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Acceptable DBa levels

Acceptable DBa levels

Acceptable DBa levels

I'm trying to find some literature somewhere where I can find acceptable or recommended DBa levels for varous building types so that I have a basis for sizing Sound attenuators.  I couldn't seem to find anything in ASHRAE and local codes do mention anything with respect to that.
Anybody have any input on that ?


RE: Acceptable DBa levels


RE: Acceptable DBa levels

OSHA is more for maximum sound levels for working enviroments. For 'comfort' sound levels ASHRAE Fundamentals Handbook lists various sound levels for different enviroments.

Depending on the application NC levels are a more common method of specifying sound levels in a building (dBa is used for outdoor applications). Typical NC values range from 20 in a theatre, 30 in a classroom, 35 in an office and 40 in a corridor.

Some of the silencer manufacturer's have good info on sound:



As I reach the end of this post I now question.. what kind of sound application are we talking about?

RE: Acceptable DBa levels

I recently observed the same thing.  A client specification referenced ASHRAE requirements.  I found no requirements in the ASHRAE specifications that I found.

IMHO, the HVAC noise level should be well below 70 dB in any occupied building.  I am specifying the HVAC for a non occupied analyzer shelter to be below 72 dB EXCLUDING the auxiliary ventilation fan that is activated upon detection of any hazardous or toxic gas.  A reply from a package HVAC supplier to my inquiry was that sound attenuation can reduce the noise leve around 10 db, into the high 60's or low 70's.  These buildings can be very small with a very live acoustic interior.

RE: Acceptable DBa levels

Thank you for your responses. The application I am specifying for is an office building.  The Sound Attenuator Rep who was helping me with the selection asked me what kind of DB levels I'm trying to achieve.  And that's when I started to research this.  I agree about the NC levels.  When I size diffusers and such I try to stay less than an NC of 35 for "typical" office environment.

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