Abstract: A sound field correction apparatus that corrects a sound field characteristic by supplying a measurement signal used for measurement purposes to drive a plurality of speakers arranged at arbitrary positions to reproduce the measurement signal and receiving a collected sound signal obtained by collecting the sound reproduced from the plurality of speakers with a sound collector disposed at an arbitrary listening point is disclosed. The sound field correction apparatus includes: a measurement signal supplier, a receiver, a delay calculator, a sound pressure level difference calculator, a delay correction value calculator, and a gain correction value calculator.

Abstract: To provide a lubricating material suitable for use in space or vacuum, light in weight, low in friction coefficient and long in life time, oxidation treatment is effected on the surface of titanium or titanium alloy substrate before a solid lubricating film is applied to the substrate. The formed oxide (Ti.sub.2 O) can strengthen bonding force between the substrate (Ti) and the solid lubricating film (e.g. MoS.sub.2).