About the Book
About the Book
Thirty-six years ago, the seed that has developed into Sound Sources: The Origin of Auditory Sensations was planted.
It started as a trivial experiment with frequency contours of naturally-produced tone-bearing monosyllabic words in Yoruba. Hardly did I know that the project was a gateway to the turning point in the history of hearing research. It has been a very long and hard road. I drew a lot of comfort and courage to continue from the support of lovers of science and stimulants to scientific progress. Despite outright oppression by opposers, the work survived to provide a foundation for a new generation of scientists (see figure 1).
Figure 1: Sound Sources: The Origin of Auditory Sensations.
The research is founded on the hypothesis which stipulates that an acoustic system cannot transmit what it does not possess. Thus, a sound source (or any acoustic system) will generate auditory qualities according to its physical, chemical, and mechanical properties (among many others). Therefore, if we could detect the property of the sound source that underlies a given sound quality, the property would, invariably, be invariant with the associated sensation since its presence or absence in the sound source implies presence or absence of the quality in the sound. This approach has proved to be very successful. Its primary achievement is the unmatched contribution of the first invariant in hearing research at the mechanical level of sound production in nature. The impact of this break-through is unfathomable. It can be truly appreciated only from the standpoint of a comparable scientific development.
To illustrate, take, for example, pre-historic conception of a flat earth supported by elephants standing on a sea-turtle. Outside the incredibility of the conjecture, that conception of the earth’s support in space creates a very false picture of the reality. It aroused the fear of venturing out too far and falling off the edge of the flat earth to one’s destruction. However, although the conception of a round earth “hanging on nothing” might have been equally difficult to imagine until the theory of gravity set things straight, knowledge of the truth has helped mankind make the best use of our planet, whether we travel on it or fly around it.
In a similar way, pre-historic knowledge of mechanical physics of materials have condemned hearing sciences to exploit frequency of vibration in the hope to understand hearing. However, if the physical link between the sound source and the ear were removed (as in the case of pre-historic support for the earth in space), we would have accurate knowledge of the process in hearing, that the physical link between the excited object and the organism in terms of perturbations in the medium is not necessary for the ear to experience the sensation of sound. The removal of the physical link would lead us to correctly appreciate how wonderfully we were made to perceive, by sound, the environment in which we live. Besides, it would help us device new theories to explain how the ear apprehends vibrating bodies to arrive at auditory attributes. Such knowledge will, indeed, contribute towards remedies for sufferers of auditory handicaps.
Thus, the discovery of a mechanical invariant in pitch production in nature is the pride of EAR Laboratory. This feeling is shared with the world in Sound Sources: The Origin of Auditory Sensations. We proudly acclaim it the second step in auditory psychophysics after the Pythagorean string ratio theory of musical pitch intervals. Pythagoras discovered a functional relationship between string ratios and pitch intervals. It did not address pitch itself, but pitch intervals. Sound Sources (for short) traces out the property of the string and other sound sources that underlies the sensation pitch, and reduces all the variables to one simple mechanical law. It outlines an unprecedented approach to scientific study of speech, music, and hearing.
Thus, although Sound Sources shuts out philosophical, physical and mathematical speculations in hearing research, it is not a work that I have produced for people to know what I know or do what I did. Rather, it is intended to serve as a foundation and act as a stimulus for a new generation of scientists to exploit to know what I do not know and conduct further experiments to do what I could not do. As the name Implies, it is a foundation for theories of music, speech, and auditory analysis. In it there are no guesses, no assumptions, no philosophy, no extrapolations nor idealizations. It is direct, realist, and covers mechanical principles of sound production and its perception. It takes off where Pythagoras left off in the 6th century B.C. Therefore, current psychoacoustic and mechanical theories of hearing without invariance belong to the pre-Pythagorean era which is more than 2,500 years behind our day.
I could have called it The Mechanical Foundation. However, the title would limit the scope of investigations to the finding of the mechanical invariant property of the sound source. Rather, the work goes a lot further to enunciate the concept of sound from the standpoint of sound production in nature. The ecological, conception of sound establishes the hitherto elusive link between the organism and sound sources. Thus, the circuit from sound production, transmission and perception is completed, showing how organisms produce sounds and apprehend the environment by eye, and more so by ear.