Wanted: acoustic "noise" source - Page 2 - diyAudio
Go Back   Home > Forums > Design & Build > Equipment & Tools

Equipment & Tools From test equipment to hand tools

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 12th December 2011, 07:54 PM   #11
tvrgeek is offline tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
But was not their goal to be able to extract the room from the measurement?
  Reply With Quote
Old 12th December 2011, 10:37 PM   #12
dewardh is offline dewardh  United States
diyAudio Member
 
Join Date: Dec 2005
Location: Berkeley, CA
Quote:
Originally Posted by tvrgeek View Post
But was not their goal to be able to extract the room from the measurement?
What does that mean?

Their "goal" appears to have been to measure the power response of loudspeakers. Their proceedure (using the fan as a "flat" power source, and thus the "reference") also reveals the "reverberant room's" absorbtion curve, but I don't find any reference to that being a "goal", or to their using it to measure the absorbtion of other rooms. Which isn't to say that they didn't . . .
  Reply With Quote
Old 13th December 2011, 12:19 AM   #13
diyAudio Member
 
Chris Hornbeck's Avatar
 
Join Date: May 2011
Location: Little Rock
These days wouldn't it be easiest just to sum multiple mic locations from a small source? This also gets around the otherwise thorny issue of a single mic location's universality/validity.

Thanks,
Chris
  Reply With Quote
Old 13th December 2011, 12:48 AM   #14
diyAudio Member
 
Join Date: Mar 2007
Location: Canandaigua, NY USA
Wow, I have that same GR Sound & Vibration Analyzer with the coupling to the GR high speed chart recorder- they sold it as a system. Underneath is the beat frequency oscillator that could give 20-20k in one turn of the dial; got one of those too for heating the basement in the winter. It was neat gear and I used it to design several speakers, but the whole mess probably weighs a couple hundred pounds and can be replaced and far outclassed by a laptop and sound card. My lab is however, incomplete, as I've no squirrel cage fan.
__________________
May the root sum of the squares of the Forces be with you.

Last edited by Conrad Hoffman; 13th December 2011 at 12:50 AM.
  Reply With Quote
Old 13th December 2011, 12:57 AM   #15
diyAudio Member
 
Join Date: Mar 2010
This board is capable of being a very robust noise generator and has numerous other features. Plus, it has a 7 part article to go along with it that has been featured in Elektor magazine over the past 7 months.

Audio DSP Course (110001-91) - ELEKTOR.com | Electronics: Microcontrollers Embedded Audio Digital Analogue Test Measurement
  Reply With Quote
Old 13th December 2011, 01:40 AM   #16
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
How about a gun? You know, like a starter pistol - if it's the room that interests you and not the speaker. That's how a lot of impulse measurements of rooms are done.

That's what I wanted to do, until I found out you have to have a permit for a starter pistol in this stupid county.
  Reply With Quote
Old 13th December 2011, 04:22 AM   #17
dewardh is offline dewardh  United States
diyAudio Member
 
Join Date: Dec 2005
Location: Berkeley, CA
Quote:
Originally Posted by Chris Hornbeck View Post
These days wouldn't it be easiest just to sum multiple mic locations from a small source? This also gets around the otherwise thorny issue of a single mic location's universality/validity.
It would take a lot of locations, I suspect, and weighting the summation wouldn't be particularly easy. Of course the "fatal flaw" of all box loudspeakers (baffle step) is fairly simple to model, but how would you account for lobing (around the crossover frequency) on the forward vertical axis? The McIntosh technique actually measured the overall power respones . . .

For measuring a room it would probably be reasonable to take several measurements within the listening area, and to look selectively at absorption from particular walls or surfaces.
  Reply With Quote
Old 13th December 2011, 04:25 AM   #18
dewardh is offline dewardh  United States
diyAudio Member
 
Join Date: Dec 2005
Location: Berkeley, CA
Quote:
Originally Posted by Conrad Hoffman View Post
My lab is however, incomplete, as I've no squirrel cage fan.
As is mine <g>. The electronics is all easily replaced (and improved on) with more "modern" equipment . . . but without an acoustic source for reference and calibration . . .
  Reply With Quote
Old 13th December 2011, 04:30 AM   #19
dewardh is offline dewardh  United States
diyAudio Member
 
Join Date: Dec 2005
Location: Berkeley, CA
Quote:
Originally Posted by maxseeley View Post
This board is capable of being a very robust noise generator[/url]
There is no shortage of electronic pink noise sources, the problem is getting from that to "flat" acoustic noise (rather than the non-flat "power response" of almost all loudspeakers).

I'm looking for a flat (or accurately defined) acoustic source . . .
  Reply With Quote
Old 13th December 2011, 04:39 AM   #20
dewardh is offline dewardh  United States
diyAudio Member
 
Join Date: Dec 2005
Location: Berkeley, CA
Quote:
Originally Posted by Pano View Post
How about a gun? You know, like a starter pistol - if it's the room that interests you and not the speaker.
That is, of course, the old "standard source" for reverberation time . . . but I've never seen it characterized for power distribution in a way that would make it easily used for absorbtion profile. And there is that "problem" you mention . . . you probably wouldn't be allowed to carry a fan onto an airplane (they'd find a reason), but it probably wouldn't be an issue in the studio or performance space (or my listening room <g> . . .). And a steady-state noise source is easy to measure and visualize (with a spectrum analyzer).
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Blu Ray BD Disc "In Concert" resp "live at" - Overview wanted tiefbassuebertr Music 2 5th January 2012 02:54 PM
31 Band Equalizer "the t.eq" "TQ-60" schematic wanted tiefbassuebertr Solid State 2 29th March 2010 03:45 PM
Wanted to Buy: Pairs of 5-1/2";6-1/2";8";10" Seas Aluminum Woofers dtm1962 Swap Meet 0 15th January 2010 04:38 PM
A "Standard Noise Source" for SPL meters. Jonathan Bright Everything Else 6 13th July 2004 10:19 PM


New To Site? Need Help?

All times are GMT. The time now is 06:42 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2