Anti-eavesdropping window structure

US4829729A · kind A · utility

Assignee

• Flachglas Aktiengesellschaft · DE

Inventors

• Paul Derner · Gelsenkirchen, DE
• Peter Reichmann · Gelsenkirchen, DE

Key dates

• Filing date: Apr 3, 1987
• Grant date: May 16, 1989
• Expiry date: Apr 3, 2007

Classification

• Technology area (CPC E): Fixed Constructions
• CPC primary: E06B3/6707
• WIPO field: Civil engineering
• WIPO sector: Other fields

Abstract

An anti-eavesdropping window structure in which the inner and outer panes, separated by a spacer frame have thickness d and D such that D/d is at least equal to 1.5. The space between the panes is filled with a gas mixture having a density in excess of that of air and a body-sound generator applied directly to the outer pane generates thermal noise over a frequency range of 200 to 3000 Hz to superimpose a level of such noise of at least 20 dB on transmitted sound.