Journal of New Music Research, Vol. 23 (1994), pp. 369-399 0929-8215/94/2304-369$6.00 © Swets & Zeitlinger Detection of Pitch in Random Acoustic Signals by Neural Networks Nicola Cufaro Petroni, Franco Degrassi and Guido Pasquariello ABSTRACT By means of a backpropagation neural network a model has been built which is able to distinguish between noises and tones endowed with a detectable pitch in a (computer simulated) random acoustic environment where the information carried by the signals is compressed to its essential part by the reduction of the Fourier transform into templates of 12 numbers used as inputs. It is found that a neural network able to detect a pitch is also able to recognize the presence of a residue pitch in the signals of complex tones where the first (or the first two) harmonic has been subtracted. Finally, the correlations between the concept of consonance and the presence of a detectable pitch in the superposition of pairs of complex tones are briefly investigated. 1. INTRODUCTION The ultimate aim of this research is to try to account for the emergence of the tonal sensitivity in the tighter connection possible with the physical phenomena of the sound. However, we must immediately acknowledge that the results accounted for in this paper describe only a very preliminary stage of this investigation and that, for the time being, we are not trying to build a psychological model for tonal relations: the aim of this paper is much more limited in scope and it is rather that of building a model to test the ability of a neural network in extracting some particular information from a particular random environment. This will account also to a test of what sort of information is really contained in the simulated random environment, so that this will also be a test to verify the hypotheses needed to build it. It is clear, from the previous remarks, that in this paper the emphasis will be on physics and information rather than on psychology and music, even if, in our opinion, this will shed some light also on the birth of a tonal sensitivity. In trying to approach an understanding of musical ideas about the tonal system there are different levels of investigation: pitch, consonance, keys, tonal relations, and so on. For the time being we will limit ourselves only to the first part of this sequence and we will try to investigate how much in the higher levels is Downloaded by [Universita Degli Studi di Bari], [Nicola Cufaro Petroni] at 04:39 03 November 2012