Spectral wells for inserting watermarks in audio signals

A machine or group of machines for watermarking audio, comprising:

• an input that receives an audio signal and a watermark signal,
• the audio signal including at least one of:
• a first spectral portion corresponding to a first frequency range, a second spectral portion corresponding to a second frequency range of higher frequency than the first frequency range, and a third spectral portion corresponding to a third frequency range of higher frequency than the second frequency range, or
• a first temporal portion corresponding to a first time range, a second temporal portion corresponding to a second time range of later time than the first time range, and a third temporal portion corresponding to a third time range of later time than the second time range,
• the watermark signal including multiple symbols;
• and
• an encoder circuit including a controller configured to:
• measure amplitude of at least one of:
• the first spectral portion and the third spectral portion, or
• the first temporal portion and the third temporal portion;
• and
• amplify or attenuate amplitude of a first symbol, from the multiple symbols, such that amplitude of the first symbol is based on the amplitude of the at least one of:
• the first spectral portion and the third spectral portion, or
• the first temporal portion and the third temporal portion;
• the encoder circuit configured to insert the first symbol, from the multiple symbols, in a spectral well, the spectral well corresponding to at least one of:
• the second spectral portion and a temporal portion when the amplitude of the first spectral portion and the amplitude of the third spectral portion exceed the amplitude of the second spectral portion, and
• the second temporal portion and a spectral portion when the amplitude of the first temporal portion and the amplitude of the third temporal portion exceed the amplitude of the second temporal portion.