0Executive summary

A two-room recording studio (Control + Live/VO) plus a service zone, in a raw concrete basement shell. The concrete + block structure is excellent isolation mass — the work is decoupling, sealing, and acoustic treatment, not adding mass. With the designed treatment both rooms meet their acoustic targets; isolation is a box-in-box on a floating floor.

1The space (locked reality)

• Geometry: reproduced 1:1 from the architect's DXF and independently QC-signed. Layout: Service (west) · Control (centre) · Live (east) · entry south off the staircase.
• Ceiling is MULTI-LEVEL: tall ~3.97 m over 79% of the area, dropping to a ~2.85 m bay at the street/window edge. The live room is stepped (≈2 m of low ceiling at the street, then tall). Control sits in the tall zone.
• Materials: board-formed concrete + concrete block walls (good mass); raw concrete ceiling slab with drop beams; exposed conduits, pipes and rebar.
• Conditions to fix: uneven floor (level first), wall cavities (fill + build an even decoupled inner leaf), fireplace recess to demolish + fill, clerestory windows to seal.
• Boundaries: North = street · fireplace wall = party wall to another concrete building · West = new closing wall to a neighbour's meeting room · Above = occupied floor (basement → impact isolation) · South = stair + the stairwell ventilation fan.

2Ceiling heights — the step

This is RAW scan data in the scanner's own orientation — NOT the plan frame (it is rotated vs the drawing and covers area beyond our space). It was used only to derive the per-room ceiling heights, which are shown on the mm-accurate DXF plan above. Blue = low ~2.85 m (street/window bay), red = tall ~3.97 m; step offset ≈ 2 m.

3Modal & geometry

Both rooms share the 39.3 Hz length mode. Bass traps are fixed/always-on.

3bNon-parallel (splayed) walls — LF & flutter recomputed

Parallel surfaces stack standing waves; bass traps damp but don't un-stack them. Splaying the inner-leaf walls + sloping the ceiling spreads the modes (verified by a numerical eigenmode solve — the rectangular formula can't model splay).

Sheets A-301 / A-302 — control-room non-parallel walls (plan) and VO stepped ceiling + sloped inner leaf (section). Council-reviewed, 1:50 @ A3.

Design: both critical rooms get non-parallel side walls + a sloped decoupled ceiling, combined with the fixed bass traps. Cost ~0.2 m avg width; RT60 still passes.

4Reverberation & treatment (Eyring governs)

Bare concrete shell ≈ 5 s. Treatment gap: control ~29 m²sab (21 at 125 Hz), live ~18 (13 at 125 Hz).

5Isolation / STC & build-up

All boundaries clear field target with margin. View glass ≤1.5 m² → composite ≥STC 59 (it is the weakest element). Floating floor = standard (the noise source is the fan, not a generator): RC ~75–100 mm or ply on EPDM/rubber, 25 mm perimeter gap, zero rigid bridges.

6Preliminary quantities

Pricing pending Syria/Levant sourcing.

!Blocked / needs input

• BLOCKED HVAC & background noise (NC). Needs the stairwell-fan recording (on/off) + the chosen HVAC unit's specs. Site data only the client/operator can supply.
• refine Exact ceiling step offset → scan↔DWG registration.
• confirm Client sign-off on the RT/NC/STC targets.
• next Treatment layout (needs monitor positions), priced BOQ, construction documents.