Every tone has a frequency and an amplitude. Change the frequency of the tone from 100 to 200 Hz. The pitch of the tone that you hear should increase.
Then change the amplitude of the tone from 0.5 V to 0.25 V. The loudness of the tone that you hear should decrease.
Pitch is the perceptual correlate of frequency. Loudness is the perceptual correlate of frequency. Frequency an amplitude are the physical attributes of sound. Pitch and loudness are the way in which these attributes are perceived by the auditory system.