niall Posted April 3, 2008 Share Posted April 3, 2008 Today's metro carries the following story (Page 9 in the Scottish version) in their MiniCosm section Sounds Good:The days of ear-shattering feedback at concerts could be numbered thanks to a new piece of software. Feedback occurs when a frequency reaches a critical volume and is captured by microphones and sent to the speakers, then picked up and re-amplified. The software, created by University of London researchers, lowers a frequency when it rises above its critical volume and prevents feedback, reported New Scientist. so have they never heard of this, or am I missing something?! Link to comment Share on other sites More sharing options...
Solstace Posted April 3, 2008 Share Posted April 3, 2008 Yeah I thought that too, but then the pedant in me saw this bit: snip... ...lowers a frequency when it rises above its critical volume... ...snip So a feedback ring starts in your gig at 1KHz let's say, rises above its critical volume, then gets lowered to say, 500Hz? Or lower still if it persists? As my GF pointed out when she forwarded me this story by text earlier today: "Bet that could be annoying to work with at first..." :( Link to comment Share on other sites More sharing options...
Ynot Posted April 3, 2008 Share Posted April 3, 2008 So a feedback ring starts in your gig at 1KHz let's say, rises above its critical volume, then gets lowered to say, 500Hz? Or lower still if it persists?I seriously doubt that...Firstly I'd hazard a guess that trying to change the FREQUENCY of an offending feedback loop would be pretty darned tricky, and secondly WTF would it do to the actual musical content...???? No - I susoect that the statement means that it simply lowers the level of the howling frequency. But that's not news - there are a couple of FB eliminators on the market that do just that...The Sabine FBX for one... Link to comment Share on other sites More sharing options...
Simon Lewis Posted April 3, 2008 Share Posted April 3, 2008 There are feedback reducers that do introduce a frequency shift... which can generate some nasty side effects. It's usuable for speech, perhaps not so much for music ;-) Link to comment Share on other sites More sharing options...
MarkPAman Posted April 3, 2008 Share Posted April 3, 2008 Same story in The Guardian, I think. Link to comment Share on other sites More sharing options...
paulears Posted April 3, 2008 Share Posted April 3, 2008 Back in the 70s we had a device that introduced a pitch shift - memory is telling me it was very small - about 5Hz, but comment at the time agreed with the speech only, or very odd sound - however, now we DSP, take a ringing frequency, and instead of notching it, just shift that part - leaving the rest. The shift would reduce or cut the feedback, but leave the majority of the sound intact. This could have legs? Link to comment Share on other sites More sharing options...
Arran Posted April 3, 2008 Share Posted April 3, 2008 Back in the 70s we had a device that introduced a pitch shift - memory is telling me it was very small - about 5Hz, but comment at the time agreed with the speech only, or very odd sound - however, now we DSP, take a ringing frequency, and instead of notching it, just shift that part - leaving the rest. The shift would reduce or cut the feedback, but leave the majority of the sound intact. This could have legs? But if you shift the freq' it'll sum with the content of the freq' it's shifted to, creating an abnormal amount of energy at that freq' and causing more feedback?I suspect it might have been a slow news day and next week's Metro may feature The wheel, or maybe fire. Link to comment Share on other sites More sharing options...
charlyfarly Posted April 3, 2008 Share Posted April 3, 2008 These devices are old news to the likes of us but to "Joe Schmow" it's being let into a side of the Dark Art of what can be used in event audio. :( Link to comment Share on other sites More sharing options...
Solstace Posted April 3, 2008 Share Posted April 3, 2008 No - I susoect that the statement means that it simply lowers the level of the howling frequency. That's kinda what I was getting at... Sorry folks - it was evidently harder to get my humour right in this one than I thought... Back in serious mode - when I thought about it some more, I figured a slight pitch shift might have the desired effect, but like some others here I would think this risks highlighting the feedback by adding extra audible effects to get rid of it, or perhaps even risks feedback by exciting other problematic frequencies... Nice to see the boffins work on this though! :( Link to comment Share on other sites More sharing options...
Ynot Posted April 3, 2008 Share Posted April 3, 2008 Back in the 70s we had a device that introduced a pitch shift - memory is telling me it was very small - about 5Hz,But reading the Grauniad article linked above shows that it's NOT a pitch shift option at all...Reiss told New Scientist magazine that his software works differently. During the sound check the engineer identifies levels of various frequencies that will trigger feedback. During the gig if these frequencies approach their maximum then the software tweaks the master volume so that feedback never happens. Link to comment Share on other sites More sharing options...
MarkPAman Posted April 3, 2008 Share Posted April 3, 2008 During the sound check the engineer identifies levels of various frequencies that will trigger feedback. During the gig if these frequencies approach their maximum then the software tweaks the master volume so that feedback never happens. So it's a compressor with some narrow band filters on the side chain. Link to comment Share on other sites More sharing options...
ShaneBryan Posted April 3, 2008 Share Posted April 3, 2008 So something like the Behringer DEQ2496? Which would do more than this. Link to comment Share on other sites More sharing options...
Rob_Beech Posted April 3, 2008 Share Posted April 3, 2008 But we don't get feedback do we? Surely not? So what is there to eliminate? Link to comment Share on other sites More sharing options...
mervaka Posted April 3, 2008 Share Posted April 3, 2008 stupid people who write glorifying articles on subjects they dont understand. EDIT: I should probably mention that my above statement is all in good humour :( feedback is an engineering problem, to which there is always an engineering solution! Link to comment Share on other sites More sharing options...
lightsource Posted April 4, 2008 Share Posted April 4, 2008 Aah, but the Guardian states... prevent feedback before it happens Most feedback destroyers eliminate feedback after it's occured, not before.... Still amusing though. :( Link to comment Share on other sites More sharing options...
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