5.13 Creative Room Acoustics - Foreign and Commonwealth Office FCO

Brief

The FCO proposed to cover one of their four courtyards with a glazed structure. To further enhance this space a new 9 by 9m, 5 storey office block was proposed to be erected in centre of the courtyard.

Having previously covered one of the smaller courtyards, acoustics was seen to be a significant issue.

Design Scheme

One the most important aspects when designing room acoustic finishes is to consider that all one is doing is adding the required level of fibrous or open celled material to a given space. It is therefore possible to be exceptionally creative when undertaking this process. 

Allies and Morrison’s proposal was therefore to clad the tower with acoustically absorbent fins 1. Such to assess the feasibility of this proposal, a 3D acoustic model of the spaces was formed 2. This model was used to assess the acoustic design of the fins 3 to 5 as well as the required levels of room acoustics treatments.

The results of the assessment indicated that providing the fins were 250mm deep, 25mm wide and at 750mm centres, the required reverberation time of 1.5 second would be complied with. Aesthetically, the design team considered the fin depth to be too deep. The metal structures supporting the roof were then proposed to also be acoustically clad thus adding more absorption area 6. This reduced the fin depth down to 140mm.