Abstract: In a hearing device, such as a circumaural earmuff cup or a circumaural earphone cup, either of which comprises an earpad assembly in contact with the external ear, through which sound is conducted to the external ear for the purpose of providing at the eardrum a sound pressure having a prescribed ratio with respect to the sound pressure at a source, the invention comprising a predetermined sound leakage path through said earpad assembly, to reduce the variable in said ratio, that is customarily encountered caused by the variations in the shape of the external ear from one user to another and by variations in position and force of contact of the earpad resting against the pinna.

Abstract: A method and apparatus particularly adapted for alloying a coating on a steel strip. The invention uses an induction heating furnace to produce a galvannealed product. In particular, the operating frequency to the heating coils of the furnace is modulated to avoid a resonant vibration in the steel strip through the heating zone of the furnace. Preferably the invention comprises imposing a frequency modulation on the operating frequency of the power signal to the heating coils.

Abstract: In an ear muff intended for protection against excessive noise exposure, the passive means according to this invention automatically and continuously varies the amount of reduction provided for the sound arriving at the ear of the wearer; it retains substantially unaltered the performance of the ear muff for high sound levels, but effects a prescribed lesser value of sound reduction at low sound levels and maintains coherent phase relations between the sound waves arriving at the two ears as needed for reception of directional information.

Abstract: A non-contacting damping method and means for reducing vibrations in, and noise radiation from vibrating mechanisms, particularly saws and other mechanical members or materials with acoustically radiating surfaces that may be required to move with a substantially frictionless relation to the damping means is disclosed.

Abstract: A kaleidoscope includes three or four highly polished plain, front-surface mirrors assembled in the form of a prism with a cross section that is an equilateral triangle, a square or a rhombus with the angles between sides of 60.degree. and 120.degree., having a length 8 to 15 times the linear dimensions of its cross section. An optically opaque cylinder encloses the mirror assembly with opaque end caps providing alignment of the positions for the ends of the mirrors and electric light means for illuminating objects being viewed.

Abstract: A condom comprises inner and outer sheaths with the region between the inner and outer sheaths forming a fluid reservoir so that the inside of the inner sheath remains dry.

Abstract: Noise generation by machines having cam driven reciprocating elements is reduced in a machine wherein the cam-follower linkage comprises a double walled cam slot, a follower roller within the slot and spring means for moving the follower from the trailing wall to the leading wall of the cam slot.