Jump to content

Sound Containment


JakeCTG

Recommended Posts

Hi

 

I have a gig comeing up in a marquee and need some advice on sound containment.

 

There are neighbours relitively close and when there has been wedding receptions in the marquee, the neighbours have complained with just the level of a bass amp and we are putting a full concert PA rig in there.

 

I was told by the local council that I needed to keep the level at the closest house at 40db which is about 300 meters away. What can I do to try and keep in this limit?

 

Any help would be much appreciated.

 

Thanks

 

Jake

Link to comment
Share on other sites

If the council say 40dB then you have real problems.

 

I've copied a few examples for you - for convenience fromhere.

 

Source Power		 (watts/m2)	  dB SPL
Threshold of pain		  10		   130
Jet takeoff from 500 ft.	1		   120
Medium-loud rock concert	0.1		 110
Vacuum cleaner from 10 ft.  0.00001	  70
Normal conversation		 0.000001	 60
Light traffic from 100 ft.  0.0000001	50
Soft conversation		   0.00000001   40
Whisper from 5 ft.		  0.000000001  30

 

At 300m mtrs, you have to reduce concert level down to soft conversation level? I suspect they know you can't meet this requirement so the event won't happen.

 

 

edit - all my careful column alignment has had no effect at all - sorry

Moderation: Fixed!

Link to comment
Share on other sites

So, quick BoFP (Back of Fag Packet) time...

 

300m from a point source, loss is 30dB

Absorption over 300m of grass, about 4dB

 

giving you a max SPL at the PA of 40+30+4=74dB before you account for any loss in the tent walls which, to be honest, at the important LF end is zero. <---very BoFP

 

40dB is a very low figure, it sounds as though there have been major problems in the past and you're being 'punished' for them. How big is your budget? You might need to get an expert on your team to negotiate.

Link to comment
Share on other sites

I was told by the local council that I needed to keep the level at the closest house at 40db which is about 300 meters away.

 

Presumably that is the noise of the entire event including the audience singing, shouting etc.

Link to comment
Share on other sites

dB Leq is an equivalent level which is the steady sound level that, over a specified period of time, would produce the same energy equivalence as the fluctuating sound level actually occurring.

 

In principle there is no upper limit as long as the duration is short enough so that the average is less than the 40dB specified.

 

Most instances I have come across have usually been an 8 hour duration (considered the normal working day). Any time duration can be used though, or it could be the continuous noise level during any one hour period over the 8 hours, so you would need to find this out.

 

If the 40dB Leq was for a full 8 hour period you can up the level by 3dB for every halving of the duration. If you are performing for 2 hours the average level could be 46dB. Again remember this is an average measurement so with a typical live band where the peak to average level is about 14dB (highly dependent on music type) the peak level could be up to 60dB. If you mess around between numbers this will bring the average down too.

 

If you then work backwards based on the 6dB loss for each doubling of distance you would be up to a peak level of about 100dB in the marquee. If there are obstructions between “you and them” this might give additional attenuation. So if you don’t play bass heavy material, point the speakers away from the neighbours it might be doable if not loud.

 

However, even if you think you have sorted everything out you need to take the weather into consideration. I live about half a mile from the M6. Depending on the weather it varies from being able to hear the traffic clearly to not knowing it was there.

 

I’m actually surprised that the council gave you a figure. In most of the instances I have been involved with the bottom line has been that if there are complaints it is too loud whatever the meters say.

 

The best advice I can give is to maintain a good dialogue with the council and if possible the neighbours who are likely to complain. Find out exactly what their 40dB Leq means. If they see you are taking the problem seriously and trying to comply you are less likely to have problems if you stray over the limit by a small amount. If you go down the rock ‘n roll confrontational route you will lose.

Link to comment
Share on other sites

If the aim of the council is to prevent entertainment at the venue, why didn’t they just refuse an entertainment licence, or revoke it if one already existed?

 

You really need to talk to people. Who on the council specified the 40dB Leq and why did they choose that figure. Was it someone on a parish council who plucked the figure out of the air, or an experienced environmental health officer? In some instances the authorities think that the complainant is a pain but are obliged to act anyway.

 

If it is a one off gig it might not be worth it for you to put in much effort chasing the answers to all these questions. Have the council enforced the limit on the venue/promoters? I’m curious why if this is a small one off gig where you are providing sound, or performing, the council have contacted you?

 

Good luck.

Link to comment
Share on other sites

The council should state whether their limit is A weighted (it usually is) and the duration of the Leq reading (to avoid long integration times as discussed above). Typically, it's 2 or 5 minutes. The 40dB figure is probably trying to ensure that the WHO organisation's suggested nighttime bedroom noise level of 35dB(A) isn't exceeded.

 

In the evening - with a moderately busy road nearby, it can be hard to get the SLM to read below 45 - 50 dB(A) simply due to background noise. The suburban locations I used to check didn't get quiet enough until around 11.

 

The next issue is whether the event is actually measurable as a distinct sound source. However, this doesn't have to be a barrier to enforcing a noise prohibition notice, as the EHO can state that he considers in his judgement it to be a noise nuisance, not that he has measured it as such. In fact, in stating a figure they have made a rod for their own back as they will have to go out and measure it! Of course, any reading you take will not be considered valid (even if you turn up with a class 1 B&K).

 

In terms of getting the noise down, can you work on getting the speakers close to the audience, baffling the loud instruments / back of stage with large sheets of ply, pointing the whole band/PA away from the dwellings etc. Some large events have used Eve Trackway behind the stage to reduce the rear radiated energy. I'm not suggesting you try this, but if (for example) you have a large truck handy, can this be parked strategically?

 

Lastly, is this a permanent venue? Councils aren't usually too over the top for reasonable one off celebrations. If it's a pub / hotel with half of Live Aid being brought in every Saturday night, the noise limit might be understandable ;-)

 

Simon

Link to comment
Share on other sites

Hi

 

 

This is a perminentle set up marquee that has some wedding receptions at there has been some concerts there before and the council has had complaints. When they have had complaints it was outdoors with the stage facing the houses, We are having it in the marquee and the marquee will be faceing side on to the house so this will hopefuly eliminate some noise.

 

We are bringing in a full FOH pa roughly 4K and useing about 10K of lights so it isn't going to be small and we are hoping to do one again next year.

Link to comment
Share on other sites

Without carefull liason with the venue licence holder and the council's Environmental Health people you will get tapped on the shoulder and told to stop!

 

GET HELP NOW! or your gig and reputation, and the venue's licence are at risk.

Link to comment
Share on other sites

Hi Brian

 

Your level drop over distance calcs need a better fag packet!

 

30M is 30dB

300M is 50dB

 

You are 20dB out. Obviously this is very significant in this case.

Not wanting to just be picky........

 

Ok here we go....

All measures here are ENL (event noise limit) and are based on Leq with time averaging over the whole event.

Whole event means from first act to last act.

 

For temporary venues with 1 event per year (I guess this is not you):

09:00 to 23:00 allows +25dBA increase in background level at facade of noise sensitive location

09:00 to 23:00 allows a maximum of 75dBA at the facade

After 23:00 No increase in background allowed. This means your event noise needs to be effectively 10dB below background.

 

For temporary venues with no more than 12 events per year (may be you):

09:00 to 23:00 allows +15dBA increase in background level at facade of noise sensitive location

09:00 to 23:00 allows a maximum of 75dBA at the facade

After 23:00 No increase in background allowed. This means your noise needs to be effectively 10dB below background.

 

For venues with more than 12 events per year:

09:00 to 23:00 .. maximum of +5dBA allowed over the LA90 background level. LA90 is the Aweighted level that the background exceeds 90% of the time.

After 23:00 you must be inaudible at the facade... inaudible means what it says.

 

--------------

The statutory instruments the council will use are:

 

The Control of Polution Act 1994 (COPA)

and

The Environmental Protection Act 1990

 

Section 57 says

".... where the Authority is satisfied that a noise nuisance exists, or is likely to occur or recur then it shall serve a Notice requiring the abatement of the nuisance or prohibiting its occurence or reoccurrence."

 

The problem you have is that there is no level that we can talk about where nuisance can be said to exist or not exist. This is down to the punter at his house and the man from the EHO. What will help you is if you know your acoustics then you can ask better questions of yourself and those around you (including the EHO man).

 

Bottom line. If some crazy pub landlord has decided he can make a few quid sticking a marquee in his beer garden and event noise is pissing off the locals then I would complain also!

 

Simon has some good stuff above. Barrier attenuation can offer you up to 10dB of extra help.

Watch out for temperature inversion after a hot summers day. The evening cool down can/will diffract radiated sound energy that was going into the sky and bang it down on the head of Mr Angry.

 

..... BTW Simon's WHO NR 35dB bedroom spec (indoor) and my 75dB(A) at the building facade (outdoor) limits is in keeping when you consider that a double cavity brick wall is good for DnTw of 40dB (minimum).

 

Cheers

 

Mark

 

 

 

So, quick BoFP (Back of Fag Packet) time...

 

300m from a point source, loss is 30dB

Absorption over 300m of grass, about 4dB

 

giving you a max SPL at the PA of 40+30+4=74dB before you account for any loss in the tent walls which, to be honest, at the important LF end is zero. <---very BoFP

 

40dB is a very low figure, it sounds as though there have been major problems in the past and you're being 'punished' for them. How big is your budget? You might need to get an expert on your team to negotiate.

Link to comment
Share on other sites

Here's a bit of a whacky idea regarding sub bass:

 

If you want to minimise the amount of bass that gets radiated off to the side of the stage - how about placing one bass bin behind another from the point of view of the audience. Pick a frequency you most want to eliminate from the point of view of the houses over to the side (prolly the middle of the subs' range) - space the subs 1/2 a wavelength apart and invert the polarity of the back one.

 

From the *side* of the stage the subs are out of phase, and you should get some phase cancellation - but if they're spaced 1/2 a wavelength apart they're in phase(ish) from the pov of the audience. You might get some weird effects in the room, and I don't suppose it'd drop the spl over at the houses by more than a few dB, but if a) isn't too severe and b) is useful, it could be worth a punt.

 

Eg:

Another BoFP calculation:

Subs do most of their business around 100Hz, speed of sound about 340m/s so wavelength = 3.4m -> one sub 1.7m behind the other.

Aiming for 80Hz, speed of sound 335m/s (cold night) -> wavelength = 4.2m -> one sub 2.1m behind the other.

 

I have no idea if this would actually work, but I'd be very interested to find out one way or the other if you're daft enough to try it.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.