Abstract: A fast and economical method for speeding up an audio signal without changing pitch can be accomplished by eliminating unneeded information from an audio signal. First, the signal is divided into chunks (frames or subframes), on which a mathematical manipulation such as a Fourier transformation is performed to identify the amplitudes of the componenet sinusoids (sines and cosines). These absolute values of the sine and cosine amplitudes for each frequency are averaged together, and the highest value(s) represents the signature, or dominant frequency/frequencies. The dominant frequency/frequencies or signatures from one chunk are compared to those of the next, and when identical the latter unit is marked as redundant. The final step consists of discarding redundant chunks from the original data, thus providing a shortened signal for replay. The pitch will not change because the only modification to the original signal was the elimination of redundant data.

Abstract: A ceramic core for use in the investment casting of metals includes, prior to sintering, about 80 w/o to about 86 w/o of a ceramic filler material and about 14 w/o to about 20 w/o of a binder material. The ceramic filler material includes about 66 w/o to about 95 w/o Al.sub.2 O.sub.3 particles, about 1 w/o to about 20 w/o Y.sub.2 O.sub.3 particles, about 1 w/o to about 5 w/o of a grain growth inhibiting agent, and the balance a carbon-bearing fugitive filler material. Subsequent to sintering, the ceramic core has a microstructure characterized by the presence of substantially unreacted Al.sub.2 O.sub.3 particles having a polycrystalline composition consisting essentially of 3Y.sub.2 O.sub.3.5Al.sub.2 O.sub.3 on the surfaces of the Al.sub.2 O.sub.3 particles.