The phrase “effectiveness of communication in the workplace” you rendered in your query can mean different things. So, you could start by clearly conceptualizing the construct(s) of interest. In the meantime, you might find the following articles helpful.

Jena, L. K., & Pradhan, S. (2020). Workplace persuasion: Conceptual model, development and validation. Global Business Review, 21(2), 567–585. https://doi.org/10.1177/0972150918761086

Rubin, R. B., & Martin, M. M. (2009). Development of a measure of interpersonal communication competence. Communication Research Reports. https://doi.org/10.1080/08824099409359938

ter Hoeven, C. L., & van Zoonen, W. (2020). Helping others and feeling engaged in the context of workplace flexibility: The importance of communication control. International Journal of Business Communication, 2329488419898799. https://doi.org/10.1177/2329488419898799

Good luck,

The effectiveness of communication requires an exploratory approach.An open ended interview can be helpful to better understand communication.

You can develop one using exploratory sequential mixed methods research design.