A second housing 200 is capable of moving in a direction in which the second housing covers one surface of a first housing 100. Oscillating elements of an oscillating element group 400 are arranged in a matrix and oscillate sound waves outward from the one surface of the first housing 100. A control unit controls the plurality of oscillating elements. A sound wave sensor constitutes the same matrix as the plurality of oscillating elements and detects sound waves having a specific wavelength. The detection results of the sound wave sensor are output to the control unit. A frame body holds the plurality of oscillating elements and the sound wave sensor. The control unit oscillates sensor sound waves having a specific wavelength outward from at least one of the oscillating elements. The control unit determines that the second housing 200 covers the one surface of the first housing 100 when the sound wave sensor detects the sound waves having the specific wavelength.