Abstract: An audio processing device includes an input terminal to input an audio signal and a peak shift filter. The peak shift filter increases sound pressure with a first center frequency in the input audio signal as a first peak, and shifts the first center frequency between a preset lowest frequency and a preset highest frequency.

Abstract: Loudspeakers of plural channels are used as microphones to convert a test sound generated at a listening point into corresponding electric signals respectively. Moments of arrival of the test sound at the loudspeakers are detected in response to the electric signals respectively. Desired delay times for audio signals of the plural channels are calculated from the detected moments of arrival of the test sound at the loudspeakers. Volume levels of the electric signals are detected. Desired volume levels for the audio signals are calculated from the detected volume levels. The audio signals are delayed by the desired delay times respectively and volume levels of the audio signals are controlled at the desired volume levels respectively to get processing-resultant audio signals of the plural channels. The processing-resultant audio signals are fed to the loudspeakers respectively.

Abstract: An aluminum evaporator including a refrigerant tube and fins with a hydrophilic surface is prepared by forming a chemical coating over the surface of its components as assembled into a product or before fabrication, and thereafter forming a hydrophilic layer over the coating by treating the resulting components with a solution of silicic acid, silicate or colloidal silica.

Abstract: Colored aluminum powder is prepared by immersing finely divided aluminum in a weak alkali solution maintained at a temperature of 50.degree. C. to the boiling point of the solution and having a pH of 8 to 12, said solution containing a salt of iron, nickel, cobalt, zinc or copper, and at least one aliphatic amine having a chelating ability for the metal salt, to form a composite film which consists of a hydrated aluminum oxide and a hydrated oxide of the metal, and separating the aluminum from the solution.