Hi All,
I'm doing my dissitation for my Bsc and need your help!!! I can't find any articals or refferance to the use of phase shift and delay to overcome bad acoustics..

I use a cardioide bass stack regulary and this is great for reducing the on stage bass. My therary is that you should be able to reducs the revrb (t60) time by firing phase shifted And possibably delayed signals into the reverbant area?

I dont think its as simple as that. Everything you did in the frequency domain would effect the time domain and vice versa which is why in recording circles Eq'ing a room to pink is frowned upon. You would need to use WFIR filters in DSP or something like that, or you resultant output would not be time aligned. Or are you talking about deliberately firing 180 deg phase shifts out to cancel reflections?

OK....

Here's my advice.

1) Buy a dictionary and learn to use it. No, really. If you have a hidden disability that affects your spelling and grammar, use spellcheckers and a text to speech programme.

2) Buy a good text book on electroacoustics. Read the section on room acoustics and the factors which affect RT60. I take it that you are trying to alter the level of the reverberant sound field? That may well be achievable (since it is influenced by source directivity) but this is very different from reducing the RT60.

3) Start looking in places that might actually have some answers, and which are peer reviewed. AES papers and papers from the IOA's Reproduced Sound conferences are a good starting point. I would not expect to see Wikipedia references, let alone chat room discussions in a final year degree dissertation.

Simon

There are some great text books out there that will explain the theory behind room acoustics.

I can understand that you were just looking for a bit of advice, but it's such a hugely complex subject that I'm not sure you'd get a clear and informative answer on a forum. I would suggest that the D&B electroacoustics seminars (which are free) are a fantastic start to understanding the basics of sound reproduction.

Good luck with your degree.

I'd suggest a) the Blue Room policy expects reasonable spelling and grammar, and b) whatever your take on the subject of 'spag', hopefully it should be commensurate with the level of the question asked. It appears the OP is at final year BSc level. I would expect clear communication from any student at that level.




I did suggest getting a textbook. I also suggested searching AES papers (which many Universities will have access to via Athens). IOA papers may be a little harder to get hold of, but there's still the Inter Library Loans service.

My reply may have been a little tart, but it was not intended as patronising - the OP seems to have some issues regarding the theory that underpins his project. Final year dissertations require a rigorous level of research and scholarly activity. Whereas forums and Wikis might be a possible starting point, few academics would accept such sources as cited references in a technical report.

Simon

OK All! That's enough comment on the OPs spelling. Point made, now move on please!

A couple of posts hidden or edited, sorry if you don't get a personal note, I should be working...

Agreed, the d&b Seminars are fantastic. I attended one in Cheltenham recently which was really really helpful in understanding room acoustics, and how incredibly complex they are (without making your head ache).

another vote for the usefulness and clarity of John Taylor's presentation. and they gave us a nice lunch and took us to the pub afterwards! (not sure wether this always happens - the one I went to was at their home base)

To echo Simon, the AES is always a good bet, but also check out JASA (again, most uni's will have access to it). Only point I would make is that conference papers are not peer reviewed, so don't hold them in as high a position as journal articles.

Are you trying to decrease the reverberation level, or the reverberation time?

The d&b seminars are very good, provide pertinent information, and do not degenerate into a blatant advertising event. John doesn't take the Electroacoustic seminars now, but the quality is still good (I was at the Cheltenham one too). The drinks afterwards are still part of the learning process! However, there's only so much that can be crammed into one day...

With regards to the discussion here, I would respectfully suggest that there seems to be some fundamental flaws with the OP's theory.

Simon