2.2.5  Acoustics

The noise levels generally shall not exceed NR35 in offices; otherwise acoustic properties and performance shall be in accordance with Part E of the building regulations.

External noise levels due to the engineering services should not exceed a level of 45 dB(A) at 5.0 metre away from and directly in front of, any discharge or intake grille, ventilation, louvre, external building wall or roof, or any externally mounted plant items..

All office areas should be provided with an appropriate level of confidentiality, privacy and noise control.

Personal screening to open plan office areas should not adversely affect the use of the space or interaction between personnel by voice or sight.

Acoustic reduction to cellular office areas should be to an appropriate level taking into account ambient noise levels and the use of the space. Confidentiality is referred to specifically on the Zone Data Sheets and by department and not less than the minimum standard defined in BS8233.

In terms of the application of this standard, the assessment of confidentiality can be equated to a privacy level whereby a normal voice would be virtually inaudible and a raised voice would be audible but not intelligible. The Contractor will propose a solution to achieve the Authority's objectives as a basis for discussion and agreement prior to construction and the measurement methodology for assessing compliance is to be agreed between the parties in conjunction with the ITA however the initial basis of such methodology may be defined in acoustic practice as a privacy factor of 'Very Good' calculated as the average sound insulation, dB(dw) and the ambient noise level, dB (LAeq).

Privacy Factor as the sum of ambient internal noise LA in the receiving space and the Weight Level Difference of the separating construction Dw (Very Good = 80), is measured in accordance with BS EN ISO 140-4:1998 (Dw is likely to be 5dB less than the element laboratory rating Rw).

Areas of high noise levels or constant 'clutter' may require additional care and use of absorbent finishes within the design to ensure a satisfactory working environment.