It is difficult to determine the composition of aperiodic sound phenomena, particularly those which vary rapidly with time, as, for example, speech sounds. The methods of automatic electric analysis cannot be applied directly because of the time required. The graphic or mechanical Fourier analyses cannot be recommended because a great number of single analyses must be carried out for aperiodic processes. A very clear idea of the sound composition as a function of time is obtained when the separate octave ranges of the sound processes are recorded oscillographically by means of filters. The result of such oscillographic investigations of speech sounds is described. The oscillograms very clearly show the different harmonic and inharmonic components of speech sounds. Conclusions in regard to the voice theory are drawn from the oscillograms.