1. 1) Ministry of Land, Infrastructure and Transport, Japanese Road Traffic Law, Chap. 3, sec. 10, art. 54.
2. 2) Ministry of Land, Infrastructure and Transport, Safety Standard for Road Transportation Vehicles, Chap. 2, art. 43.
3. 3) T. Hashimoto, ``On the sound quality of vehicle warning signals,'' J. INCE/J, 26, 20-24 (2002) (in Japanese).
4. 4) K. Nagahata, ``Forecasting the future soundscape by reviewing the history of noise problems: A study on the history of the noise problems caused by loudspeakers and horns of vehicles,'' J. INCE/J, 30, 344-351 (2006) (in Japanese).
5. 5) M. Okahara, ``Jidoshayo-keionki no onryosokutei (Measurements of the sound levels of the vehicle horns),'' J. Acoust. Soc. Jpn. (J), 6, 80-84 (1950) (in Japanese).