Ajay Bijli residence, Vasant Vihar

A residence in Vasant Vihar, designed for Mr Ajay Bijli, Owner of PVR Cinemas, by a celebrated French architect. The architecture was not the problem; the location was. The property sits close to IGI Airport, and while T1 and T2 contribute their share, it is the Cargo Terminal that shapes the noise the bedrooms actually receive. Jumbo freighter sorties are concentrated at night and before dawn, and their energy sits low in the spectrum — where glazing has the least to give.

Three bespoke window assemblies, manufactured in Italy and specified at design stage for high Sound Transmission Class (STC) performance per ASTM E90 methodology, had begun to exhibit audible resonant flutter under sustained low-frequency loading. That is the signature of mass-air-mass resonance: the panes and the air between them behave as a sprung mass, and at the frequency where that system resonates the assembly's insulation drops away. The freighter movements were exciting the bedroom envelope beyond the glazing's designed coincidence frequency.

There was a second path, and it had nothing to do with the windows. The ground-floor diesel generator (DG) set shared a common structural column and slab continuity with the master bedroom wall, so its vibration travelled into the habitable envelope through the structure itself — a textbook flanking-transmission scenario of the kind characterised under ASTM E497 and ISO 10848 flanking-path protocols. No glazing specification would have touched it.

• An airborne coincidence-dip failure in the glazing, at the frequencies freight aircraft produce rather than those of ordinary traffic.
• A structure-borne flanking path from the DG set into the master bedroom wall, by way of a shared column and continuous slab.

The glazing was re-engineered in collaboration with the AIS Glass engineering teams: a laminated and decoupled assembly with revised interlayer damping, moving the resonance away from the frequencies this site actually delivers and adding loss where the original build had little. That is the ordinary business of acoustic glazing — pane thicknesses, interlayer and cavity chosen against the noise in front of them rather than against a headline figure.

The flanking path was treated separately, with vibration-isolation detailing at the generator to sever the bridge between the DG set and the superstructure. Both paths had to close for either to be worth closing.

Both transmission paths closed, and the bedroom envelope performing as it was drawn to — with the architecture untouched.

The case is a plain argument for post-occupancy acoustic forensics. Neither failure was visible on paper: the windows were correctly specified for a general noise condition and wrongly specified for this one, and the generator was never part of the glazing conversation at all. Diagnosing a house that has already been built is a different exercise from designing one, and for premium residences inside an aviation noise contour it is usually the exercise that is needed. See consultancy for how that survey work runs.