Highly Uncomfortable Mosquito Signal Based on Subjective Evaluation

In recent years, the mosquito signal has been increasinegly used as a method of dispersing noisy groups of young people from public spaces. The mosquito signal is a high-frequency signal—around 17 kHz—that is audible to young people but not to older adults. A recent study on an acoustic system using the mosquito signal indicated that it was able to disperse young people gathered at a park in Japan in around three minutes, which clearly shows that the mosquito signal is both effective and useful. In our study, we have attempted to design a highly uncomfortable mosquito signal for the dispersal of human noise sources. We focused on three kinds of signals: sine signals, environmental signals, and signals based on the auditory sense. First, we designed the sine signals. We used a highly pure sine wave because conventional reports have suggested that highly uncomfortable signals tend to hold a sharper attenuation from the main peak in frequency. Next, we designed the environmental signals. We used a combination of three different signals: a motor noise to simulate a cleaner, a crying noise to simulate an infant, and a scrub noise to simulate foamed styrol. We then convoluted a high-pass filter to these signals. Finally, we designed the signals based on the auditory sense. We used the same three signals asine the previous design but shifted from a lower frequency (1–5 kHz) to a higher frequency band, because humans tend to mainly hear the signal transmitted on 1–5 kHz. We used the mean opinion score (MOS) to conduct a subjective evaluation. Results demonstrated that the new mosquito signals were more uncomfortable than the conventional ones, and that the pure sine mosquito signal at 15 kHz was the most uncomfortable of the proposed signal sine future work, we intend to design an even more uncomfortable mosquito signal based on complex sine waves. We will also focus on controlling the signal’s output area to reduce the negative effects on local citizens and animals.