Abstract: A method for estimating a partial discharge factor of a power semiconductor module which is capable of automatically estimating a partial discharge factor is provided using time-series data of a quantity of charge discharged during a partial discharge test. The method includes: a measurement step of applying, to the power semiconductor module, a test voltage pattern in which a voltage pattern changes, and measuring a quantity of charge that is due to partial discharge of the power semiconductor module; a feature quantity extraction step of extracting a plurality of feature quantities including at least a first feature quantity that is an average value of a quantity of charge in a first time period and a second feature quantity that is an average value of a quantity of charge in a second time period; and an estimation step of estimating the partial discharge factor based on the plurality of feature quantities.

Abstract: There are provided headphones and a speaker unit having proper acoustic properties and exhibiting excellent reproduced sound quality even in the case of providing air holes at a damping member. The headphones include a speaker unit having a diaphragm and a frame supporting an outer peripheral portion of the diaphragm, a housing configured to house the speaker unit, and a damping member made of a material exhibiting air permeability and attached to cover an opening of the frame through which a sound wave emitted from the diaphragm passes and/or an opening of the housing. The damping member has one or more air holes formed by removal of the material forming the damping member. A secondary damping member is attached to an annular edge portion defining each air hole, thereby reducing vibration of the edge portion.

Abstract: There are provided headphones and a speaker unit having proper acoustic properties and exhibiting excellent reproduced sound quality even in the case of providing air holes at a damping member. The headphones include a speaker unit having a diaphragm and a frame supporting an outer peripheral portion of the diaphragm, a housing configured to house the speaker unit, and a damping member made of a material exhibiting air permeability and attached to cover an opening of the frame through which a sound wave emitted from the diaphragm passes and/or an opening of the housing. The damping member has one or more air holes formed by removal of the material forming the damping member. A secondary damping member is attached to an annular edge portion defining each air hole, thereby reducing vibration of the edge portion.