Live Band Monitor levels for music festival

[Rocket_Dubs]

Hi

 

I'm currently doing a noise assessment for the surrounding area of a large rock concert (V Festival in Brisbane, Australia).

For the bands that are not using in ear monitoring systems we need to know roughly how loud the monitors will be in relation to the PA system. The PA will be approximately 105 dB at the mixing desk (40m away) and 137 dB at 1m distance from the PA.

 

So I need to know how loud in decibels the monitors could possibly be given how loud the PA is. Any help would be much appreciated.

 

Cheers,

 

Jack

[david.elsbury]

*sigh* This is an almost impossible question...

 

1) what wedges?

2) how many?

3) any sidefill?

4) what amps?

5) size of stage

6) what is on the rear of the stage (drapes, something absorbent? Something acoustically reflective?)

7) same as (6) but roof of the stage

 

A concurrent post has been automatically merged from this point on.

 

137 DB @ 1 m from the PA stacks? I'm not 100% sure, but isn't this approaching an unsafe level for anything over a few minutes of exposure?

[Rob_Beech]

I shall assume that the main PA is flown and as such nobody will be within 1m of it. Or hopefully not within 20m on axis to a box. I'm guessing that if this is a large system, there will be some trimming between sections of an array. The bottom boxes probably aren't going to be pushed like the top ones.

 

This is not TOO relevant but does play some part.

 

As for the monitors. Yes, it's nice to know more, but, in the meantime lets assume you've got industry standard wedges. 450's M4/2, LE2100's that sort of rubbish. All monitors capable of killing a horse at several feet.

 

The actual question you are asking needs context. Are you wanting to know how much the on stage noise is going to affect the noise out front and thus in turn affect your limits? Are you wanting to know what noise levels are to be expected on stage? Are you wanting to know what monitors you'd need given the levels you describe out front?

 

It's difficult to tell with all 3. But to work backwards. Outdoor festivals, it's rare that for most program material you'd expect anything less than a pair of monitors per mix, or per person. Though if you have say a brass section of 3 people you may have a pair between them. Program material is the key here. A metal band may want 4 a piece if they're stupid. A jazz trio might not want monitors at all.

The regular TFM450 LE2100 MAX or M2's etc are rider friendly boxes that do what they say on the tin.

 

Noise levels on stage at festivals are VERY VERY loud. I know, I've been both on the stage at many, and at the side of the stage contributing to it on many more. However that said. On anything but the smallest festivals the on stage sound (from monitors at least) shouldn't affect FOH too much.

 

So that leaves the middle answer. The people on the stage are close to the FOH PA but are off axis, they may find alot of LF material on the stage from the subs, but probably little MF and HF if the system is designed correctly. This works to their advantage.

 

We know that in order to hear something as a dominant source it has to be 6dB louder than everything else, at least. SO if on a stage with no noise source you get the FOH sound at 98dB say. Your monitors need to be 104dB at your ears for you to hear them as such. The same applies to everyone else. Of course, as you put in backline and drums and that annoying sod behind you blowing the trumpet right in your left earhole. the "unwanted" noise level increases further, so the monitors have to do this also.

 

Of course, this goes another stage further if you're not careful, your monitors will increase the stage noise again and another person will want their monitors louder, and the same applies until you have an astronomical volume level on stage.

 

From experience a musician can see levels of between 110 and 125dB depending on their program material. This is quite a range, but the louder bands really do suffer.

 

Remember. If a musician puts ear plugs in, don't automatically think, what a clown, why doesn't he just have his monitors quieter. He or she is simply reducing the OVERALL level. This includes the signal level (monitors) and the noise level (other monitors, deaf drummers drum fil, FOH PA, stupidly positioned front fills that are just bouncing all the HF off the crowd barrier and causing feedback you can't control from monitor world, backline, wind,). Their monitors still appear the necessary 6dB louder than the "noise" level. But the overall level is lower.

[nick7076]

add

 

where is the stage/monitor in relation to the pa?

 

Easy answer is that the stage monitor mix will be as loud as the performer requires it within the tolerance of feedback and maximum safe SPL

 

The above apeared while I was writing this!

[Rocket_Dubs]

*sigh* This is an almost impossible question...

 

1) what wedges?

We can't get that information, so we just want to know a worst case scenario

2) how many?

same answer as above (we will model it as

3) any sidefill?

same answer as above

4) what amps?

again, same answer as above

 

The next 3 questions aren't important, if we need to we model all these characteristics in our noise model (CadnaA) we will

 

5) size of stage

6) what is on the rear of the stage (drapes, something absorbent? Something acoustically reflective?)

7) same as (6) but roof of the stage

 

we just want to know what the maximum possible Sound Power Level (SWL) Scenario would be (for instance @ 1 m) . We will simplify any information we get for the purposes of the model.

 

A concurrent post has been automatically merged from this point on.

 

137 DB @ 1 m from the PA stacks? I'm not 100% sure, but isn't this approaching an unsafe level for anything over a few minutes of exposure?

 

Yes it is, but the client wants 100 to 105 dB at the mixing desk, so we initially model 105 dB. If you do the calculations that means approx. 137 dB @ 1 m.

 

Cheers for the response

[Rob_Beech]

At 1m from where?

 

The difference between out front and on stage is that on stage there are many sound sources. So you could stand in one place with nothing pointing at you and get a reading of 100dB. Then again, infront of a sextuplet of monitors for a deaf metal singer, you could get a potential theoretical maximum going on the boxes outputs of 150dB at 1m. Then again.. most people are over 1m tall. SO a 1m reference point is nice but it doesn't give any indication of exposure.

 

Also remember axis. Out front people are completely off axis to the monitors. So apart from right at the front you won't hear a deal on an outdoor festival stage.

[Charlie Jeal]

Rocket just talk to the system providers, at a guess up in Brisbane it's gonna be Norwest or Jands maybe Johnstones or one of the other large providers, and ask what they're bringing.It will probably be standard package for all the various legs of the fest so maybe L'acoustics gear if its Jands or EAW if its Norwest.

 

Charlie

[Rocket_Dubs]

SO do you mean that if you measure the sound power level on stage when just the PA is running, it is normal to just add about 6 dB to this? What I would actually probably want to know is the maximum amount they would add to this. At present we are just modeling it at 3 dB lower than the PA.

 

BTW, @ 1m is the standard amount of distance away from the sound source Sound Power Level (SWL) is measured at.

 

A concurrent post has been automatically merged from this point on.

 

Sorry about last reply, this may be a little clearer

 

 

"The actual question you are asking needs context. Are you wanting to know how much the on stage noise is going to affect the noise out front and thus in turn affect your limits? Are you wanting to know what noise levels are to be expected on stage? Are you wanting to know what monitors you'd need given the levels you describe out front?"

 

None of the above. We are modeling the noise levels at houses outside the perimeter of the festival

[Rob_Beech]

Ok.

 

Then David's Questions 5 6 and 7 DO come into play. Particularly 6 and 7.

 

If you are measuring on a perimeter all around then it is very important you know about the materials used, you need to know about the absorption of these materials. Remember the perimeter behind the stage is often quite close so monitors and side fills will play a key part in contributing towards teh noise level at THIS area of the site.

 

As for just adding 6dB. No, we can't do that unfortunately. As I mentioned, it can vary. On average it will be more than 6dB. You have to take into account the acoustic sound of drum kits, massive guitar amps, and other items. Then lots of monitors, sidefills etc. I'd expect the noise on stage to be anything between 12 and 18dB louder than the source without stage noise. Of course that is simply theoretical as one needs the input sources working to obtain the reference level out front. As previously mentioned, noise on stages can exceed 120dB, perhaps not continuously but who measures anything continuously nowadays.

 

With the greatest respect, it appears you are trying to obtain a single figure here without having to look into things too much. Houses outside the perimeter are not going to be suffering from levels proportional to those given at 1m whether it is a standard reference point or not. There is alot more to it than this. You have to look at array theory, and how arrays work, be it point source or line source. There is also the point of AXIS, whether a person is on or off axis to a number of boxes will determine the A and C weighted levels.

 

If we're looking at this from a noise pollution level then you may find that Low Frequency noise is the problem here. If so. There will only be minimal amounts from the stage. If however we're looking at a full range problem, then you'll find the stage contributes much more.

 

 

So, without giving us any information, if you want a maximum figure at the perimeter or at someone's property. then 112dB. We'll assume the rear perimeter is just behind the stage and there is a house just behind it. If the houses are much further away then it might be 60dB. I'm not sure how we are supposed to give a figure. As I mentioned previously the 1m reference point is NOT something you can use to calculate.

[Simon Lewis]

BTW, @ 1m is the standard amount of distance away from the sound source Sound Power Level (SWL) is measured at.

 

Why are you quoting SWL? I doubt if you have this data for the loudspeaker system! Usually, it will be sound pressure level that's quoted at 1m. Even this is likely to be an unrealistic figure. If you consider one element of a line array (say a JBL Vertec) its stated maximum peak output is between 138 and 146dB(SPL). It is unlikely that the box will reach those peak levels for any length of time, so the overall output is likely to be lower.

 

However, we may have a large number of devices in an array, with a varying degree of inter driver coupling - depending upon frequency and effectiveness of the waveguide. Therefore as a whole array, the total output may well be 10dB higher than your quoted figure (assuming 10 boxes coherently coupling).

 

By the time you take variation in programme material, loudspeaker power compression, atmospheric conditions and even crowd noise into account, trying to settle on a single figure for the noise sources is a rather difficult task.

 

The next issue is what level of directivity will you incorporate into your model? Although the stage system will have directional components, they face in many directions, and it may be easier to work with a nominal omnidirectional source, with the main speakers assigned with whatever reasonable level of directivity they may be expected to achieve. I'm guessing line arrays will be in use, so at least there should be good control in the mid to high frequencies. However, there may be a considerable difference in offsite noise impact depending whether normal sub stacks or cardioid sub arrays are in use.

 

For modelling purposes, you could simply put in the noise sources as you describe, but without some reasonably accurate data the model will not match the actual measurements taken at the event.

 

Simon

 

A concurrent post has been automatically merged from this point on.

 

As I mentioned previously the 1m reference point is NOT something you can use to calculate.

 

Strangely enough, that's exactly how it has been done. One of the first instances of noise modelling for a UK concert was in Birmingham - a University Ball event held outside among some of the University's buildings. The predicted noise levels at various noise sensitive properties were monitored by both the council and an external noise consultant (if I remember correctly).

 

The predicted noise levels were found to be considerably higher than actual levels because an omnidirectional source had been assumed and the effect of the large buildings adjacent to the stage had not been taken into account.

 

Noise models have been refined somewhat since then, but they are only as good as the input data.

 

Simon

[Rob_Beech]

I see, interesting.

 

Not the ideal way then clearly.

 

Simon puts my points better than I ever could, and adds alot of detail, and correction.

 

You are relying on a well designed array. If some clown has decided to put the top 10 boxes in a hang at 0degrees and 12degrees between the bottom 4 etc then I look forward to hearing Bobbsy's comments on the sound from his window. However, if it is well designed the noise level on the perimeter may be more controlled.

 

Predicting what someone may design is even more difficult and inaccurate than predicting the levels KNOWING the design.

[paulears]

Moderation: Please don't keep quoting entire chunks - I've just gone back and removed absolutely huge amounts of quotage of quotage, if you follow me. The posts are individually quite long, and adding in the previous 2 or 3 responses makes it really difficult to read - especially where quotes have got joined up or split by editing.

 

Quote specific bits, if you need to, but not then entire thing - please!

[Bobbsy]

I look forward to hearing Bobbsy's comments on the sound from his window. However, if it is well designed the noise level on the perimeter may be more controlled.

 

Well, I'm about 100km away from the venue but my patio does face directly towards them so I'll let you know.

 

More seriously, as far as I know last year's V Festival was at the same venue (Avica Resort on the Gold Coast). Aren't there actual measurements from a previous festival that could give a better idea than any speculative modelling? Or have there been substantial changes to the planned rig that make previous experience invalid?

 

Bob

[Simon Lewis]

More seriously, as far as I know last year's V Festival was at the same venue (Avica Resort on the Gold Coast). Aren't there actual measurements from a previous festival that could give a better idea than any speculative modelling? Or have there been substantial changes to the planned rig that make previous experience invalid?

 

Bob,

 

I'm sure that measurement data from the previous year will be used, but the environmental noise impact will depend upon the siting of the stage, the PA speaker type and deployment, and the nature / spectral distribution of the music*. That's where predictive modelling becomes very useful. Modelling is mentioned in this Australian environmental protection document, and there's an example of typical problem solving using modelling from MC2 here. Sometimes, knowing what the levels were simply isn't enough... we have to know why it was that level, and work out ways of maximising the concert experience without causing environmental problems.

 

The larger UK festivals will now have their noise strategy handled by such firms as Vanguardia, who will liaise with the local council and come up with some fairly accurate modelling and prediction to show that the concert impact is within the parameters the council will accept, and also provide expert off and onsite measurement during the event.

 

With regards to the OP, I'd like to know a little more background. It seems he's carrying out a modelling project as a maths student. This is a good project to work on, but there are quite a number of pretty refined environmental noise software packages already out there!

 

If anyone is interested (and I know that this is a pretty narrow field - even for this austere discussion group!) then the National Physical Laboratory give a good overview of the issues involved in this quite comprehensive guide.

 

Simon

 

 

*a quick example... some years back it was found that Madonna at the old Wembley Stadium triggered a handful of noise complaints but at another concert a few weeks later, U2 triggered dozens of complaints. The overall noise levels were (AFAIR) similar, but U2 employed a large number of Servodrive cabinets. Of course, measuring 1m from the facade of a noise sensitive property with a meter set to A weighting didn't help much ;-)

[Bobbsy]

Thanks Simon, that makes good sense.

 

I've just looked at the venue on Google Earth and it seems to be surrounded, with a housing development on one side and competing resorts in other directions. My wife (who has attended music events there, though not this festival) says that they tend to erect sound-reflective hoardings around most of the field where the event happens.

 

In any case, if this is to keep the "men in suits" happy (not to mention the people living near the site) it sounds like a specialist job, not something to be undertaken on the back of an envelope with a rudimentary knowledge of acoustics.

 

Bob