# Acoustic Classification of Singing Insects Based on MFCC/LFCC Fusion
## 1 Introduction  
Insects, with more than one million described species, form the largest ecological group on Earth, and there may be as many more yet to be identified. In the species acoustic classification field, considerable studies have been made to create intelligent and automatic systems to correctly identify and classify these species. This field is mostly based on the ability of these species to create a specific sound either deliberately or by its biological activities as moving from one place to another, as a defense against predators or any other goal as described in many studies as in [1; 2; 3; 4]. Research on those sounds has revealed that it is possible to obtain reliable information of a taxonomic classification and this could be used to measure the biodiversity of a habitat as presented in [5]. The development of tools to have knowledge of the biodiversity will give more information and indicators about the state of the biodiversity [6]. In particular, insects play an important role in ecological balance and biodiversity conservation [4; 7]. This research has proven to be of great interest to many fields due to the importance of the identification and classification of insects' sounds. Insects are beneficial organisms in agriculture and forestry activities. Nevertheless, in some cases, commercial crop growers consider these species as pests, and these insects are eliminated by insecticides. Moreover, the tasks of detection and identification of species are performed by biologists, and this human expertise is expensive in terms of time and money. Hence, an intelligent system as the one presented in this work could help to reduce these costs and time in identification tasks. Insects exhibit a wide variety of sound generation mechanisms [2; 8; 9; 10]. Typically, katydids and crickets (Orthoptera order) produce sounds by stridulation rubbing a scraper or plectrum against a file. The stridulation organs are located on their forewings, the file is composed of a row of teeth which is dragged over a callous area (the scraper) generating a vibration. The resulting sound signal is then amplified by resonance on the harp and the mirror structures producing species-specific frequency and temporal patterns. This mechanism is driven by descending commands from the brain to the thoracic central pattern generator (CPG). A deeply neurophysiological study of this acoustic behavior can be found in [11]. On the other hand, cicadas (Hemiptera order) mainly make sounds using a pair of tymbal organs situated on the sides of their abdomen. Each tymbal is composed of a ribbed membrane attached to a tymbal muscle. A series of rapid muscle contractions deform the membrane making it vibrate, producing the sound. The signals produced by insects are distributed over a wide frequency range between 15 Hz and 100 KHz, where the carrier frequency is influenced by the size of its sound production organs [12], but these are not always correlated with the insect body size [13]. Crickets usually produce almost pure tone sinusoidal signals with carrier frequencies around 2-10 KHz. By contrast, katydids normally generate broadband signals up to 100 KHz. Songs vary widely across cicada species and include wide band and almost pure sinusoidal sound signals. The aim of this research is to create a bioinformatic expert system based on digital acoustic signal processing and machine learning techniques to classify species of crickets, katydids and cicadas. Thus, the contribution of this paper is the introduction of a methodology based on a new sound parametrization technique to obtain a more robust representation of the chants of the insects. This methodology allows a more effective representation of insect sounds fusing two types of cepstral coefficients, MFCC and LFCC, to gather information across the whole spectrum. Moreover, this approach can be implemented in a real system to perform the task of detection, segmentation, parameterization and classification of these sounds without human intervention.