Abstract

The wave propagation behavior in spiral cavity of a conch shell is studied. A conch shell consists of a spiral inner cavity where if excited by lip-vibration, a highly resonating sound with harmonic modes is produced. In order to understand how sound is generated in a conch shell, we used X-ray tomography scans to model the shell’s unwrapped inner cavity and measured how well the model matches the experimental data. Experiments were carried out in a semi-anechoic chamber where the conch shell was played using: (i). Lip-excitation (ii). Loudspeaker sine-sweep excitation and (iii). Excitation using an electro-pneumatic
transducer. The recorded sounds were analyzed in terms of their frequency components and directivity of the emanating sound. Moreover, we approximated a shell’s inner spiral cavity to a straight tube based on the X-ray data
measurements, and to affirm its validity, we compare the resonance modes of the approximated straight tube to the modes recorded from the lip-excited conch shell. Finally, we study wave propagation in conical and exponential spiral strings and tubes in more general cases, where numerical simulation is carried out whenever the theoretical solutions are hard to find. In the case of the strings, we also computed the resonance modes as well as the time dependent behaviour.