I have researched authoritative sources of information on noise level guidelines for office environments, and have listed 3 sources below. None of them are above 50dB(A).
1) BS8233:1999 –“Code of practice for sound insulation and noise reduction for buildings” recommends 40-45dB LAeq for private offices and small conference rooms, and 45-50dB LAeq for open-plan offices.
2) “Level of noise data”: Extract from 1995 American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Handbook, HVAC Applications, Chapter 43, Table 2.Admissible Maximum Levels of Noise:-
Office Buildings
25-35 Executive and private offices
25-35 Conference rooms
25 (max) Teleconference rooms
30-40 Open plan offices
40-45 Circulation and public lobbies
40-50 Research, extensive telephone use, speech communication
35-45 Group teaching
25-35 Churches, mosques, synagogues
Laboratories (with fume hoods)
45-55 Testing/research, minimal speech communication
The values and ranges are based on judgement and experience, not on quantitative evaluations of human reactions. They represent general limits of acceptability for typical building occupancies. Higher or lower values may be appropriate and should be based on a careful analysis of economics, space usage, and user needs. They are not intended to serve by themselves as a basis for a contractual requirement
3) Australian Standard, AS 2107: Acoustics – Recommended Design Sound Levels and Reverberation Times for Building Interiors.
For open plan offices the recommended levels are 40-45dB(A)
There is interesting information from HP, in the form of “HP PCs and Acoustic Noise- Background information on PC noise, and its effect and measurement”
http://www.quietpc.com/download/hp_white_paper.pdfThe regulatory noise levels/limits are not of much use for general office nosie levels where one is required to concentrate on particular tasks etc.!