Chemical composition: Hearing insect defensive volatiles

Abstract

Highlights d The defensive secretion emitted by insects is often a mixture of volatiles d Volatiles were translated into sounds by sonification using parameter mapping d Chemical signals were repulsive for predators, as were the sounds for humans

Parameter Mapping Sonification of Human Olfactory Thresholds

“…In this context, sonification is a complementary or alternative way to obtain comparative, quantitative data. Its advantage is that bioassays are less necessary; such experiments using living organisms may be difficult to set up [12]. More generally, the sonification of medical measures, biological and seismological data, etc., sometimes allows a better interpretation of raw data than via their visual representation that may be less informative [14,20], but listening to such sonified data often requires a preliminary auditory training of the operator [13,14,21].…”

“…Reference [12] made three levels of arbitrary choices: (1) the assignment in Massive of a specific preset sound to each chemical class; (2) a general, preselected setting of the parameter mapping condition, on which most of the study relies, then randomizing the conditions to find those leading to higher correlation results; and (3) the mixing of molecule audio into a species audio, according to the relative chemical concentrations in the original insect secretion. Here, the first and third levels were not considered, the first one since the present sound was kept the same for all sonified molecules, and the third one because only single molecules were studied.…”

“…A batch record of all 100 molecules led to as many WAV files. Each audio file was analyzed with another application written in Processing to calculate the Lpeak values that were then averaged over the left and right audio channels [12,55]. Overall, at least 5000 audio files were generated during the study.…”

“…Volatiles acting as repellents, that is, at distance and through the olfactory sense [6], are often used by phytophagous insects against the attack of predators [1,[7][8][9]. As a first application of sonification [10,11] to chemical ecology, several insect species belonging to a group of phytophagous hymenopterans, the nematines, were studied [12]. From the chemical profile of the defensive volatile secretions of these insects, each single compound, or molecule, was subjected to sonification, by which chemical parameters were converted into sound parameters (Figure 1).…”

“…Testing correlations between Lpeak values and bioassay results revealed that both datasets are significantly positively correlated, which suggests that the audio clips contain information about the repellent bioactivity (Figure 1). Thus, practically speaking, testing audio on humans can be replaced by the more convenient process of measuring Lpeak values from the audio [12]. Any sonification process involves some subjectivity and arbitrary choices when assigning datasets to sound parameters.…”