• 喚よぶ — to call out; to summon
• 喚声かんせい — a shout; outcry (lit.)
• 喚起かんき — arousal; calling attention; galvanizing
• 叫喚きょうかん — cries and shouts
• 召喚しょうかん — summons; citation

With the mouth radical 口, 喚 is about strong voice: raising a call, shouting, summoning. Think of a voice that pulls people’s attention.