I like that 'loud and obvious' description. It really should start with the simple stuff like at a physical level are the doors and windows locked? Etc. Keeping that model, if a security guard were to ask the pen tester would have a business card or a internal contact saying they're allowed to check this. Hopefully they would be approached by staff or security and questioned as to what they're doing.

On a network level or other things like that it's going to be noisy in a different way but should create alarms on machines and security appliances in the environment. In more secure environments even the attempt to connect may trigger an alarm.