Sound any bus horn by the Checkpoint

How do you complete "Sound any bus horn by the Checkpoint"?

This is step 3 of 3 in Clamoring for Attention, given by Shani. It is completed on The Blue Gate.

• Clamoring for Attention
• The Blue Gate

What are the other objectives in Clamoring for Attention?

Clamoring for Attention has 3 objectives in total: Use 3 Wires to repair and sound the emergency siren by the Warehouse Complex, Use a Battery to start the boom box in the Village and Sound any bus horn by the Checkpoint.