Abstract: This invention is an acoustic feedback peak elimination unit and has as its objective the elimination of unwanted acoustic resonance peaks, also called ring modes, inherent in an enclosed region where a sound amplifying system may be used. A number of separate units embodying the present invention may be used in cascade, each unit being adapted to handle a small frequency range of about an octave within the entire frequency range to be amplified, each such unit functioning at unity gain to eliminate a single feedback peak when present. In addition, the invention includes means for energizing an oscillator within its tunable frequency range so that a particular frequency may be introduced for tuning the entire sound system with desired precision.

Abstract: This invention relates to a ring buoy (life preserver) consisting of a toroid or doughnut-shaped ring of a plastic foam, preferably but not necessarily of polystyrene foam, provided with an integral tough, wear-resistant and weather-resistant outer film of flexible strong material and having within the buoy near the outer circumference thereof within the material a continuous ring of strong, rigid material as iron, steel or other material having desirable weight characteristics. At spaced intervals indented in the outer edge of such ring are a plurality of regions, such as four, free of the buoy plastic material and providing access to such ring, whereby rope may be affixed to the ring buoy, this usually being required by rules and regulations governing the construction of such buoys and the use thereof on boats and marine facilities.

Abstract: This invention relates to a system for masking conversation in an open plan office. A conventional generator of electrical random noise currents feeds its output through adjustable electric filter means to speaker clusters in a plenum above the office space. Each cluster has two speakers in a trigonal prism-shaped cabinet, symmetrically disposed about an axis of symmetry, oriented to be vertical. The speaker arrangement is such that, throughout the open plan office area, including below speaker clusters, the background sound energy level horizontally in the open plan office space has a generally constant value except for a modification which provides for a quiet region below a cluster. By proper spacing of clusters horizontally along the plenum region, transmission of background masking sound through an acoustic ceiling throughout an open plan office space, conversation in one region of the office cannot be distinguished at a distance of the order of about 15 feet or more.