Abstract: A foldable electronic device includes a first and second housings foldably coupled through a hinge, a flexible display supported by the first and second housings, a first speaker disposed in the first housing and a second speaker disposed in the second housing. The electronic device determines first and second states in which the first and second housings unfolded or folded. The electronic device controls sound frequency characteristics of the first and second speakers to have first sound frequency characteristics with the electronic device being in the first state. The electronic device controls sound frequency characteristics of the first speaker to have second sound frequency characteristics with the electronic device being in the second state. The electronic device may also control sound frequency characteristics of the second speaker to have third sound output frequency characteristics with the electronic device being in the second state.

Abstract: An accelerator sensor that is mounted on an engine block may be used to detect vibration of a compression ignition engine, and the detected vibration signal is analyzed to determine the combustion timing of the engine. A method for detecting combustion timing may include measuring a block vibration signal generated in a combustion process of an engine, setting up a frequency area that is to be analyzed in the block vibration to divide the frequency area into wavelet scales, executing continuous wavelet transformations of the divided wavelet scales to extract respective result values thereof and to calculate differences between former result values and latter result values, comparing the calculated difference value with a predetermined value to store crank angles of pertinent timing if the calculated difference values exceed the predetermined value, and averaging the stored crank angles to determine combustion timing in a case that all wavelet scales are processed.

Abstract: An accelerator sensor that is mounted on an engine block may be used to detect vibration of a compression ignition engine, and the detected vibration signal is analyzed to determine the combustion timing of the engine. A method for detecting combustion timing may include measuring a block vibration signal generated in a combustion process of an engine, setting up a frequency area that is to be analyzed in the block vibration to divide the frequency area into wavelet scales, executing continuous wavelet transformations of the divided wavelet scales to extract respective result values thereof and to calculate differences between former result values and latter result values, comparing the calculated difference value with a predetermined value to store crank angles of pertinent timing if the calculated difference values exceed the predetermined value, and averaging the stored crank angles to determine combustion timing in a case that all wavelet scales are processed.