Sound insulation mainly depends on profile structure, glass configuration and sealing workmanship, measured by weighted sound reduction (Rw) graded by GB/T 8485-2008 (top grade 6 = 45 dB). Key factors: glass — insulating glass blocks high-frequency noise (speech) but weak on low; laminated glass's PVB absorbs mid-low frequencies (traffic); laminated-insulating combos are best (e.g. 5 mm laminated + 12A insulating). Profile — multi-chamber thermal-break aluminium (70 series+) blocks the sound bridge; EPDM gaskets outlast PVC for lasting sealing. Installation — dry installation (foam filling) avoids sound leaks; weather-resistant sealant gives a second seal at the frame-wall joint. Practical advice: urban homes choose laminated-insulating glass with Rw ≥ 40 dB; street/viaduct prefer laminated glass with wall ≥ 1.8 mm; require a test report at acceptance to avoid 'fake system windows'. No single material fully insulates — integral design is needed.