How can I get rid of metallic ring

[roadsweeper]

We have just finished construction of a new live room dedicated to vocals/acoustic instruments. It has all been soundproofed with various layers of wall, soundproof matting etc. Today I fitted all of the acoustic foam which covers approximately 60% of all wall surfaces. However, although the reverb time is almost perfect, there is still a strange metallic ring which can be heard. Thought that it might be the metal lampshades but have taken them off and we still get it. Although we still have some more treatment to put on the ceiling I am still worried about the sound. It is a frequency of around 2 - 5k and takes almost 1 second to decay. Does anyone have any ideas? Maybe we need to think more about diffusion?

[avare]

You know, details would be nice. Size, shape, location of treatment, etc. My first guess is that you are experiencing flutter echo. This is caused by sound going back and forth between two parallel surfaces. If you do have such a situation, then either diffusion, or moving absorbent material so that parallel surfaces have absorption on one of the surfaces will correct it.

Andre

[Weasel9992]

Originally Posted by avare

You know, details would be nice. Size, shape, location of treatment, etc. My first guess is that you are experiencing flutter echo. This is caused by sound going back and forth between two parallel surfaces. If you do have such a situation, then either diffusion, or moving absorbent material so that parallel surfaces have absorption on one of the surfaces will correct it.

Andre

+1. Totally agree with Andre as usual. Room details would be great.

Frank

[roadsweeper]

yes, sorry I should have included details! The room is approximately 4.8 metres in length, 3 metres wide and the ceiling is 2.2 metres high. All walls are pretty much parallel, however 2 of the walls are irregular brick whereas the other 2 are plasterboard. The ceiling is also plasterboard. One wall has a 4 foot by 4 foot window through to the control room. The acoustic treatment is spread equally across the four walls and as I mentioned before, the ceiling will have treatment on it shortly. The floor is wooden although we will be carpeting it shortly. I think that you may be right about the flutter as the ceiling and floor are parallel and untreated.Thanks for the help so far.

[Weasel9992]

The floor and ceiling would be my first guess at this point. See what happens after you install the carpet.

Frank