[Don Pearce[_3_]]

On Sun, 8 Jun 2014 12:54:48 -0400, "None" wrote:

"Don Pearce" wrote in message
...
On Sun, 8 Jun 2014 08:50:56 -0500, "Neil Gould"
wrote:

docsavage20 wrote:
I heard someone talk about applying a sine wave to audio as some
kind
of mastering tweak. I've never heard of this, is this a
term/technique you're familiar with? If so how does it work?

The closest thing that I can come up with is the use of a sine wave
sweep to
sample the acoustics of an environment to create an impuse response
(IR)
reverb image of that environment. That result is applied as a
convolution
"map" in an IR utility, rather than as a sine wave applied directly
to the
audio. Such utilities are included with some DAWs, and/or are
available as
stand-alone plug-ins, and the logical time to use it would be during
final
mixing or mastering.

Huh? You create an impulse response with an impulse - something like
an old fashioned kids' cap gun. Or if you want better accuracy, a
loud
electric spark discharge.

Of if you want even better accuracy, use a swept sine wave to measure
the frequency response, and then use an FFT to derive the impulse
response. That's the way we usually do it around here. I don't know
anyone who uses a spark to measure rooms any more. It's even falling
out of favor for measuring microphones.


The problem with the swept sine method is that you need a transducer
to generate it, and that transducer has its own response. I know it is
a convenient method and doesn't make startling bangs, but it does have
these limitations not possessed by the normal impulse method. A spark
discharge has a guaranteed spectrum in the audio band.

d

[None]

"Don Pearce" wrote in message
...
On Sun, 8 Jun 2014 12:54:48 -0400, "None" wrote:

"Don Pearce" wrote in message
...
On Sun, 8 Jun 2014 08:50:56 -0500, "Neil Gould"
wrote:

docsavage20 wrote:
I heard someone talk about applying a sine wave to audio as some
kind
of mastering tweak. I've never heard of this, is this a
term/technique you're familiar with? If so how does it work?

The closest thing that I can come up with is the use of a sine
wave
sweep to
sample the acoustics of an environment to create an impuse
response
(IR)
reverb image of that environment. That result is applied as a
convolution
"map" in an IR utility, rather than as a sine wave applied
directly
to the
audio. Such utilities are included with some DAWs, and/or are
available as
stand-alone plug-ins, and the logical time to use it would be
during
final
mixing or mastering.

Huh? You create an impulse response with an impulse - something
like
an old fashioned kids' cap gun. Or if you want better accuracy, a
loud
electric spark discharge.

Of if you want even better accuracy, use a swept sine wave to
measure
the frequency response, and then use an FFT to derive the impulse
response. That's the way we usually do it around here. I don't know
anyone who uses a spark to measure rooms any more. It's even falling
out of favor for measuring microphones.


The problem with the swept sine method is that you need a transducer
to generate it, and that transducer has its own response. I know it
is
a convenient method and doesn't make startling bangs, but it does
have
these limitations not possessed by the normal impulse method. A
spark
discharge has a guaranteed spectrum in the audio band.

A spark is nowhere near as perfect as all that. There is no such
guarantee.

Some of the problems with the speaker method can be mitigated. For
instance, we take a nearfield measurement of the speaker
simultaneously, which can be used to calculate a transfer function
rather than a spectrum, or to be used as a correction to the spectrum.
The very short duration of a spark means there is very little radiated
acoustic energy, especially when long acquisition times are used for
large rooms. You get much better S/N with a swept sine. No practicable
method is perfect.

[Scott Dorsey]

None wrote:

Huh? You create an impulse response with an impulse - something like
an old fashioned kids' cap gun. Or if you want better accuracy, a
loud
electric spark discharge.

Of if you want even better accuracy, use a swept sine wave to measure
the frequency response, and then use an FFT to derive the impulse
response. That's the way we usually do it around here. I don't know
anyone who uses a spark to measure rooms any more. It's even falling
out of favor for measuring microphones.

The problem with swept sine method is that you now need a perfectly
omnidirectional and perfectly flat response sine wave source.

The problem with the impulse excitation method is that you need a
perfectly omnidirectional and perfectly shaped impulse.

I tend to be a fan of the impulse source method myself, although these
days a lot of people are using MLS stuff as a third method.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Neil[_9_]]

On 6/8/2014 1:44 PM, Don Pearce wrote:
On Sun, 8 Jun 2014 12:54:48 -0400, "None" wrote:

"Don Pearce" wrote in message
...
On Sun, 8 Jun 2014 08:50:56 -0500, "Neil Gould"
wrote:

docsavage20 wrote:
I heard someone talk about applying a sine wave to audio as some
kind
of mastering tweak. I've never heard of this, is this a
term/technique you're familiar with? If so how does it work?

The closest thing that I can come up with is the use of a sine wave
sweep to
sample the acoustics of an environment to create an impuse response
(IR)
reverb image of that environment. That result is applied as a
convolution
"map" in an IR utility, rather than as a sine wave applied directly
to the
audio. Such utilities are included with some DAWs, and/or are
available as
stand-alone plug-ins, and the logical time to use it would be during
final
mixing or mastering.

Huh? You create an impulse response with an impulse - something like
an old fashioned kids' cap gun. Or if you want better accuracy, a
loud
electric spark discharge.

Of if you want even better accuracy, use a swept sine wave to measure
the frequency response, and then use an FFT to derive the impulse
response. That's the way we usually do it around here. I don't know
anyone who uses a spark to measure rooms any more. It's even falling
out of favor for measuring microphones.


The problem with the swept sine method is that you need a transducer
to generate it, and that transducer has its own response. I know it is
a convenient method and doesn't make startling bangs, but it does have
these limitations not possessed by the normal impulse method. A spark
discharge has a guaranteed spectrum in the audio band.

There benefits and limitations correlated with any method. As I see it,
the issue is not so much the fact that such imperfections exist, but how
to best work with the results. In the bigger picture, they typically
won't be the weakest spot in a production.
--
best regards,
Neil

[William Sommerwerck]

"Scott Dorsey" wrote in message ...

The problem with swept sine method is that you now need a perfectly
omnidirectional and perfectly flat response sine wave source.
The problem with the impulse excitation method is that you need
a perfectly omnidirectional and perfectly shaped impulse.

Actually, the real problem is that the impulse response is necessarily
different from each instrument or performer. What arrives at the mic is a
summation of these different responses. This means that the deconvolution will
necessary be an approximation.

[Scott Dorsey]

William Sommerwerck wrote:
"Scott Dorsey" wrote in message ...

The problem with swept sine method is that you now need a perfectly
omnidirectional and perfectly flat response sine wave source.
The problem with the impulse excitation method is that you need
a perfectly omnidirectional and perfectly shaped impulse.

Actually, the real problem is that the impulse response is necessarily
different from each instrument or performer. What arrives at the mic is a
summation of these different responses. This means that the deconvolution will
necessary be an approximation.

That's a different problem and it's the same no matter WHAT method you use
to record it.

In addition, of course, there are plenty of things you will want to use the
impulse response for directly that have nothing to do with deconvolution.
You might, for instance, want to use it looking for flutter echoes or
spurious room reflections or other acoustical analysis.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[William Sommerwerck]

"Scott Dorsey" wrote in message ...
William Sommerwerck wrote:
"Scott Dorsey" wrote in message ...

The problem with the swept-sine method is that you now need
a perfectly omnidirectional and perfectly flat response sine wave
source. The problem with the impulse excitation method is that
you need a perfectly omnidirectional and perfectly shaped impulse.

Actually, the real problem is that the impulse response is necessarily
different from each instrument or performer. What arrives at the mic
is a summation of these different responses. This means that the
deconvolution will necessarily be an approximation.

That's a different problem and it's the same no matter WHAT
method you use to record it.

My point is that it's more-significant than the technique you use to
measure/compute the impulse response.

[Scott Dorsey]

William Sommerwerck wrote:
"Scott Dorsey" wrote in message ...
William Sommerwerck wrote:
"Scott Dorsey" wrote in message ...

The problem with the swept-sine method is that you now need
a perfectly omnidirectional and perfectly flat response sine wave
source. The problem with the impulse excitation method is that
you need a perfectly omnidirectional and perfectly shaped impulse.

Actually, the real problem is that the impulse response is necessarily
different from each instrument or performer. What arrives at the mic
is a summation of these different responses. This means that the
deconvolution will necessarily be an approximation.

That's a different problem and it's the same no matter WHAT
method you use to record it.

My point is that it's more-significant than the technique you use to
measure/compute the impulse response.

If in fact you're using it to generate artificial room reverb, then this is
the case. But if you're using the impulse for distance measurement purposes,
for instance, it might not be.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."