A theoretical study of special acoustic effects caused by the staircase of the El Castillo pyramid at the Maya ruins of Chichen-Itza in Mexico

Abstract

It is known that a handclap in front of the stairs of the great pyramid of Chichen Itza produces a chirp echo which sounds more or less like the sound of a Quetzal bird. The present work describes precise diffraction simulations and attempts to answer the critical question what physical effects cause the formation of the chirp echo. Comparison is made with experimental results obtained from David Lubman. Numerical simulations show that the echo shows a strong dependence on the kind of incident sound. Simulations are performed for a (delta function like) pulse and also for a real handclap. The effect of reflections on the ground in front of the pyramid is also discussed. The present work also explains why an observer seated on the lowest step of the pyramid hears the sound of raindrops falling in a water filled bucket instead of footstep sounds when people, situated higher up the pyramid, climb the stairs.

Acoustic diffraction effects at the Hellenistic amphitheater of Epidaurus: Seat rows responsible for the marvelous acoustics

“…15 An expansion of the theory to pulsed spherical acoustic waves revealed special acoustic effects at Chichen Itza in Mexico. 7,8 The advantage of the theory is its ability to make quantitative simulations as they appear in reality. From those simulations, it is then possible to detect and characterize patterns and characteristics of the diffracted sound field such as in the case of a short sound pulse incident on the staircase of the El Castillo pyramid in Chichen Itza.…”

“…[4][5][6][7][8][9] The theory of diffraction of sound is based on the concepts of the Rayleigh decomposition of the reflected and transmitted sound fields. [10][11][12] The theory, earlier applied to describe a number of diffraction effects for normal incident ultrasound on corrugated surfaces, 13 has been used successfully to understand the generation of ultrasonic surface waves in the framework of nondestructive testing.…”

The Sunlight Effect of the Kukulcán Pyramid or The History of a Line

“…In Chichén-Itzá, for instance, standing on the great plaza, around 30 m. away from the center of the pyramid's north stairway, two Quetzal chirps followed by an echo can clearly be heard when you clap your hands once (the Quetzal is the famous long-tailed bird typical of Yucatán). Specialists in acoustics have investigated this effect and believe that the Quetzal's echo could be a sort of incident sound [Declercq et al 2004]. Another beguiling effect can be experienced when you stand midway in the Juego de Pelota, between its two immense walls, while another person at the end of the field can hear the words you whisper.…”

The Accuracy of Predicted Acoustical Parameters in Ancient Open-Air Theatres: A Case Study in Syracusae

“…In CATT-Acoustic, the diffraction after 1st order option was deactivated, even though it is usually suggested for ancient theatres [42], in order to take into account the current large amount of damage to the cavea steps in SR. In this way, it was possible to avoid the typical "chirp" echo due to diffraction phenomenon which has been attested to come from the regular stone steps in ancient theatres in empty conditions [43]. This phenomenon was not encountered during in situ measurements or recordings in SR.…”