Noise Criterion 1 (NC1)

[RonHebbard]

Idle chit chat. Have any of you been involved with the construction of an NC1 rated performance space or had the experience of installing and optimizing systems in such a quiet space? In my case, I'm speaking of Toronto's Four Seasons Center, the home of the Canadian Opera and the National Ballet of Canada. Three basement levels below grade plus eleven levels above in the heart of downtown Toronto with subways, heavy trucks and sirens passing regularly yet unheard and unfelt. Every day I learned new tricks relating to things such as routing cables and fiber across isolation gaps in individually floated slabs. The company I was with, MacLean Media Systems, supplied, installed and optimized all aspects of the video, paging, intercom, monitoring, hearing impaired, effects, reinforcement and variable acoustics systems. Suffice it to say it was a great way to invest most of two years.
Go ahead, try telling me NC1 is unachievable.
Toodleoo!
Ron Hebbard.

 

[BillConnerFASTC]

I've never heard of NC 1. A recording studio is around NC 15 as I recall. Most high school spaces I work on are intended to be around NC 25. I was in a NC 18 or 19 auditorium, and the silence was deafening.

 

[RonHebbard]

I've never heard of NC 1. A recording studio is around NC 15 as I recall. Most high school spaces I work on are intended to be around NC 25. I was in a NC 18 or 19 auditorium, and the silence was deafening.

Meyer has a bit about it on their website:
http://www.meyersound.com/news/2007/four_seasons_toronto/?type=25
The following is quoted from the Meyer link above:
"One thing that speaks well for Meyer Sound is that, when everything is on, this room still retains its N1 noise rating: dead quiet. You don't hear anything. We have to satisfy the ears of people who listen to opera unamplified. They can pick a hiss out of nowhere, and just become incensed by it."
I've never been one for saving programs and credits but working on that space is one of two credits I'm proud of.
As you mentioned, working in there by yourself when everyone else had left for the day was extremely eerie.
There are construction and installation techniques in that space that aren't taught in school.
I always giggle when someone claims BSS or QSC are too noisy with too much residual hiss or hum. We installed a ton of both in there and you can't hear them either.
Edited to add quote from the Meyer article.
Toodleoo!
Ron Hebbard

 

[FMEng]

If it was NC1, it seems like someone grossly over specified it, and they may have unknowingly multiplied the construction costs by many times. Was there a benefactor with unlimited funds dictating the results?

The expense and difficulty go up exponentially as the noise level drops. There is also a point at which there is no benefit to lowering the NC level for the intended use. Just the existence of an audience in a hall raises the noise level even if they are in rapt attention, so there is no point in trying to get the structure and mechanical systems below a certain point.

Our radio studios are around NC15, and the weakest point is the seal on the acoustic door.

 

[RonHebbard]

If it was NC1, it seems like someone grossly over specified it, and they may have unknowingly multiplied the construction costs by many times. Was there a benefactor with unlimited funds dictating the results?

The expense and difficulty go up exponentially as the noise level drops. There is also a point at which there is no benefit to lowering the NC level for the intended use. Just the existence of an audience in a hall raises the noise level even if they are in rapt attention, so there is no point in trying to get the structure and mechanical systems below a certain point.

Our radio studios are around NC15, and the weakest point is the seal on the acoustic door.

I had nothing to do with the specs, or the budget. After all the trades and sub-trades were hired, about forty of us were summoned to a meeting where the general contractor, PCL, told us we were to aim for NC0, which is theoretical, and they'd "settle" for NC1. As I've already stated, it was quite the experience. The referenced Meyer article answers many questions and credits many companies and individuals. After this project Meyer engineered a few more features to make their powered speakers even quieter when idling. (If you drive the speakers hard enough for their fans to run at high speed, the instant you mute the system, the fans quit and are silent before the reverberation has decayed.) You're definitely correct about audiences, they make appreciable noise just breathing.
No, I don't work for Meyer. (or BSS or QSC either.)

FME; Your mention of door seals reminds me how impressed I was with the door seals on the sound locks of New York's Lincoln Centre's Avery Fisher Hall. Those doors, and their seals, were VERY impressive.
Toodleoo!
Ron Hebbard.

 

[BillConnerFASTC]

Google noise rating and noise criterion - they're different. I commented on NC.

 

[RonHebbard]

Google noise rating and noise criterion - they're different. I commented on NC.

And your point? My point was to spark conversation and I seem to have succeeded. I learned a lot of new, to me at least, construction and installation techniques on that project. Unlike yourself, there may be others here to whom everything isn't old hat / boring and beneath their dignity who could benefit from some of the techniques I was exposed to and was willing to share.
Toodleoo!
Ron Hebbard.

 

[BillConnerFASTC]

My point is simply there are no NC1 rooms, there may be NR1 rooms. A quick glance suggests NC15 is close to NR1. I suppose it only the difference of saying 0 degrees C or 0 degrees K, but we're I standing there, its a big difference.

Yes, it's pretty amazing the lengths you have to go to have a really quiet room in a very noisy environment. As I recall the Four Seasons Center is a concrete box "floating" inside a concrete box. The inner box is floating or sitting on some sort resilent pads. Any connections - pipe and wire, lateral bracing, ducts, plumbing, etc. - would all incorporate some sort of resilency. Ducts would have mufflers. Doors would seal well. Smoke vents on stage are toughest unless money is no object what so ever.

 

[AlexDonkle]

My point is simply there are no NC1 rooms, there may be NR1 rooms. A quick glance suggests NC15 is close to NR1. I suppose it only the difference of saying 0 degrees C or 0 degrees K, but we're I standing there, its a big difference.

That's essentially correct. NR0 and NR1 both actual ratings mostly because NR "Noise Reduction" is officially defined by a BS formula so you can create any rating you want. NC "Noise Criteria" is a fixed set of curves defined by ASHRAE as far as I know so officially there's no rating below NC 15. NR is standard for Europe, while NC is more common in the US (although some concert halls use the more recent RC "Room Criteria" on more recent projects). Also, technically to achieve NR1 requires a negative noise level at the upper frequencies, so unless you've created an acoustic black hole... Haha.

Concert hall sound and MEP noise isolation can be very impressive though. Box within a box really requires a good structural engineer to work with, and a lot of checks during CA since it's not a normal construction method. My personal favorite recommendation though is a consultant who insisted on vibration isolation of all the electrical conduit because of hum concerns in the copper conductors...

Bill, do consultants on your jobs spec the STC rated smoke vents on most projects? (I've never heard of an issue with those, or are they just much more expensive)

 

[BillConnerFASTC]

Bill, do consultants on your jobs spec the STC rated smoke vents on most projects? (I've never heard of an issue with those, or are they just much more expensive)

Yes, most often. Very quiet areas and very low budget, maybe not. Probably near double the cost (though just the vent, not install ). Heavy roof construction is generally the bigger issue.