A control device includes a first communication circuit, a microphone, and a first control circuit. The first control circuit: acquires background noise in the room through the microphone and calculates a signal level of the background noise; transmits, to a playback device, a first control signal directing playback of a first test signal through a loudspeaker; acquires the first test signal through the microphone and calculates a signal level of the acquired first test signal; estimates a signal level of a second test signal using the signal level of the first test signal as a reference; increases a set value of a sound volume of the second test signal when a signal level obtained by subtracting a predetermined value from the estimated signal level of the second test signal is less than or equal to the signal level of the background noise; transmits, to the playback device, a second control signal directing playback of the second test signal through the loudspeaker; acquires the second test signal through the microphone, calculates a frequency response of the room, and calculates a correction coefficient based on the calculated frequency response; and transmits a third control signal including the calculated correction coefficient to the playback device.