How Loud is 95dB

[Tom]

(Disclaimer - I'm a Production Manager, not a Sound Technician - professional sound staff will be employed to rig and operate all equipment. No crew will be harmed in the making of this event)

 

We're organising a Gala Dinner, part of which will include an 8 piece band and a burlesque act.

 

The venue is a largish (15m x 42m), low ceilinged room and there will be 500 guests seated for dinner with a largish stage centred on one of the long sides of the room.

 

The venue have informed us that they have a 95dB sound limit - they have lots of problems with their neighbours and the roof is just a skin - think semi permanent tent. I've seen the dB charts (90dB equates to a heavy Truck / Loud shout while 100dB equates to a jet taking off or a train horn) but it's difficult to equate that to a band in a room situation. The venue is very nervous and think that even if the band playing acoustically it would go over their limit.

 

So... what am I likely to get away with and will it be any where near what I want to achieve?

 

The band line up is - 3 x Sax's, Trumpet, Trombone, Piano / keyboard, Bass, Small Drum kit and three vocalists.

We were planning to mic the vocalists, Bass and the keyboard and have a mic for the brass solos only. It's a much for balance as anything else. They need to have some impact (their an act, not just background music).

 

The burlesque act performs to a backing track only - no singing.

 

The plan is to have a good spread of speakers in the room to try and even things out. Does this help in terms of dB?

 

With a 95dB limit, will it be possible to amplify the band, or even for them to play acoustically (just micing the vocals).

 

Will the burlesque playback have enough impact to support the act.

 

Nothing needs to be overly loud - it'll me a mature, theatre going crowd.

What sound level would you expect to be getting on a gig like this?

Do I have a hope in hell?

 

Words of wisdom appreciated.

 

Tom

[dunk_1984]

95db where? You say you are restricted to 95db, but where is this measured from?

 

42m is a rather long room and 500 bodies absorb sound. It is un-realistic to expect to get even coverage without the use of re-enforcement, vocals, keys and bass certainly would need it, and I'd suggest everything be mic'd, how this is mixed is different to what is mic'd.

[ianl]

I think the important questions are : where does it need to be 95db? At what frequency? and is that average over time?

a room full of 500 people talking could get near that volume

if its 95db on the dance floor or just in front of stage or even on stage then you could have a problem. if it is at the perimiter of the venue then it could be ok

 

95db is probably the quietist you would want a gig , a drum kit can easily make over 100db without even turning a PA on

[Rob_Beech]

It all depends on the gig, and the people there. If it's a sit and listen audience then 95dB is more than enough. If its a lively audience then as Ian says, 95dB may be reached just with the audience.

 

As for where it's measured. Very true. If its 95dB at the back of the dance floor, maybe 7 or 8meters into the room. You are going to struggle to get the sound to the back at any useable volume (worse still if they're a lively bunch).

 

On the other side of things, if you aim for 95dB at the back of the room it is likely going to be extremely loud at the front. Speaker positioning can minimise this somewhat (if you have venue height available and the ability to point your speakers where you want them in both the horizontal and vertical planes. ) but it will still be somewhat louder.

 

With speakers just above head height, 95dB at 40metres will be about 107 (theoretically) at 10m. This is already extremely loud. The people on the dance floor are going to be subjected to volume at above safe levels.

 

A wireless Transmitter (IEM) and a pair of Wireless receivers and a pair of Powered speakers, and a delay unit may be an option here.

 

 

Rob

[Jivemaster]

95 is not loud in terms of band or acts. You can expect a bar full of talking people to be 85 - 90. Really everything depende on getting the guests quiet then 95 will just be enough for the acts. Keep the continuity announcer as low as possible so that people have to listen quietly. If tha announcements are done rock band style the guests will be that loud and you will not beat them!

[mervaka]

I've done acoustic acts at 85dB before, but it was a small room, and the audience were dead silent. was kinda creepy!

[Just Some Bloke]

According to the HSE,

The mean of published sound levels from rock concerts is [around] 100 dB.

 

They also say that 87dB is the

level of noise exposure which must not be exceeded

though this is averaged out over a working day/week.

 

Hope these figures help add to the ones you've already found!

[Joe]

All previous answers are far more helpful than mine, I simply include this as an example of what a PITA limiters can be.

 

I worked a venue recently with a limiter set "allegedly" at 95dB. This was a wedding reception, in a barn for 120 people. FIRST CHORD that the band struck up caused the limiter to trip turning off some room lights and (far more importantly) the chocolate fountains. I had put in place a work around to avoid the problems - just as well as without it the whole night would have been a shambles. I try and mix the band (regular clients doing functions etc) at 95-100dB at the desk, I have a meter for just such checks.

 

Some limiters are better than others in that they allow a decent time BEFORE cutting the power, this particular one was/is a nightmare, and makes the venue virtually unusable as the owners admitted that even audience applause has caused it to trip.

 

Find out where the measurement mic is located (how close to the band). Are the band going to be mixed from the floor or are they doing it themselves? If they have a sound guy, he can keep one eye on levels and hopefully minimise any issues. If the band are doing it themselves then someone is not going to be giving 100% to the performance as they will be watching the indicator lights :D

 

You do have a decent sized room and a good number of bodies in it - you may be fine - good luck

 

Joe

[Bobbsy]

Previous comments/questions about where in the room the measurement will be taken are entirely valid, but I think the OP's final few lines are very important...and being overlooked by some. As he says this is a "mature, theatre going crowd", I'd say that the audience's SPL expectations will be lower than some people are assuming. In a theatre situation (other than some rock musicals) 95db(SPL) at the audience is a loud patch in a fairly loud show.

 

As for a "theatre going" audience, it MAY be that they're used to watching shows quietly and will keep quite silent. On the other hand, being a dinner, they may wish to talk through the entertainment but (that being the case) they won't appreciate an attempt to drown out their discussions.

 

Frankly, subject to the question of where the measurement is taken, I'd say 95dB is quite adequate for the audience you describe and agree with Rob's advice about keeping speakers up high and possibly using delayed secondary speakers to keep levels even across the room rather than having hot spots at the front.

 

Bob

[Mr.Si]

I just want to be picky here.

 

I'll presume we're talking dB(A) (a broadband A-weighted figure) and in which case, there are some good comments above.

 

Going back to being picky, I wanted to further what ianl asked: "At what frequency". I say this because there's the "Equal loudness curves" issue with regard to the human ear's response to sound

between 1 kHz (1000Hz) and 3kHz (3000Hz) where approximately the human hearing is most sensitive, 95dB will be nasty. Those deafening High-mid screaming sort of sounds (think back to a moment in a bad nightclub on the dance floor, or lots and lots of girls screaming at a westlife gig - those sorts of frequencies.

 

However, 95dB at something like 100Hz or 250Hz are going to not nearly sound as loud. Indeed, in order for them to sound as loud as 95dB @ 1kHz, these lower frequencies would have to be cranked in their sound level to sound as loud. The same goes for higher frequencies, but not nearly as much.

 

Like Rob said, it also depends on the program material you intend to put through the speakers. As the balance of the frequencies in the mix will change a lot depending on what is played.

 

</ramble on>

[Tom]

Thank you all for your replies so far

 

Bobbsy, you've summed up the issues well and your words are reassuring.

 

I did ask where they were taking the measurement and they just said "in the room" - I don't really think the events manager knows much more about this than what she's been told. I'm taking the view (arbitrarily) that it's a level at the sound desk. But then it''ll only be about 12m from there to the front of the stage.

 

The venue doesn't actually have any measuring devise on site - we may take one in case we need to stand our ground but I really don't want it to get to that.

 

Any further thoughts appreciated.

 

T

[Rob_Beech]

95dB 12m away with a 40m room is going to make it rather quiet at the back. I'd reiterate my suggestion of a pair of delay boxes in this case.

 

That said, I'd be somewhat concerned with the level of Joe's mixing if he were to mix at 95-100dB at the desk if it were at the back of a 40m room. around 127dB at 1m (given the 3dB addition further back as you hear both sides of the system). All theoretical.

 

Boxes really high is the ideal way to combat this. Boxes on flying yokes is much much better still.

 

Rob

[Bobbsy]

I just want to be picky here.

 

I may regret this post because, at present my morning caffeine level is still too low...and I'm coming down with a cold too. I've had a bad run lately of mis-reading things until the caffeine is bubbling nicely, but anyway....

 

Mr. Si, don't your two items of being picky somewhat contradict each other?

 

Like you, I think it's most likely that any spec for maximum SPL is likely to refer to "A" weighting. This is the most common way...and makes sense.

 

However, if that's the case is it valid to ask "at what frequency" since "A" weighting specifies an average across the audible frequencies, in a curve weighted to roughly represent the Fletcher Munson curves for human hearing at the sort of levels we're talking about.

 

...so wouldn't you EITHER ask about/specify a broadband weighting curve OR ask what frequency, not both?

 

Or do I need to go and drink another cuppa before attempting to post?

 

Finally, just reiterate what Rob and I have said, 95dB(A) is likely entirely loud enough for your crowd IF it's even across the venue. However, with a typical "speakers on sticks" set up in the room you describe, to get 95dB at the back you'll be blasting the front...or if you stick to 95dB at the front, the back will be too quiet. Rob's suggestion of speakers up high, angled down is spot on, as is his mention of the possibility of delay speakers part way back.

 

Bob

[Shez]

The venue is a largish (15m x 42m), low ceilinged room and there will be 500 guests seated for dinner with a largish stage centred on one of the long sides of the room.

(My bold)

Presumably this means that the throw of the PA only needs to be up to 15m, not 40. It's a wide space though, which brings its own set of challenges...

[Rob_Beech]

Thanks for that Shez. I completely missed that. This does change things a fair bit. Completely infact.

 

It would answer a question I had but didn't ask "why is the desk so close?"

 

Well, to pretty much start again with the topic (I don't think I am the only one that missed that point) You wont get away with a pair of boxes. I would suggest a pair of boxes (still up fairly high, still pointing down) at the sides of the stage pointing in covering the middle 3rd of the room. And a second pair, possibly up a bit higher and pointing to each of the outer 3rds of the room.

 

95dB at the desk at 12m is fine if the speakers aren't straight infront the front rows and dancefloor.

 

Ideally you'd have the outer pair on a different send to the inner pair. Perhaps if your desk has matrix facilities you could use this.

The reason for this is that the sound of any backline on stage will be heard by the dancefloor and the other people in the middle, so it wont be required as much in the inner pair (particularly sticking to an SPL limit)

The outer pair however will lack backline if it is given the same mix. So 4 matrix sends here would be ideal. Alternatively you could use 1 for the inner pair (mono) 1 for the subs 1 for the left outer and 1 for the right outer. (if you have more than 4 matrix then you could make the inner pair and subs stereo too but I shouldn't think this will matter)