Home |
Search |
Today's Posts |
#81
Posted to rec.audio.pro
|
|||
|
|||
Anyone heard of applying a sine wave to audio?
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 |
#82
Posted to rec.audio.pro
|
|||
|
|||
Anyone heard of applying a sine wave to audio?
"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. |
#83
Posted to rec.audio.pro
|
|||
|
|||
Anyone heard of applying a sine wave to audio?
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." |
#84
Posted to rec.audio.pro
|
|||
|
|||
Anyone heard of applying a sine wave to audio?
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 |
#85
Posted to rec.audio.pro
|
|||
|
|||
Anyone heard of applying a sine wave to audio?
"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. |
#86
Posted to rec.audio.pro
|
|||
|
|||
Anyone heard of applying a sine wave to audio?
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." |
#87
Posted to rec.audio.pro
|
|||
|
|||
Anyone heard of applying a sine wave to audio?
"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. |
#88
Posted to rec.audio.pro
|
|||
|
|||
Anyone heard of applying a sine wave to audio?
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." |
Reply |
Thread Tools | |
Display Modes | |
|
|