Attracting insects with an acoustic laser

Abstract

It has been demonstrated that female Mediterranean fruit flies (Ceratitis capitata) are attracted to a trap by a pure tone at approximately the spectral peak (330 Hz) of the males mating call [Mankin et al., J. Econ. Entomol. 97, 1299–1309 (2004)]. Recent research [Sueur et al., ‘‘Sound radiation around a flying fly,’’ J. Acoust. Soc. Am. 118, 530–538 (2005)] suggests that a more complex tone that combines an amplitude-modulated fundamental and a second-harmonic component could produce more effective acoustic bait. We will describe a thermoacoustic sound source [S. L. Garrett and R-L. Chen, Echoes 10, 4–5 (2000)] that combines two closely tuned quarter-wavelength resonators designed to produce a beating fundamental of adjustable modulation depth. A third source produces the second harmonic. The trio of sources generates the desired signal at levels of 90 to 100 dB 1 meter from the array. Since the sound is produced from electrically heated filaments, no oscillators, amplifiers, or electro-acoustic transducers are required. When the pair of fundamental resonators are placed side-by-side, the beating occurs uniformly in space. When placed back-to-back, the dipolar radiation pattern rotates to produce the beating in time at any fixed location. We hope to have results with insect subjects by the time of the meeting. [Work supported by an endowment from United Technologies Corporation.]