A decrease in the watermark detection rate is a fatal problem in employing audio watermarks for applications in which a watermarked signal is transmitted through the air. The enforcement of watermarks using an error-correcting code is a solution to this problem. Low-density Parity Check (LDPC) coding is a recent error-correcting code; it shows good performance close to Shannon?s limit. Therefore, in the present study, watermark detection rates when the watermarks were coded combined with and without LDPC coding were evaluated through computer simulations and experiments in a real room. The results showed that employing LDPC coding raised the watermark detection rate by around 15 percentage points for an additive white Gaussian noise and by around 20 points from around 60% to around 80% in an actual reverberation environment.