Sound level cutoff meter

[KeepItSimpleStupid]

PS:
KISS works as opposed to the long name.

 

[stuee]

No problem KISS

 

[Reloadron]

You may want to look back at AudioGuru's post #19. Your concern I believe is the average sound level. Looking at the LM3915 data sheet on page 13 they give you a good example of an average detector, Figure 19. Precision Full-Wave Average Detector. Rather than screw around and worry about peak sounds triggering things and using multiple timers I would be thinking about using an average detector and getting the average sound level before running the signal into the LM3915. Get the audio conditioning out of the way. I would use the highest level output to drive a 555 one shot trigger circuit. When setting the 555 timing you can toss a pot in there so the timing interval is adjustable. I really don't see the time duration as critical as the interrupts will get your point across.

Ron

 

[stuee]

Yes ron, that does make sense having the average and not using 2 timers, how would i do this?
The interruption will be annoying but until this thing is in action i cant really work out a time to annoy people.

 

[audioguru]

ONE momentary "pop" sound that is too loud will trigger the first 555 and when it times out, the second 555 is triggered by it and cuts off the sound forever because the second 555 will never timeout with the first 555 holding its trigger pin low.
If the sound level is continuously too high so that the trigger pin of the first 555 is low when it tries to timeout then it will never timeout and the relays will do nothing.

The trigger pin voltage must be high (untriggered) when timeout occurs or a 555 will never time out. In your circuit if the sound is always too loud then the 555 timers will not work.
Here is a fix from the designer of the 555 IC:

 

[Reloadron]

Yes ron, that does make sense having the average and not using 2 timers, how would i do this?
The interruption will be annoying but until this thing is in action i cant really work out a time to annoy people.

I would do it as the data sheet shows in the link I provided. I would also use AudioGuru's suggestion for your 555 triggering.

Ron

 

[stuee]

So without being a complete noob (which i am) how woud i put all this together? i kinda understand it all but not sure how to get it all together correctly and would rather do right the first time than killing ic and parts

 

[Reloadron]

So without being a complete noob (which i am) how woud i put all this together? i kinda understand it all but not sure how to get it all together correctly and would rather do right the first time than killing ic and parts

Tomorrow, as time allows I will try and get what I see as a rough circuit as a starting point. My brain is sort of like oatmeal about now.

Ron

 

[stuee]

Hi Ron, did you have any luck with this as im putting it together now as i need it in place asap. Cheers

 

[Reloadron]

I did put something together but it didn't work well. Then I thought about just using a LM339 comparator circuit rather than the LM3914 or LM3915. Do you have any way to look at the audio levels on a scope? What I am curious about is the voltages.

Ron

 

[tomizett]

Whilst I'm all in favour of building stuff - and in case you're not allready aware - there are commercial products on the market which do exactly what you want. Many nightclubs and venues have them installed.

A few that came up on a quick UK google where:
https://www.noisemeters.co.uk/product/sentry/
https://formula-sound.co.uk/system-protection-noise-control/
https://noiselimiters.co.uk/

Of course, if this kind of device is out of your budget, there's nothing to stop you building one. My only word of caution is that, if lawyers get involved, you'll have more trouble proving the validity of the calibration of something you've designed yoursef than a commercial product.

As an aside, I'd prefer to have the limiter disconnect the speakers rather than cut off the power to the amplpifiers - this will lessen the chances of damage to your equipment.

 

[KeepItSimpleStupid]

Yea. disconnecting the speakers or an input, I think, would be the better choice.

Ron:
Typical is probably 1 V RMS. See https://en.wikipedia.org/wiki/Line_level for a discussion. Tape loops (remember them) are higher for some reason.

The real question is whether Balanced (XLR type) connections are being used?

 

[Reloadron]

Thanks KISS as I have no clue where he would get his signal pick off.

I also like tomizett's suggestion. For less than the circuit building savvy and not having the required parts a turn key solution is a good way to go.

Ron

 

[large_ghostman]

I can see some business problems with this. You got bad reviews for the system being too quiet. How are people going to respond to a system that keeps cutting out?
Also if it was me I would first of all have a member of MY staff there to monitor the venue, I dont like the idea of some drunk with a beer in his hand messing with me equipment! The other problem I can see is the person who moaned in the first place is still going to moan if the noise keeps oscillating, as in one min its loud then it goes quiet then it goes loud etc etc. From a business point of view why not have the suggested master switch in something like a key safe thats locked, meet your client on the day of the event explain the noise level issue (you should have done this before they book as well) and together set the master switch to an agreed level (as long as its within the law).
That way the customer cant moan the sound is too low and the neighbor cant moan if your within the limits. Putting something on that turns off the way you suggest is likely to get you worse reviews, most people at the function wont have a clue there is a noise limit system in place, they will assume the sound system is just broken and keeps dropping out. By all means build something but this to me is going to harm your business not help it, and I still dont get why you dont have staff there looking after your interest during an event.
Just my thinking thats all

 

[tomizett]

You could also install a limiter before your power amps to regulate the level they receive - then set the amp gains so that this is the correct maximum level in your room. It's simply a matter of physically ensuring that no public can get to the limiter or amps; put them in a locked cupboard or something.

 

[large_ghostman]

Lets face it we have all been there, you think you have a solution to a problem that requires something very smart. Then in the end you realize you could have saved money and done a better job without technology, the amount of over complicated not needed gizomo's I have built only to rip back out after a year or so and replace with a switch

 

[KeepItSimpleStupid]

The commercial methods aren't bad because everyone can see the levels especially the performers., so they KNOW when it will happen. The products seem to be a .uk thing and some of the ones I saw were not for 120 VAC mains. Who knows where the OP is.

So, the simple solution doesn't work. OK, you mess with this know, you don't perform here. That doesn't work because the Authority Having Jurisdiction said three strikes and your out.

In order to control, you have to measure.

 

[audioguru]

The products seem to be a .uk thing and some of the ones I saw were not for 120 VAC mains. Who knows where the OP is.

I think Stuee is in Down Under (Australia), MATE!

 

[Nigel Goodwin]

I think Stuee is in Down Under (Australia), MATE!

Which is why it's important to have your location filled in

 

[KeepItSimpleStupid]

So, the 220-240 ish commercial stuff from the uk could work.