Reply
 
Thread Tools Display Modes
  #81   Report Post  
Posted to rec.audio.pro
Scott Dorsey Scott Dorsey is offline
external usenet poster
 
Posts: 16,853
Default 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   Report Post  
Posted to rec.audio.pro
hank alrich hank alrich is offline
external usenet poster
 
Posts: 4,736
Default 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   Report Post  
Posted to rec.audio.pro
Mark Mark is offline
external usenet poster
 
Posts: 966
Default 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   Report Post  
Posted to rec.audio.pro
Mike Rivers Mike Rivers is offline
external usenet poster
 
Posts: 8,744
Default 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   Report Post  
Posted to rec.audio.pro
Mike Rivers Mike Rivers is offline
external usenet poster
 
Posts: 8,744
Default 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   Report Post  
Posted to rec.audio.pro
hank alrich hank alrich is offline
external usenet poster
 
Posts: 4,736
Default 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   Report Post  
Posted to rec.audio.pro
Mxsmanic Mxsmanic is offline
external usenet poster
 
Posts: 805
Default 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

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Panoramic spectrum analysis DManzaluni High End Audio 47 April 2nd 09 09:41 PM
Software for sound spectrum analysis [email protected] Pro Audio 3 August 23rd 06 03:49 PM
Turntable Spectrum Analysis flatfish+++ Pro Audio 19 April 10th 04 02:07 PM
good web tutorial on spectrum analysis? BurningMoonGod Pro Audio 7 October 25th 03 06:54 PM
Spectrum Analysis in SF . hmm??? BESTnewEnglandDJ Pro Audio 2 July 15th 03 04:21 AM


All times are GMT +1. The time now is 05:27 PM.

Powered by: vBulletin
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AudioBanter.com.
The comments are property of their posters.
 

About Us

"It's about Audio and hi-fi"