Two sound waves of the same frequency but slightly different amplitudes are heard simultaneously. The HUMAN PERCEPTION will identify:

Pitch is determined by FREQUENCY. Loudness is determined by AMPLITUDE. Same frequency = same pitch. Different amplitudes = different loudness (volume). So the two sounds would have the same pitch but different volumes — perhaps sound like the same note played by two different instruments at different volumes (though timbre would also differ in real instruments, this question keeps frequency fixed).