auditor

noun
1
a person who officially examines the business and financial records of a company
حسابرس, بازرس حساب
2
a person who attends a college course, but without having to take exams and without receiving credit
مستمع آزاد
3
a person who listens
شنونده, گوش‌دهنده, مستمع
His auditors had to listen carefully to understand what he was saying.