TABLE OF CONTENTS Darkness falls over the vast auditorium and a thrilled murmur of expectation ripples across the audience. The pianist raises his hand, pauses briefly, and then lets it falls softly to the keys, whereupon you hear the first chord of the piece. You wince, because the pianist bungles his fingering; what should have been a melodious tonic triad in C major (C, E and G) accidentally included D#, resulting in excruciating discord.
At this point in time a member of the audience would probably care little about the auditory processing power of his or her own brain, or indeed its pertinence to the subject at hand. The fact remains, however, that there are a number of fascinating signal processing issues surrounding this little vignette that we will explore in some detail in this chapter; these explorations will serve us well throughout the remainder of this book and, if you have such an inclination, in your career as a practitioner of DSP.
The chord produced by the musician above clearly consists of four audio-range acoustic frequencies and their harmonics: middle C (262 Hz), D# above middle C (311 Hz), E above middle C (330 Hz) and G above middle C (392 Hz). Few individuals would have any difficulty in distinguishing this sound from that, say, of middle C played in isolation. But consider this: most people can also readily distinguish between the sound of middle C played on a piano and the same note played on a violin. This is...
