To adjust the effects of ambient noise, we can:

  alter the level of noise break-in from outside

  control noise from fixed mechanical equipment and machinery associated with the building

  reduce or increase the level of reverberation within a room

  introduce masking noise to cover disruptive ambient sound or create more non-disruptive ambient sound

This chapter aims to provide guidance on achieving speech privacy and reducing disturbance for the office worker.

Normal speech from one person at 3 ft (1 m) would be around L_Aeq 57 dB, while raised speech would be around L_Aeq 65 dB. Within open-plan offices, speech disturbance can be controlled to a reasonable standard where the noise level from speech reduces to below L_Aeq 48 dB at a distance of 13 ft (4 m). This distance can be reduced when the workers face away from each other. Therefore

  Two workers face-to-face, 13 ft (4 m) apart, normal speaking: < 48 dB criteria achieved.

  Two workers back-to-back, 6 ft (2 m) apart, normal speaking: < 48 dB criteria achieved.

At closer distances, or with higher speech levels, additional treatments would be required, e.g., barriers or noise masking.

9.2.4 Noise from maximum noise events, rain noise, and lift/elevator noise

In instances where there is a preference for natural ventilation, the L_Aeq and L_Amax levels for external sources should be relaxed by +5 dB.

9.2.5 Internal doors and openings

Sound transmission via external glazing elements between office spaces is possible. With regards to horizontal transmission, mullion specification should be set as follows:

  group office space to group offices spaces: min D_nF,n 45 dB

  group to withdrawn or private office space: min D_nF,n 53 dB

  withdrawn/private office to withdrawn/private office: min D_nF,n 53 dB.

The basic performance requirement can usually be achieved with the inclusion of an expanding spray foam or foam pad within a boxed mullion. The enhanced performance requirement can usually be achieved with the inclusion of two foam pads separated by a 100 mm gap within the boxed mullion.

9.2.7 Noise masking

It is often necessary to introduce background noise into an office space to improve speech privacy and reduce disturbance, particularly within open-plan offices. Electronic noise-masking systems can be used to help achieve required continuous, unobtrusive background noise levels that mask or cover intrusive sound.

Open-plan spaces: masking levels of between L_Aeq 45–48 dB are considered optimal.

Enclosed spaces: masking levels of between L_Aeq 38–42 dB are considered optimal.

  Try to adopt floor layouts that place ancillary space and non-noise-sensitive rooms along the façade most exposed to noise.

  Consider placing noise critical spaces, e.g., video conferencing rooms within central core areas.

  Consider layouts with central courtyards, to provide optimum natural light and ventilation while limiting external noise exposure.

  Place office space that can tolerate higher internal ambient levels along façades that are exposed to greater continuous ambient noise (e.g. road noise).

9.3.2 Control of internal noise

2)  Introducing areas where the ceiling height drops between groups or along circulation areas can reduce sound transmission around the space.

3)  Floor-to-ceiling heights should not exceed 11.5 ft (3.5 m). Acoustically absorptive ceiling are preferable, with a minimum absorption coefficient of ά_w 0.9.

4)  Acoustically absorptive dividers should not exceed a height of 3 ft (90 cm) from ground level. Allowing for some eye contact increases worker awareness of fellow workers and reduces prevalence for loud speech that may occur when a sense of privacy is offered by divider panels.

5)  Use of carpets or carpet tiles is preferred, as this will help reducing noise buildup from footfall and chair movement noise. It will also reduce impact sound transmission to lower rooms. Finishes with a minimum ΔL_w of 21 dB are preferable.

6)  Placing acoustically absorptive panels on walls will help reducing room reverberation. For both wall panels and freestanding panels, a minimum absorption coefficient of ά_w 0.8 is suggested.

7)  Freestanding acoustic divider panels between workstations should be as close to the workstation as possible, not placed halfway between two workstations. Glazed or Perspex vision panels should be considered for panels which are above 3 ft (90 cm) in height. Barrier effects from divider panels will be improved if they form a continuous barrier around a workstation and gaps around freestanding panels are avoided.

Suggested design consideration for reception areas are:

  Locate the reception desk away from intrusive noise sources, e.g., vending machines, foyer cafés, lifts, mechanical equipment.

  Separate reception desks from seating areas so receptionists can talk on the phone without being understood by visitors, while visitors can talk quietly amongst themselves without being overheard. Separating distances of 13 ft (4 m) or greater are optimal. Distances of more than 32 ft (10 m) should be avoided so that the receptionist can still attract a visitor’s attention.

  Discourage waiting next to the reception desk, to reduce disturbance for other guests or when telephone calls are being taken. Place company literature/visual displays or focal points away from the reception desk.

  Introduce background noise to help create privacy if reception areas are found to be too quiet, i.e., an active noise masking system.

  Do not place small meeting rooms and offices, with glazed walls and doors, directly off of a reception area. This can be problematic where confidentiality is a major concern.

Where floor or ceiling through ventilation/heating is taken under a separating wall, it is necessary to include a cross-talk attenuator on either side of the partition. Attenuators which are between 19 in (500 mm) and 39 in (1000 mm) should be detailed for either side of the partition.

Note: Where privacy is of paramount importance, such details should be avoided.

The following recommendations should also be considered:

  Use surface-mounted electrical and computer sockets rather than cutting the plasterboard on office walls.

  Run mechanical and electrical services along corridors; avoid running services over the top of walls that separate acoustically sensitive rooms.

  Avoid running suspended ceiling grids over the top of partitions designed for acoustically sensitive rooms. Even with acoustic baffle, details above ceiling grids can allow for some sound transmission.

  Avoid the use of glazed partitions or partially glazed partitions for walls that separate rooms where privacy is important.

  Incorporate framed doors, glazed or solid core, in the design of rooms where privacy is important.

  Avoid the inclusion of demountable partitions in the design of boardrooms, executive offices, private working offices, and private meeting rooms.

General Services Administration (GSA) (2011) Sound matters – How to achieve acoustic comfort in the contemporary office. Washington, DC: GSA Public Buildings Services.

Central Computer and Telecommunications Agency (CCAT) (1994) Management of acoustic noise (IT infrastructure Library). London: HMSO.

Irish, M. (2012) Acoustic design assessment, office development. Unpublished technical report, RMP Acoustics, Edinburgh.

Shield, B. (2009) Review of research on office acoustics, a report for the Association of Interior Specialists. London: AIS.

Veitch, J. A., and Naevia, M. (2003) Acoustic satisfaction in open plan offices: Review and recommendations. Ottawa: NRC-CNRC.