we can say that its loudness is 65 phons. The perceived loudness at 1000 Hz is the reference point for defining the equal loudness curve through that point, so the numerical value of phons and dB is always the same at 1000 Hz. Finally, we could say that sound C at 65dB is the loudest of the four sounds since it shows the greatest displacement above the 60 phon curve. From this graph, we cannot determine what that phon level is; that would require experimental comparison with 1000 Hz tones.