1. An electronic device, comprising: a receiver configured to receive a stereoscopic moving image including a plurality of frames; a controller configured to: obtain a change in depth information of at least one object included in the stereoscopic moving image, calculate a summed depth value by summing depth values for a plurality of pixels in each of a plurality of pixel lines along a first axis direction in each of depth maps for previous and current frames, and produce a sound zooming factor in consideration of a difference between a maximum summed depth value for the current frame and a maximum summed depth value for the previous frame in the first axis direction; and an audio processor configured to apply the produced sound zooming factor to a sound signal corresponding to at least one speaker of a plurality of speakers outputting sound signals for the stereoscopic moving image.