Since the room acoustic parameters in ISO 3382-3 were published, there have been various international attempts to classify offices achieving different values. However, recent summaries of acoustic satisfaction demonstrate little correlation with the room acoustic parameters that may drive the design. A new case study illustrates significant differences in acoustic satisfaction for people on two different floor plates within the same building; these have very different workplace design, but have almost identical parameters according to ISO 3382-3.A new approach is proposed to assess acoustic conditions within activity-based working (ABW) offices. The method to characterise the acoustic environment in terms of Liveliness is used to determine appropriate noise levels for different activities. A matrix of signal-to-noise ratios are postulated to account for source level vibrancy and receiver sensitivity. This enables a design framework for the in-situ attenuation of speech between workstations, Dn, A, s. From the in-situ attenuation requirement, the layout design can be developed accordingly. This method identifies conflicts between different types of use or activity where there is insufficient attenuation between them. This informs the workspace designer where enhanced in-situ attenuation can improve the acoustic conditions for occupants.