Abstract: Acoustic attenuation materials are described that comprise outer layers of a stiff material sandwiching a relatively soft elastic material therebetween, with means such as spheres, discs or wire mesh being provided within the elastic material for generating local mechanical resonances that function to absorb sound energy at tunable wavelengths.

Abstract: Electronic education systems generally includes a central computer, a display unit, and various student terminals connected to the central computer by a data transmission network. The network transmits data to and from the central computer for analysis, the data includes students' task and their response. Such a system is relatively expensive, and is not portable. This invention provides an electronic education system for evaluating responses from a group of students to a set of multiple choice questions. Each of the questions having a maximum of x choices. The system includes at least one IR transmission device for transmitting a plurality of IR signals to a console, which includes a processor for analyzing the responses, a memory for storing the multiple choice questions and corresponding answers, output means for outputting data to a display device, and receiving means for receiving the IR signals.

Abstract: Acoustic attenuation materials are described that comprise outer layers of a stiff material sandwiching a relatively soft elastic material therebetween, with means such as spheres, discs or wire mesh being provided within the elastic material for generating local mechanical resonances that function to absorb sound energy at tunable wavelengths.

Abstract: Acoustic attenuation materials are described that comprise outer layers of a stiff material sandwiching a relatively soft elastic material therebetween, with means such as spheres, discs or wire mesh being provided within the elastic material for generating local mechanical resonances that function to absorb sound energy at tunable wavelengths.

Abstract: A one-way or single-channel communication network utilizing electromagnetic radiation signals of a fixed single or narrow-band frequency in free air space consists of a plurality of transmitters and a central receiver in which each message is encoded in a wave train and is tagged with a sender identity (ID). The central receiver, which can be a single unit or a plurality of units connected in cascade, detects the messages in the free air space and send them along to a central processing unit (CPU) for message handling.