Home |
Search |
Today's Posts |
#81
Posted to rec.audio.pro
|
|||
|
|||
Getting accurate sound levels in spectrum analysis
Mxsmanic wrote:
Mike Rivers writes: The frequency may be the same, but not all transformers are the same. It's not the sweep that makes the noise, it's all the things rattle around that aren't supposed to be transducer. But they should all rattle at the same frequency, since the sync frequency is locked. Sadly, the fundamental is, but nothing else is. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#82
Posted to rec.audio.pro
|
|||
|
|||
Getting accurate sound levels in spectrum analysis
Frank Stearns wrote:
Mike Rivers writes: On 2/9/2012 8:41 PM, Mxsmanic wrote: If you know it's actually from a CRT, couldn't you superimpose a signal of exactly the same frequency and opposite phase and remove it Actually, I have a better answer than what I just posted. If you have a sample of the noise that's fairly well isolated, there are "noise cancellation" programs that, in a more sophisticated version of what you propose, do what you're dreaming about. They work by analyzing the spectrum of the sample of the noise that you want to remove and subtracting that from the program material. It can work fairly well for Mike, have you run across a particular package that does this really well? I've got a couple different venues that have some specific noise spectra between 90 and 110 hz. (I know; weird frequency range. Seems to be some sort of "blow across the coke bottle" resonance in the air returns which appear to be too small for the volume of the halls. In one hall you can stand about four feet from one of the two returns, release a piece of paper from chest height, and it quickly sails to the grill and smack, becomes a prisoner.) I've messed with the periodic noise removal tool in sound forge and it seems completely useless for this. (And I have recorded some nice samples of this noise when it was just me in the hall. Even though it sounds like periodic noise, perhaps it's too chaotic? The analyzer shows a fair amount of random bouncing at that hz range; turbulance in the resonate cavity of the return shaft, no doubt.) Be curious to hear any product recommendations you might have. Maybe there's a really smart one that could keep adjusting itself to variations in the noise spectra. iZotope RX is alleged to be quite powerful for noise removal. www.izotope.com/rx/ -- shut up and play your guitar * http://hankalrich.com/ http://www.youtube.com/walkinaymusic http://www.sonicbids.com/HankandShaidri |
#83
Posted to rec.audio.pro
|
|||
|
|||
Getting accurate sound levels in spectrum analysis
The frequency may be the same, but not all transformers are the same. It's not the sweep that makes the noise, it's all the things rattle around that aren't supposed to be transducer. But they should all rattle at the same frequency, since the sync frequency is locked. true, but... In order to "cancel" it out, you need to match both the amplitude and phase. by the time the acoustical signal travels to your mic and gets into your recorder after bouncing around in the room, the amplitude and phase will be essentially random. If there is any movement in the room, the amplitude and phase will change. Some burglar systems use this principal in fact. If you are looking for something educational to do, take a mic and hook it up to your computer and run a real time analyzer and observe various sounds. It is surprising how well you can see the H sync from a TV even in the next room, but it is far from stable. A Notch filter will work well. Cancellation is all but impossible without some kind of real time phase and amplitude tracking loop. This program is very educational... http://www.qsl.net/dl4yhf/spectra1.html have fun Mark |
#84
Posted to rec.audio.pro
|
|||
|
|||
Getting accurate sound levels in spectrum analysis
On 2/10/2012 7:21 PM, Mxsmanic wrote:
Mike Rivers writes: Why would your equipment be exaggerating a particular frequency range? I don't know. Maybe it's not perfect. Well, of course it's not perfect, but if it's exaggerating a particular frequency range enough to be bothersome to a reasonable listener, or even to a critical listener, it's either unsuitable for the job or it's broken. You shouldn't be using it. Well, I upload things to YouTube, but I don't get much feedback, especially on the audio (but the audio is usually just ambient noise). Well, I'm not at all surprised that you're not getting any comments. With something like that, only you know what it really sounded like, and unless it's really interesting, probably nobody else cares. -- "Today's production equipment is IT based and cannot be operated without a passing knowledge of computing, although it seems that it can be operated without a passing knowledge of audio." - John Watkinson http://mikeriversaudio.wordpress.com - useful and interesting audio stuff |
#85
Posted to rec.audio.pro
|
|||
|
|||
Getting accurate sound levels in spectrum analysis
On 2/10/2012 6:36 PM, Mxsmanic wrote:
Mike Rivers writes: The frequency may be the same, but not all transformers are the same. It's not the sweep that makes the noise, it's all the things rattle around that aren't supposed to be transducer. But they should all rattle at the same frequency, since the sync frequency is locked. I give up, since you won't seem to. But I'm right about this and you're just guessing and arguing. -- "Today's production equipment is IT based and cannot be operated without a passing knowledge of computing, although it seems that it can be operated without a passing knowledge of audio." - John Watkinson http://mikeriversaudio.wordpress.com - useful and interesting audio stuff |
#86
Posted to rec.audio.pro
|
|||
|
|||
Getting accurate sound levels in spectrum analysis
Mike Rivers wrote:
On 2/10/2012 6:36 PM, Mxsmanic wrote: Mike Rivers writes: The frequency may be the same, but not all transformers are the same. It's not the sweep that makes the noise, it's all the things rattle around that aren't supposed to be transducer. But they should all rattle at the same frequency, since the sync frequency is locked. I give up, since you won't seem to. But I'm right about this and you're just guessing and arguing. He could use a grasp of the concept that what is generated at the source will differ from what is received and that several variables will affect what is received. -- shut up and play your guitar * http://hankalrich.com/ http://www.youtube.com/walkinaymusic http://www.sonicbids.com/HankandShaidri |
#87
Posted to rec.audio.pro
|
|||
|
|||
Getting accurate sound levels in spectrum analysis
Mike Rivers writes:
Well, I'm not at all surprised that you're not getting any comments. With something like that, only you know what it really sounded like, and unless it's really interesting, probably nobody else cares. True. A few people have mentioned that they prefer the videos without music (all but two have no music), which rather surprised me, but that's fine with me, since it costs money to license background music. |
Reply |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Panoramic spectrum analysis | High End Audio | |||
Software for sound spectrum analysis | Pro Audio | |||
Turntable Spectrum Analysis | Pro Audio | |||
good web tutorial on spectrum analysis? | Pro Audio | |||
Spectrum Analysis in SF . hmm??? | Pro Audio |