A signal processing device includes: an obtainer that obtains sound data; a pitch controller that controls pitch of the sound data obtained to increase the pitch by a factor of n (a real number greater than 1); an extractor that extracts frequency components of at least 20 kHz which are included in the sound data whose pitch is controlled; an adder that adds the frequency components extracted to the sound data obtained; and an outputter that outputs sound data to which the frequency components extracted are added.