Final answer:
The most popular tool to measure internal communications effectiveness is the employee survey, which gathers feedback to improve communication strategies.
Step-by-step explanation:
The most popular tool used for measuring internal communications effectiveness is the employee survey. These surveys are designed to gather feedback from staff on a wide range of issues including their understanding of company goals, clarity of information received, and the effectiveness of various communication channels. Metrics derived from these surveys, such as engagement scores and open feedback, help organizations to identify areas for improvement and assess the impact of their internal communication strategies.