Singing‐sand avalanches without dunes

Abstract

Singing‐sand dunes have attracted curiosity for centuries and are now the subject of controversy. We address here two aspects of this controversy: first the possible link between the frequency heard and the shear rate (for a gravity avalanche on a dune slip‐face, scaling as 0.4g/d , with d the ‘mean’ grain diameter), and second, the assumed necessity of a layered dune structure under the avalanche that acts as a resonator. Field recordings of singing dunes over the world reveal that they can present very different spectral characteristics: a dune with polydisperse grains produces a very broad and noisy spectrum, while a dune with sorted grains produces a well‐defined frequency. Performing laboratory avalanches on a hard plate with singing‐dune sand shows that there is no need for a dune below the sand avalanche to produce the singing sound, anda fortiorineither for the dune's layered structure nor for its particular sound transmission. By sieving the polydisperse grains, the same well‐defined frequency is obtained to that of the dune with sorted grains, with the same diameter‐frequency relation. The various frequencies heard in the field avalanches match the shear rates not calculated from the average size, but from the various peaks of the grain size distributions.

Sound mechanics from squeaky and booming dune sands

“…The model can account for the modes of vibration but not for the low frequency content. However, not long after the publication of this study, Dagois-Bohy et al [6] and Dagois-Bohy et al [7] brought booming sand to their laboratory and demonstrated that an avalanche of about 2 cm in thickness on an inclined plane could produce the frequency spectra observed during a natural avalanche on a dune slip face. Furthermore, it is not evident that the theoretical models proposed by Andreotti [2] and Andreotti and Bonneau [8] could predict the observed frequency spectra and more so the low frequency content during a free avalanche on a dune slip face.…”

“…There is a faint evidence of such a low frequency content in Fig. 1 in Dagois-Bohy et al [7] at time equal to 6 and 17 s. There is no low frequency content in the reports by Hunt and Vriend [5] and by Vriend et al [23] but that could be due to geophone cut-off frequency at around 25 Hz.…”

“…According to Sholtz et al [18], the following authors, Poynting and Thomson [24]; Reynolds [25] argued that a shearing stress on a closed packed granular substance could result in one grain layer sliding over another grain layer and in the process create a periodic expansion-contraction of the substance. Then, Dagois-Bohy et al [7], argued that grain layers in an avalanching band oscillate sinusoidally and that results in a musical sound without the aid of a standing or traveling mode of vibration. However, the acceleration signal shown in the lower inset in Fig.…”

Linear and nonlinear wave propagation in booming sand dunes

“…5 Similar broadband sounds have also been recorded in the laboratory using a rotating bed moving past a fixed paddle. 11,12 Douady et al 11 and Dagois-Bohy, Courrech du Pont, and Douady 9 observed that the frequency of burping sounds depends on the shear rate and the particle diameter of the sample.…”

Acoustic methods in physical geography: Applications and future development

“…Such sounds were noted by Charles Darwin from his time in Chile in 1835 (see the review of booming sand dunes by Hunt and Vriend 2010). Darwin speculated that the sound was the result of sand avalanching (Dagois-Bohy et al, 2012). Criswell et al (1975) presented the first analysis of the sounds generated by experimenters deliberately disturbing dune flanks.…”