Apparatus for and methods of including codes into audio signals and decoding such codes

Apparatus and methods for including a code (68) having at least one code frequency component in an audio signal (60) are provided. The abilities of various frequency components in the audio signal to mask the code frequency component to human hearing are evaluated (64), and based on these evaluations an amplitude (76) is assigned to the code frequency component. Methods and apparatus for detecting a code in an encoded audio signal are also provided. A code frequency component in the encoded audio signal is detected based on an expected code amplitude or on a noise amplitude within a range of audio frequencies including the frequency of the code component.