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gwilliamson
26-02-2007, 08:23 PM
Hi Chaps
Really need some help if possible. I have an installation of two 10 kw wall mounted Daikin Units in a classroom. In the book they are rated at 45Db High at 1 metre. The design consultant has just phoned me today and stated the maximum limit for any equipment in a classroom is NR30 or 39DB at 3 metres. I spoke to Daikin this afternoon to ask what the sound levels are likely to be at 3 metres and their advice was to use a sound meter after the install..Very helpful!!
Is there a definate way or calculation to work out the information i require?
Any help on this a big thankyou as have to phone the consultant tomorrow morning.
Thanks
Gareth.

Andy
26-02-2007, 11:37 PM
Hi Chaps
Really need some help if possible. I have an installation of two 10 kw wall mounted Daikin Units in a classroom. In the book they are rated at 45Db High at 1 metre. The design consultant has just phoned me today and stated the maximum limit for any equipment in a classroom is NR30 or 39DB at 3 metres. I spoke to Daikin this afternoon to ask what the sound levels are likely to be at 3 metres and their advice was to use a sound meter after the install..Very helpful!!
Is there a definate way or calculation to work out the information i require?
Any help on this a big thankyou as have to phone the consultant tomorrow morning.
Thanks
Gareth.

Hi Gareth:)

I have a spreadsheet that was given to me by a friend in another company. If I put in 45dba at 1m it gives me 35.5dba at 3m

http://www.engineeringtoolbox.com

will give you the formula if you need it and probably a program to work it out.

hope this helps.
Kind Regards Andy:)

momo
27-02-2007, 12:53 AM
Double distance: lose 6dB in open space therefore 39dB at 2m... however absorbtion and reflection in interiors must be taken into account:... at 3m I guess you should be ok for the required spec. A fan produces a whoosh similar to white noise, however motor noises are different and vibrations can resonate. Borrow a decent dB meter and check discreetly:D!

Jez
28-02-2007, 04:54 PM
Remember that there are two of the units, so you will need to add 3dB. The manufacturers data will be at anechoic conditions, so real sound will invariably be higher.

gwilliamson
28-02-2007, 08:26 PM
Many thanks Chaps for all your help.