Average ambient noise levels

[Stuart91]

I've got an interesting situation brewing for a festival I'm covering later in the summer. It takes place on a pedestrianised shopping street. There have been noise complaints in previous years (mainly one vocal person who is implacably opposed to the festival). As a result, the local council have imposed some noise restrictions.

 

The limit I have been given is 65dB (no weighting stated). This figure has apparently been arrived at by assuming that the ambient noise will be around 50dB, and allowing me 15dB of "headroom" above that. This seems like a ludicrously low figure - we might almost be as well not bringing any PA at all! I am pretty sure that the ambient noise will be well over 65dB but have no easy way of proving it. Festival management were hoping to get an acoustic consultant to take some measurements but it doesn't look like that will be possible to schedule ahead of the event.

 

Is there any even vaguely authoritative source that I could cite, with typical figures for this kind of thing? It's a busy shopping street, with market stalls and open air eateries. There is a quite heavily trafficked road about 40m away from one of the measuring points. I'd like to be able to at least have a coherent argument for a more sensible limit.

[Simon Lewis]

Has the council quoted this figure directly to you, or has it come via the festival organiser?

I would want to know at what point noise would be measured, the weighting and time period for Leq (which they must surely be using!).

 

If the council is not well versed in this, it's conceivable that they are (badly) quoting from the now defunct Noise Council's guidelines for music from open air events in urban areas.

Here's the document

 

If they really do not know what they are doing, then one of the acoustic consultancies specialising in batting for festivals may be worth contacting (Vanguardia is probably the best known).

Edited June 25, 2017 by Simon Lewis

[Stuart91]

Simon, you've hit the nail right on the head. That's the exact document that I've been given.

 

The email that I've seen from the council to the organisers didn't mention any weighting etc., just the measurement positions.

 

Reading between the lines, I get the impression that the council folks don't have much experience of this kind of thing.

 

BTW "Noise Council Working Party" would be an excellent name for a band...

[pete10uk]

That figure is way too low for anything useful.

 

I've just done an install in France and the venue has had council fitted limiters installed, while I'm not an expert in venue limiters or correct acoustic measurements, I can tell you when it hit 82db the system shut down dead, that was 82db on the limiters screen and my iPhone spl app. It was hardly loud enough for a cough at 2m. The annoying thing was the bar 4 doors down was kicking out 84db from the other side of the street.

[Stuart91]

It was hardly loud enough for a cough at 2m.

 

There's a venue like that near me. If the crowd cheer too loudly the power cuts off. Which is fantastic during the first dance at a wedding.

 

 

That figure is way too low for anything useful.

 

That's what I reckon. The real problem is that the event licence depends on us at least appearing to keep within these levels. Unless the council can be persuaded to take a more enlightened approach to the situation.

[Simon Lewis]

The real problem is that the event licence depends on us at least appearing to keep within these levels. Unless the council can be persuaded to take a more enlightened approach to the situation.

 

The guidance is from 1995 but is still used because not so much has really taken its place. However, it's designed to help control noise from concerts held in stadiums or football grounds, and arose after their popularity spread in the 1980s.

 

The idea is a good and simple one - the noise level at (2m from the facade of) the nearest noise sensitive dwelling from the stadium should not exceed the stated value. The level is lower if the numerical frequency of such concerts is higher or if the venue is sited in a more urban location. It was designed to let major gigs take place at such venues without them being completely overpowering and giving rise to multiple complaints.

 

In this case, it seems as if the code may be being applied somewhat incorrectly. It's also worth noting that " First published in 1995, the code does not take account of the Licensing Act 2003 and, until it is possible to up-date it, it should only be used with caution. ".

Have a look at the guidance that the Local Authorities Coordinators of Regulatory Services produce. Work out what the likely attenuation will be from your stage to the measurement points. Consider what mitigation can be achieved in terms of reducing stage level and bleed from PA (directivity of main PA and subs etc.)

 

Noise control is a fact of life, but I suspect that if the levels for this event have not been set sensibly, you will need some outside help to negotiate. Do bear in mind though, the original guidance is not discussing 65dB LEq at mix position.

 

 

 

 

[ghance]

Morning Stuart

 

Simon is spot on with his advice, but I'd like to add a few observations.

 

The Noise Council Code of Practice has indeed been criticised, but there is no commonly adopted alternative. In practice arguing for different noise criteria will be difficult unless you have some unique circumstance in mitigation. Would you want to be the Environmental Health or Licensing person who opens themselves to criticism from bosses or the general public for not enforcing the defacto standard? One of their objectives is to uphold the expected standards for protecting the public. In my experience the best approach it to proactively work with the responsible authorities, event organisers & residents to minimise the likelihood of complaint & therefore upholding the licensing objectives to prevent public nuisance.

 

It is true that some local authorities have more experience than others with live music events, but assumptions are best avoided. These people will have often worked at a few different authorities & some will have diploma in acoustics. Sharing skills & expertise is a positive way forward. For example, you as a sound engineer will understand what PA configurations will help contain the sound where you want it as much as practicable, and how to mix a band that sounds full without necessarily operating at high volumes for long periods.

 

In my experience avoiding complaint is the most powerful argument for what is a workable level that does not disturb residents. In practice, complaints do not always correlate to the perceived or measured levels. The general level of disruption overall, sensitivity to noise, what disturbance occurred in the preceding weeks (such as roadworks), fear of a repeat of a previous noisy event, the type of music and so on.. i.e. the music noise level is only one factor to the complaint.

 

The criteria of a Music Noise Level of 65dB LAeq 15' at 1m from the facade of any noise sensitive premises is a default setting for 80% of events. The Music Noise Level is just the noise of the music & not the sound of everything else with the PA off (aka residual level). Achieving compliance depends on the activity & location. A rough calc will give you an idea of the kind of level you can expect in the audience.

 

For example, let's assume:

 

The event is on hard ground

The site is relatively open & not excessively reverberant

The nearest noise sensitive receptor is 40m off-axis from a point source loudspeaker

You wish to achieve an average level of 88dBA for the audience 10m from stage over a 15 minute period

 

If you calculate the sound power at the source, deduct attenuation for noise propagation over hard ground and apply corrections for off-axis response and facade measurements, a Music Noise Level of 65dB LAeq 15' could be potentially achievable.

 

I have a bit of experience in the area, please PM if you would like to continue the conversation.

 

All the best

 

Gareth

Edited June 26, 2017 by ghance

[kerry davies]

There is nothing technical you can do about complaints from someone implacably opposed to the event. I suspect that, like I have in the past, you will get complaints when the PA is still on the van, the generators are off and the band still in bed. It is a question of working with your EHO to do your best and allowing the EHO to do their job and deal with the complainant.

 

Danny Dsharp is the man for this. He has spent thousands on trying to satisfy a couple of residents who actually do complain when the PA is off and you can't measure anything because they are the other side of a railway embankment from the site. They still moan incessantly. My solution suggestion was to send them on a Spa weekend but they didn't want an expenses paid holiday, they wanted to stay to complain.

[MarkBarl]

That sounds like an unworkable figure. I regularly see 70dBA + at indoor gigs just in the interval with the audience talking. A passing car at 7.5m is listed as 75dBA.

[Simon Lewis]

That sounds like an unworkable figure. I regularly see 70dBA + at indoor gigs just in the interval with the audience talking. A passing car at 7.5m is listed as 75dBA.

 

The Music Noise Level at the nearest noise sensitive dwelling is 65dB LAeq(15min). As the 1995 guidance suggests, it's meant to be measured in the relative absence of background noise, or at least a correction made for it.

 

....It is true that some local authorities have more experience than others with live music events, but assumptions are best avoided. These people will have often worked at a few different authorities & some will have diploma in acoustics.

 

Gareth - thanks for your wise comments. I'm not advocating calling out the "less experienced" EHOs, but just being aware that some may default to more predictable positions ;-)

I do sometimes wish that slightly more emphasis was placed on electroacoustics in the IoA diploma. There used to be a "sound systems" module many years back, but sadly it was dropped.

We discussed noise control at some length at the Reproduced Sound conference in 2015, and a telling fact from one of the SSE guys was that 90% of the effort they spend in planning for festivals is the noise control aspect.

 

 

 

[Shez]

Last time I did noise monitoring for a festival, we were given that same 65dB figure with a 5 minute LAeq along with the addresses of various properties containing known complainers. All of which had a main road right in front of them. Recording baseline figures without PA did of course register above 65 and whilst PA was audible during the event itself, it didn't show up on the meter readings. There's a human element here too - your ears will tell you whether the noise is potentially objectionable even if the meter says it's OK. We had to pull the headliners early as they were known for being very subby (and their engineer wouldn't budge on that) and that low end was travelling rather too well. Borderline on the meter but it was the kind of frequencies that make windows rattle and that really wasn't on.

 

We tried the offer of free holidays too - no go - some people just like to complain.

 

Stuart - can't you take a meter to the location in question to get some numbers for the ambient levels? I suspect many folks don't have much concept of what 65dBA sounds like; depending on which table you believe, it's somewhere between conversational speech and a dishwasher...

[Stuart91]

Thanks for all the contributions this morning.

 

Alas the festival site is 6+hrs away from me, so I don't have the option of doing anything in advance of actually arriving there. I am scheduled to be in the vicinity for a couple of days running in, so I could try and take some measurements then.

 

 

The event is on hard ground

The site is relatively open & not excessively reverberant

The nearest noise sensitive receptor is 40m off-axis from a point source loudspeaker

You wish to achieve an average level of 88dBA for the audience 10m from stage over a 15 minute period

 

That's pretty accurate. It's a hard-paved pedestrianised street. The way it's laid out we have buildings down both sides, maybe 10m either side of the stage, and another ~30m in front. I've been there once before and it didn't feel too reverberant - there wasn't any noticeable slapback on stage, for instance.

 

The organisers have been quite careful with their choice of acts. The most worrying band has a lot of brass in their line-up. I figure 88dBA in the audience wouldn't be unrealistic.

 

I'm a bit limited in terms of truck space, but I'm planning on using some cardioid subs, and small format line array cabinets. We've done some plots on the subs that indicate ~30dB reduction in level behind the stage. I figure the main arrays will just need to be aimed quite sharply down. Hopefully there will be enough audience in front of the stage to minimise bounce off the ground.

[pete10uk]

As I said in my earlier post, I'm not an expert in acoustic measurement or interpretation. Is there any not too heavy source of information to have a read up on?

 

I have a feeling that this is going to be come more of an issue going forward, and it is always nice to be able to get into constructive conversation instead of sticking my heading a bucket of sand.

[Simon Lewis]

Pete,

 

Lots of stuff online - look for Control of Noise from Licenced Premises / Pubs and Clubs / Control of Entertainment Noise / Control of Noise from Outdoor Events etc.

Most councils have a guidance page.

 

Environmental Noise is covered by a number of regulations, there's a list here. A lot still hinges on EPA1990.

 

With the licencing procedures now in place, these can actually work in your favour. If a time and event LEq limit is agreed, set and adhered to, then the council may be "less sensitive" to noise nuisance complaints as they have allowed you to run at that level. Exceed it, and you will be asked to turn down or stop, and possibly jeopardise future events...

 

Simon

 

... I'm planning on using some cardioid subs, and small format line array cabinets. We've done some plots on the subs that indicate ~30dB reduction in level behind the stage. I figure the main arrays will just need to be aimed quite sharply down. Hopefully there will be enough audience in front of the stage to minimise bounce off the ground.

 

These are the words that they will want to see.... planned mitigation, with prediction and monitoring...

Hopefully you have an SLM that will measure L(A)eq? If not, look for a suitable integrating meter (I like the NTI XL2) or if you have an iDevice, consider the Studio Six Digital software, preferably with a proper mic / preamp. Failing that, Smaart with an external mic and a calibrator is good...

 

 

 

[Stuart91]

One of our guys bought a posh meter a few years back. I can't remember the exact spec but I'll get him to dig it out. It might be worth getting it calibrated beforehand.

 

I've got Smaart, and some calibrated mics, but I'm not sure I'll have the chance to set it up properly - timings are tight and the mix position is sidestage so a handheld solution may be simplest.