What type of alarm system is designed to detect the sound of breaking glass?

The audio discriminator is specifically designed to detect the sound of breaking glass, making it the correct answer to the question. This type of alarm system features sensors that can differentiate between different sounds and recognize the unique frequency pattern produced by glass breaking. This capability allows it to alert security personnel or trigger an alarm system when an intrusion is likely occurring due to the sound of shattered glass.

Other systems, such as door/window contacts, are primarily focused on detecting the opening orclosing of doors and windows, and motion detectors are mainly used to identify movement within a designated area. Foil systems typically involve a conductive material placed on a surface to create a circuit that signals when disturbed, rather than detecting specific sound frequencies. Thus, while these systems serve important roles in security, they lack the specificity required to detect glass breakage like an audio discriminator does.