LAUSR

The female Anopheles gambiae s.s transmits malaria to human beings through bites. Malaria has been reported to be responsible for severe morbidity and mortality in Africa and the world causing substantial costs to both individuals and governments. Notwithstanding the many efforts directed towards the control of malaria, the rate at which the malaria cases and deaths are declining is yet to reach satisfactory levels hence the need for multipronged approaches in vector control. Recent studies on the startle response of the African female A. gambiae to animal sounds showed a 46% evasive response elicited by the 35-60 kHz recorded sound of O. tormota. This being an indicator of the feasibility of using sounds in mosquito control, there was need to analyse the acoustic propagation parameters of the natural sounds of Delphinapterus leucas and Odorrana tormota which are fundamental in the startle of the female Anopheles gambiae. This study determined and analysed the acoustic propagation parameters of the sounds of D. leucas and compared with the acoustic propagation parameters of the sound of O. tormota. The sound of the Beluga Whale D. leucas was recorded by Wavshark system, C75 and the C55 hydrophone at a sampling frequency of 128 kHz while swimming in the tank of the Vanaqua. The sound of O. tormota was recorded by 702 digital recorder from the Huangshan Hot Springs, Anhui Province in China at a sampling frequency of 192 kHz. The Avisoft-SAS LAB Pro, Batsound and Raven Pro 1.5 software were used in conversion of sampling frequencies to 192kHz, appending sound clips, mixing sound clips and for data analysis. Fourier transform was performed on the spectrum of the sound of D. leucas and the new sound samples of O. tormota to determine the acoustic propagation parameters through automatic parameter measurements. Spectral analysis of the sound of D. leucas and O. tormota showed presence of harmonics stretching to ultrasonic levels, frequency modulation (FM) and constant frequency (CF) modulation components in both. The mean of the fundamental frequency (mean entire) of D. leucas was 1.684kHz, less by 3.712kHz from that of the new sound samples of O. tormota. There existed no significant difference between the fundamental frequencies of the sound of D. leucas and the sound of O. tormota at p = 0 .846 > 0.05 determined at 95% confidence interval. The sound of D. leucas recorded a maximum value of 64.800kHz which was 25.500kHz above the maximum frequency (mean) of the sound of O. tormota, the difference which was highly significant (p = 2.8975 x 10 < 0.05). The sound of D. leucas which was characterised by 64.10kHz bandwidth (mean entire) wider than that of O. tormota by 53.64kHz, a difference which was highly significant (p = 1.1225 x 10 < 0.05). Also the peak amplitude (mean entire) for the sound of D. leucas was 89.05Pa less by 39.837kHz from that of the sound of O. tormota differing significantly (p = 4.88x10 < 0.05). The signal energy of D. leucas did not differ significantly (p = 0.9857 > 0.05) from the energy possessed by O. tormota. The mean acoustic energy of D. leucas was 0.07Pas whereas the O. tormota possessed 2,496.63Pas. The pulsate signal power of the sound of D. leucas fluctuated between 36 dB and 56 dB less compared to the power in O. tormota that fluctuated between 43 dB and 89 dB. These results provide critical parameter essential in the study of mosquito repellence and design of a repellent device.