One major challenge we faced was access to a laboratory. The thesis that was presented at Sorbonne University addressed primarily the perception of phonemic tones by means of drums (see figure 1). The mechanical basis helped explain the co-existence of tone and intonation in tone languages, as well as the intelligibility of speech in a tone language despite contextual modifications and outright losses of tone in connected speech. The thesis could have been published soon after its presentation in February 2000. However, the thesis addressed primarily the production and perception of phonemic tone. For it to constitute the foundation of hearing sciences, it was compelling to experiment and write up a comprehensive theory of hearing. In this regard, the principle of pitch regulation on the Yoruba drum does not allow for quantitative evaluation of the size of force exerted on the membrane through the tendons. To overcome this lack, it was necessary to conduct new experiments on strings. To that end, it was indispensable to design and build a special string tuner (fig. 2) for measuring the force that is the inherent property of the string as opposed to the force that is exerted externally to the string (usually called tension). Every other thing would yield a partial accomplishment; and there was no reason for it since the work at Sorbonne had laid out all the facts. The string data complemented the drum data in the thesis to produce a comprehensive theory of hearing, and established a mechanical foundation for hearing sciences on the basis of invariance. The detailed report in the book testifies not only to the complexity of the problems but also to the significance of invariance as a guiding principle in resolving deeply entrenched problems of human behaviour.
To overcome the laboratory problem, one bedroom in our London residence from where we operate was converted into a laboratory. Our director, formerly an architectural designer and building constructor, got all the work done. He also designed the string tuner for construction by Lines Guitars UK. The design of the string tuner allowed for sound recording without recourse to microphones. This provision enhanced noise control and facilitated stimuli acquisition during recording sessions.