No woven curtain can replace double glazing or stop a night bus vibrating your floorboards. Yet a well-detailed heavy curtain remains the fastest way to remove harsh glass glare and soften mid-to-high frequency street noise.
ABSORPTION INSIDE VS. ISOLATION FROM OUTSIDE
Large expanses of glass—whether Victorian sash bays or modern patio sliders—act as rigid acoustic mirrors for frequencies above 500 Hz. When you draw a heavy curtain across a window, you immediately replace a hard reflective mirror with a deep, folded porous absorber. Inside the room, speech becomes warmer and television dialogue stops bouncing sharply off the glass.
For noise arriving from outside, curtains work differently. Because fabric is flexible and breathable, low-frequency traffic rumble passes right through it. However, tyres hissing on wet tarmac, pedestrian voices, and dawn birdsong sit between 1,000 Hz and 5,000 Hz. A dense multi-layer curtain hung with closed perimeter edges can shave 4 to 7 decibels off that high-frequency band—enough to make a noticeable subjective drop in sharpness.
LEFT PLAN: Standard finial pole leaves a 10cm air gap at top and sides.RIGHT PLAN: Curved return track seals fabric to the plaster 20cm past each reveal.
CURTAIN MEASUREMENT STRIPS: HOW FULLNESS AND WEIGHT INTERACT
Hanging a heavy curtain stretched completely flat reduces its acoustic absorption by almost half compared to hanging the exact same fabric with a 200% (2x) pleat gather. Folding the fabric creates deep pockets of varying air depth (from 20mm to 140mm off the glass), allowing the curtain to trap lower vocal frequencies.
FIVE QUIET JOINERY RULES FOR HANGING ACOUSTIC DRAPERY
Seal the window frame first: Before buying fabric, inspect the sash or casement perimeter. If you can feel cold draughts or slip a business card between the frame and seal, sound is pouring through that air gap. Apply EPDM rubber compression strips or brush pile seals first.
Choose a ceiling track or boxed timber pelmet: Sound waves rise through the gap between a curtain pole and the wall. A ceiling-fixed aluminium track or a simple timber pelmet box lined with felt closes the top chimney path.
Extend 20 to 30 centimetres past each side reveal: This gives the curtain enough overlap to seal against the plastered wall when closed, and allows the fabric stack to sit completely clear of the glass during the day so you lose zero daylight.
Specify interlining ("bump" or theatre molton): Instead of buying stiff PVC-coated blackout curtains that crinkle and reflect sound back into the room, ask a curtain maker to sandwich a heavy 300 gsm brushed cotton molton interlining between a breathable wool or velvet face fabric and a standard cotton lining.
Kiss the floor or wide window board: Stop the hem 5 millimetres off the floor or let it puddle slightly so air cannot rush underneath the bottom edge. Never hang an acoustic curtain that stops mid-wall above a radiator while leaving a 15-centimetre gap behind it.