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An acoustic hailing device (AHD) is a specialized loudspeaker that emits high-power sound waves for communicating at a distance. AHDs vary in design, output, and usability. == Overview == Acoustic hailing devices are acoustic devices capable of outputting highly intelligible sound at very high volumes. The distance at which acoustic hailing can be effective varies based on several factors including the sound level, directionality, and frequency of the acoustic source, the sensitivity and directionality of the receiver, and the transmission channel environment. The sound level diminishes or attenuates with distance. Consequently, as a general rule, higher source levels have greater range. Acoustic hailing devices can come in two forms; # Directional models: These AHDs are characterized by their ability to create long-range, directional voice communications and warning tones. Their directionality is typically 5° to 60° radius conical at a 2 kHz tone. # Omnidirectional models: These acoustic hailing devices are capable of creating 360° voice communications and warning tones. These devices are capable of being heard over 1.5 miles away from the emitter head. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「acoustic hailing device」の詳細全文を読む スポンサード リンク
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