Photographing Voices There is more to sound recording than just getting speech and other sound onto tape. ... energy intensity at each frequency and instant is proportional to the blackness or thickness of the bar. ... The a#39;contoura#39; form on the right is a graphic evaluation obtained by connecting up points of equal blackness on the moist print. ... The technique for recording such voice spectra or voiceprints was developed by L.G. Kersta, and involves recordingthe voice intensities atanbsp;...