Possible Clues:

• Codeword, cautionary signal, sent around Switzerland, place where voices resound
• Room with resounding walls
• Sheep's environment?
• Place for hollow sound effects
• Note chocolate orange with hard centre that may repeat on you
• Ringing? Check warning light in part of recording studio
• *Situation promoting confirmation bias
• Environment where beliefs go unchallenged
• Environment that reinforces one's biases
• Where tests are made to ensure sound quality