Abstract: The invention concerns an ultrasonic detection device intended to detect the presence of foreign bodies, on the surface of a window comprising a first sheet having a first thickness, comprising a transducer co-operating with a first face of said first sheet, said transducer being able to emit an ultrasonic signal of frequency f.sub.t and also able to receive a reflected ultrasonic signal on a second face of the first sheet, the variation in said reflected signal being representative of the presence or absence of foreign bodies on said second face facing said transducer. This device is characterized in that the frequency f.sub.t is selected to satisfy the following equation:f.sub.K /100.ltoreq..vertline.f.sub.t -f.sub.K .vertline..ltoreq.f.sub.K /10where f.sub.K =K.

Abstract: The composite wall comprises a first sheet and second sheet separated by an intermediate layer as well as an ultrasonic detection device placed on a face of said second sheet and comprising a transducer element able to emit an incidental ultrasonic signal of frequence f, and able to receive an ultrasonic signal reflected on a face of said first sheet. The intermediate layer comprises at least facing the transducer element, an inserted element whose two faces are respectively in close contact with the first and second sheets. Further, the frequence f of the transducer element satisfies the following relationships:f.apprxeq.K.sub.1. V.sub.1 /2e.sub.1 .apprxeq.K.sub.2.V.sub.2 /2e.sub.2 .apprxeq.K.sub.3.V.sub.3 /2e.sub.3where K.sub.1, K.sub.2 and K.sub.3 are defined integers, e.sub.1, e.sub.2 and e.sub.3 are respectively the thickness of the first sheet, the second sheet and the inserted element, and V.sub.1, V.sub.2 and V.sub.

Abstract: The invention concerns a window including at least a first sheet (16), a second sheet (18), said sheets being joined together by a connecting layer (20), characterised in that it also includes an ultrasonic device (12) placed between said sheets (16,18) and co-operating directly with a first face (24) of said first sheet (16) to detect the presence of foreign bodies on a second face (26) of said first sheet (16) opposite said first face (24), said device (12) comprising a transducer (28) able to emit, via a transmitting/receiving face, an incidental ultrasonic signal of wavelength .lambda. in said first sheet (16), the thickness of said first sheet being equal to K..lambda./2, where K is an integral number, and said transducer being able to receive, via said transmitting/receiving face a reflected ultrasonic signal representative of the presence or absence of said foreign bodies to generate a detection signal.