Often reworded as "What you do speaks so loudly that I cannot hear what you say," and other variants. Famously quoted by John F. Kennedy in 1960 as "What we are speaks louder than what we say." Most variants are attributed to Emerson, who himself may have been streamlining an oft repeated sentiment.
The author is a Canadian man who wrote the quote on a greeting card for Carleton Cards in the mid 1970's . In return for his quote he was remunerated and signed away the copyright to Carleton Cards http://wiki.answers.com