A method (200) for controlling audio signals to an FM transmitter and a loudspeaker of a hands-free adapter first sends a first audio signal to the loudspeaker (242) and measures and records a loudspeaker audible artifact such as echo return loss (244) and/or echo tail length (246). Next, the hands-free adapter sends a second audio signal to the FM transmitter and the loudspeaker (252) and measures and records an FM transmitter and loudspeaker audible artifact such as echo return loss (254) and/or echo tail length (256). If the FM transmitter and loudspeaker audible artifact minus the loudspeaker audible artifact is greater than a threshold (263, 266), the hands-free adapter sends a third audio signal to the FM transmitter only (270), and if the FM transmitter and loudspeaker audible artifact minus the loudspeaker audible artifact is not greater than the threshold, the hands-free adapter sends the third audio signal to both the FM transmitter and the loudspeaker (280).