrote:
I dont really believe in the built-in speakers. Especially if we talk
about frequencies below 150Hz ;-)
Am 28.01.2011 13:23, schrieb
fons(a)kokkinizita.net:
Using a mobile phone to play the sinus-sweep On Fri, Jan 28, 2011 at 01:40:00AM -0500, Michal
Seta wrote:
This is true if you want perfectly exact, high fidelity, realistic
response-files of real rooms.
But if you just want files, that produce interesting sounding
reverb-effects, enything that fits, fits.
I use to record rooms using my mobile-phones puny videofunction, the
built-in micro and finger snapping ;-)
Not hi-fi at all and I would distribute these files claiming they would
be something like tools to reproduce the original rooms. But I like,
what I hear, if I load them into a convolver.... A friend of mine would like to record some
impulse response of various
spaces. I don't know the details nor the ultimate goal of this
undertaking but the problem was about the bst equipment for such
recordings. I know a loud signal is needed (she has a starter gun for
that purpose) but unclear about what kind of microphones should be
used. Any tips? Ideas? experiences?
Starter guns, electric sparks, exploding balloons or preservatives,
etc. are not the best way to do this. You get a much more accurate
result and a much better S/N ratio using a sine sweep and deconvolution
instead. and record it with a small mp3-
player should give you the ability to "measure" different source and target
positions in the acoustic space :-)
Gotta try that some day.
I´d be very interested in such a usage-scenario. I got an old
Sharp-MD-recorder that came with a quite usable mini-mic...
Have fun,
Arnold
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8:29 p.m.
On Sun, Jan 30, 2011 at 06:55:18PM +0100, Hartmut Noack wrote:
A research assistant here did that last year - recorded his acoustic
measurement sweeps in mp3 format. Had to go back and do it all over
again... Whatever remains of a sweep after deconvolution is just junk.
As to the LF, many small devices such as mobile phones generate bass
by just exciting the miniature speaker at its resonance frequency.
Works well for kick drums etc. You get bass indeed, but nothing like
the original signal.
Ciao,
--
FA
There are three of them, and Alleline.
Am 30.01.2011 13:22, schrieb Arnold Krille:
Using a mobile
phone to play the sinus-sweep
I dont really believe in the built-in speakers. Especially if we
talk about frequencies below 150Hz ;-)
and record it with a small mp3-
player should give you the ability to "measure" different source and target
positions in the acoustic space :-)
Gotta try that some day.
I´d be very interested in such a usage-scenario. I got an old
Sharp-MD-recorder that came with a quite usable mini-mic...
9:27 p.m.
Am 30.01.2011 20:29, schrieb fons(a)kokkinizita.net:
On Sun, Jan 30, 2011 at 06:55:18PM +0100, Hartmut
Noack wrote:
A research assistant here did that last year - recorded his acoustic
measurement sweeps in mp3 format. Had to go back and do it all over
again... Whatever remains of a sweep after deconvolution is just junk.
Do you think, the same problem would arise with the MD-Recorder? ATRAC
is based on the same principles as MP3 so it may have the same
shortcomings when it comes to record material for HIFI-impulses.
Am 30.01.2011 13:22, schrieb Arnold Krille:
Using a
mobile phone to play the sinus-sweep
I dont really believe in the built-in speakers. Especially if we
talk about frequencies below 150Hz ;-)
and record it with a small mp3-
player should give you the ability to "measure" different source and target
positions in the acoustic space :-)
Gotta try that some day.
I´d be very interested in such a usage-scenario. I got an old
Sharp-MD-recorder that came with a quite usable mini-mic... As to the LF, many small devices such as mobile phones
generate bass
by just exciting the miniature speaker at its resonance frequency.
Works well for kick drums etc. You get bass indeed, but nothing like
the original signal.
I really would not think about trying something like this. Maybe if one
attaches a little amp and a 6"-speaker to the headphones-out but not
whith the builtin.
Anyway: I think it should either be low-end-punk (recording snaps with a
small multimedia-device) or the real thing with real speakers and real mics.
The low-end method comes with the benefit of being easily available in
any situation whithout spending much time and money for gear. If one
sacrifices these benefits to make some half-way a little better kind of
thing, the whole thing becomes pointless and should be abandoned in
favour of the Hi-end method I think.
Ciao,
9:41 p.m.
On Sun, Jan 30, 2011 at 09:27:46PM +0100, Hartmut Noack wrote:
Do you think, the same problem would arise with the
MD-Recorder?
ATRAC is based on the same principles as MP3 so it may have the
same shortcomings when it comes to record material for
HIFI-impulses.
Yes. Just imagine a reverb of 2 seconds (RT60), and a 10 seconds
long logarithmic sweep, that's about 1 second per octave. So
when the sweep is at 2 kHz, the room response for 1k kHz is
already 30 dB down. Any perceptual coding is going to remove
that, or make nonsense of it.
Ciao,
--
FA
There are three of them, and Alleline.
28 Jan
28 Jan
3:09 p.m.
On Friday 28 January 2011 07:40:00 Michal Seta wrote:
A friend of mine would like to record some impulse
response of various
spaces. I don't know the details nor the ultimate goal of this undertaking
but the problem was about the bst equipment for such recordings. I know a
loud signal is needed (she has a starter gun for that purpose) but unclear
about what kind of microphones should be used. Any tips? Ideas?
experiences?
Many have already suggested the use of a sinus-sweep.
For the mic: Sphere characteristics seem to have the best response. To be
safe, aim them towards the ground and therefor perpendicular or opposite to
the direction the reflections will come from. That way you avoid the near-field
effect which is highest from in front of the mic.
Last summer I did a quite'n'dirty impulse response from one of our hallways
here in university. Lots of blank concrete. Using just two blocks of wood gave
a reverb a bit nicer then the original because the higher frequencies where
attenuated in the bang itself.
but using a sinus-sweep will give you better results both for natural sounding
impulse responses and for measurement purpose impulse responses.
Have fun,
Arnold
4:18 p.m.
On Fri, Jan 28, 2011 at 03:09:14PM +0100, Arnold Krille wrote:
For the mic: Sphere characteristics seem to have the
best response. To be
safe, aim them towards the ground and therefor perpendicular or opposite to
the direction the reflections will come from. That way you avoid the near-field
effect which is highest from in front of the mic.
Omni ('sphere') mics don't have any near-field effect.
Ciao,
--
FA
There are three of them, and Alleline.
30 Jan
30 Jan
4:07 a.m.
On Fri, Jan 28, 2011 at 01:40:00AM -0500, Michal Seta wrote:
Hi all,
I know that there are some knowledgable people on this list, hence this OT
diversion.
A friend of mine would like to record some impulse response of various
spaces. I don't know the details nor the ultimate goal of this undertaking
but the problem was about the bst equipment for such recordings. I know a
loud signal is needed (she has a starter gun for that purpose) but unclear
about what kind of microphones should be used. Any tips? Ideas?
experiences?
Use Aliki and the best mics you can find.
-ken
5047
days inactive
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29 comments
10 participants
participants (10)
-
Arnold Krille -
Fabio -
fons＠kokkinizita.net -
Hartmut Noack -
Julien Claassen -
Jörn Nettingsmeier -
Ken Restivo -
Kevin Cosgrove -
Michal Seta -
Renato