Jump to content


Need some sound 101 Advice about Pink Noise

Pink Noise Problem

  • Please log in to reply
7 replies to this topic

#1 Crowndog

Crowndog

    Power User

  • Members
  • PipPipPipPipPip
  • 23 posts

Posted 26 February 2013 - 08:26 PM

I need some help with the topic of Pink noise from the collective here. Please help me with this issue as it is getting more confusing the more I look into it.
I am Eq-ing my room. I have at my command a Crown RTA-2 and a digital RTA. Both have Pink noise sources. I also just refurbed all the filters in the RTA-2 by replacing the known to go bad tantalum caps and the electrolytics. I have the EQ2 equalizer and the digital RTA has a digital 31 band 2 channel equalizer as well.
I bought a dongle type device that has microphone balanced output of Pink noise which I was going to use to calibrate the RTA-2 filters. I checked it's output and it is sloped 3db/octave. All the other Pink noise sources are flat. Now I know that Pink noise is white noise that has been filtered with a 3db/octave filter but has equal spectral power across the spectrum. So should the output of a Pink Noise source be flat or sloped? The Crown RTA-2 Pink noise is flat in the manual graph and on the digital RTA. and on the Crown RTA-2 it's self. The digital RTA Pink Noise source is flat on it's own RTA and on the Crown RTA-2. The dongle is sloped on both.
I think the device is wrong. The creator/manufacturer insists it is correct. Help! what is going on here?

#2 bobbysdad

bobbysdad

    Power User

  • Members
  • PipPipPipPipPip
  • 38 posts

Posted 26 February 2013 - 09:16 PM

You're right....  :)
I might be deaf, but I can still hear the bells......

#3 dakos

dakos

    Admin

  • Members
  • PipPipPipPipPip
  • 744 posts

Posted 28 February 2013 - 01:10 AM

I would say the dongle is simply wrong. You have two extreamly professional devices that were pretty expensive back in their day, if I had to guess which device was accurate my money was on the two RTAs. If you have an iPhone/iPad and want to check what's going on using yet another device, there are plenty of free RTA apps on the App Store, they are not as accurate but give a pretty good idea of what's going on. There are also free noise generators apps if you need them :)
Avi

#4 bobbysdad

bobbysdad

    Power User

  • Members
  • PipPipPipPipPip
  • 38 posts

Posted 28 February 2013 - 05:19 AM

To quote:

View Postdakos, on 28 February 2013 - 01:10 AM, said:

You have two extreamly professional devices that were pretty expensive back in their day, if I had to guess which device was accurate my money was on the two RTAs.  :)
Avi

My sentiments exactly.

Have fun....   :)
I might be deaf, but I can still hear the bells......

#5 joust

joust

    Power User

  • Members
  • PipPipPipPipPip
  • 453 posts

Posted 04 March 2013 - 04:21 PM

Just a thought: Have you 'acoustically' treated your room previously? Of course it's all nice and dandy if you could EQ the room, but what about the extraneous reverberation signals that might affect the RTA?

#6 Crowndog

Crowndog

    Power User

  • Members
  • PipPipPipPipPip
  • 23 posts

Posted 25 March 2013 - 06:50 AM

Thank you for the replies. Since posting on sites globally I have heard back the same comments regarding this dongle device. I did learn that there are two different (possibly more) types of RTA's.  "Constant percentage bandwidth" RTAs and "constant bandwidth" RTAs. Pink noise will appear flat on one and  sloped on the other. However the consensus is that the Dongle device while a wonderful idea is not correct for the vast majority of RTAs  that are in use today. White noise should appear sloped on my RTAs because they are "Constant percentage bandwidth" type RTAs and Pink noise should appear flat.

If anyone feels that this is not correct please update this information! And again I thank the collective here.

#7 Crowndog

Crowndog

    Power User

  • Members
  • PipPipPipPipPip
  • 23 posts

Posted 25 March 2013 - 07:00 AM

View Postjoust, on 04 March 2013 - 04:21 PM, said:

Just a thought: Have you 'acoustically' treated your room previously? Of course it's all nice and dandy if you could EQ the room, but what about the extraneous reverberation signals that might affect the RTA?

I have been using spectral analysis to equalize my listening room for over 30 years. In the early days I used our hardwired TTL research computer at graduate school to do real time FFTs and using a ADS Soundshaper equalizer flattened the room response. As electronics got smaller and less expensive I used dedicated RTA's. The art IMHO of using this at home is finding acoustic room treatment that doesn't look like acoustic treatment i.e. tiles,baffles etc. Instead I use floor coverings, tapestries, furniture etc. in order to create a sound friendly room. I must say that the effort has paid off. One of my favorite tests is to compare a live instrument say a violin or piano to my system in a A B comparison. Blindfolded I have spoofed many "ears". To me that is the acid test, when instruments sound like the real thing.

#8 Crowndog

Crowndog

    Power User

  • Members
  • PipPipPipPipPip
  • 23 posts

Posted 25 March 2013 - 08:11 AM

pic