IPB

Welcome Guest ( Log In | Register )

Room measurements using pink noise
Yahzi
post Jan 15 2013, 11:54
Post #1





Group: Members
Posts: 209
Joined: 21-November 12
Member No.: 104669



I was browsing around and found this bit of information which I don't quite understand, so anyone who is well versed in acoustics can perhaps set a few things straight :

Accurate room measurement is complex in that you need.
1: A way to record what is going on in a room.
2: Away to create the sound in a room that 1 will measure.

Currently 1 is reasonably easy and cost effective to achieve as there are a number of accurate (or accurate enough) systems available that do much of the number crunching in software.

The most common way to achieve 2 is to use the loudspeakers already in the room and this while convenient, leads to inaccuracies in measurements.

The reasons for this are as follows.

To accurately excite all the modes in a room you need a source that is broadband and truly omnidirectional.
While most decent speakers can be broadband -but often are a little deficient at low frequencies-, few if any are truly omnidirectional.
This means that when using a speaker as an audio source in room measurement, you are in reality only measuring the combined response of your speaker and the room. The in room measurement of Bi or Di polar speakers that had the same frequency response would be totally different.

Ideally you want a sound source that as already mentioned is truly omnidirectional as this will excite all room modes equally. Any one who hasever looked at polar plots of speakers will know that even the best claimed omni speakers rarely are truly omnidirectional.

A gun shot on the other offers typically a wide bandwidth, is omnidirectional and has the added benefit of being loud. Loud enough so that true reverberation time and modal measurements can be made.

It has even been suggested, for those that don't want to fire their magnums in their listening rooms, that something as simple as a hand drill could be used as a sound source. These are cheap, the results are repeatable and will certainly put a lot less stress on a system than trying to belt out Pink noise at high SPL.


I thought pink noise was the standard method of measuring speakers in a room. He seems to be saying that a gunshot rather than pink noise is preferable as the levels are higher, or at least that's what I think he's saying. Is this guy completely on crack or does he have a point?
Go to the top of the page
+Quote Post
 
Start new topic
Replies
Yahzi
post Jan 16 2013, 10:16
Post #2





Group: Members
Posts: 209
Joined: 21-November 12
Member No.: 104669



Hi Ethan. So measuring the room on it's own is really just pointless? Because we don't hear just the room? I know with a gating measurement you can eliminate the room and "see" the raw speaker response. But how would you see the room response without the speaker affecting it? It sounds really silly, come to think of it.

This post has been edited by Yahzi: Jan 16 2013, 10:17
Go to the top of the page
+Quote Post
Arnold B. Kruege...
post Jan 16 2013, 14:08
Post #3





Group: Members
Posts: 4461
Joined: 29-October 08
From: USA, 48236
Member No.: 61311



QUOTE (Yahzi @ Jan 16 2013, 04:16) *
Hi Ethan. So measuring the room on it's own is really just pointless? Because we don't hear just the room? I know with a gating measurement you can eliminate the room and "see" the raw speaker response. But how would you see the room response without the speaker affecting it? It sounds really silly, come to think of it.


Measuring the room on its own is pointless for audio because that isn't how we use the room. Speakers are different enough from each other that they generally each cause the room to respond in a different way.

Reciprocally, the room has a very strong influence on the sound of the speaker, such that it is of questionable benefit to audition speakers in any room other than the one in which they are going to be used.
Go to the top of the page
+Quote Post

Posts in this topic


Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



RSS Lo-Fi Version Time is now: 20th December 2014 - 18:22