Apparatus and methods for including codes in audio signals and decoding

A method for including a code having at least one code frequency component with an audio signal having a plurality of audio signal frequency components, comprising the steps of:

• evaluating an ability of a first set of the plurality of audio signal frequency components to mask the at least one code frequency component to human hearing to produce a first masking evaluation;
• evaluating an ability of a second set of the plurality of audio signal frequency components to mask the at least one code frequency component to human hearing to produce a second masking evaluation;
• assigning an amplitude to the at least one code frequency component based on a selected one of the first and second masking evaluations;
• and
• including the at least one code frequency component with the audio signal.

An apparatus for including a code having a plurality of code frequency components with an audio signal having a plurality of audio signal frequency components, the plurality of code frequency components including a first code frequency component having a first frequency and a second code frequency component having a second frequency different from the first frequency, comprising:

• first masking evaluation means for evaluating an ability of at least one of the plurality of audio signal frequency components to mask a code frequency component having the first frequency to human hearing to produce a first respective masking evaluation;
• second masking evaluation means for evaluating an ability of at least one of the plurality of audio signal frequency components to mask a code frequency component having the second frequency to human hearing to produce a second respective masking evaluation;
• amplitude assigning means for assigning a respective amplitude to the first code frequency component based on the first respective masking evaluation and for assigning a respective amplitude to the second code frequency component based on the second respective masking evaluation;
• and
• code inclusion means for including the plurality of code frequency components with the audio signal.

An apparatus for including a code having a plurality of code frequency components with an audio signal having a plurality of audio signal frequency components, the plurality of code frequency components including a first code frequency component having a first frequency and a second code frequency component having a second code frequency different from the first frequency, comprising:

• a digital computer having an input for receiving the audio signal, the digital computer being programmed to evaluate an ability of at least one of the plurality of audio signal frequency components to mask a code frequency component having the first frequency to human hearing to produce a first respective masking evaluation and to evaluate an ability of at least one of the plurality of audio signal frequency components to mask a code frequency component having the second frequency to human hearing to produce a second respective masking evaluation;
• the digital computer being further programmed to assign a corresponding amplitude to the first code frequency component based on the first respective masking evaluation and to assign a corresponding amplitude to the second code frequency component based on the second respective masking evaluation;
• and
• means for including the plurality of code frequency components with the audio signal.

An apparatus for including a code having at least one code frequency component with an audio signal having a plurality of audio signal frequency components, comprising:

• tonal signal producing means for producing a first tonal signal representing a first substantially single one of the plurality of audio signal frequency components and a second tonal signal representing a second substantially single one of the plurality of audio signal frequency components different from the first substantially single one thereof,
• masking evaluation means for evaluating an ability of the first substantially single one of the plurality of audio signal frequency components to mask the at least one code frequency component to human hearing based on the first tonal signal to produce a first masking evaluation, and for evaluating an ability of the second substantially single one of the plurality of audio signal frequency components to mask the at least one code frequency component to human hearing based on the second tonal signal to produce a second masking evaluation,
• amplitude assigning means for assigning an amplitude to the at least one code frequency component based on a selected one of the first and second masking evaluations;
• and
• code inclusion means for including the at least one code frequency component with the audio signal.

A method for including a code having at least one code frequency component with an audio signal having a plurality of audio signal frequency components, comprising the steps of:

• producing a first tonal signal representing a first substantially single one of the plurality of audio signal frequency components and a second tonal signal representing a second substantially single one of the plurality of audio signal frequency components different from the first substantially single one thereof;
• evaluating an ability of the first substantially single one of the plurality of audio signal frequency components to mask the at least one code frequency component to human hearing based on the first tonal signal to produce a first masking evaluation;
• evaluating an ability of the second substantially single one of the plurality of audio signal frequency components to mask the at least one code frequency component to human hearing based on the second tonal signal to produce a second masking evaluation;
• assigning an amplitude to the at least one code frequency component based on a selected one of the first and second masking evaluations;
• and
• including the at least one code frequency component with the audio signal.

A programmed digital computer for detecting a code in an encoded audio signal, the encoded audio signal including a plurality of audio frequency signal components and at least one code frequency component having an amplitude and an audio frequency selected for masking the code frequency component to human hearing by at least one of the plurality of audio frequency signal components, comprising:

• an input for receiving the encoded audio signal;
• a processor programmed to establish an expected code amplitude of the at least one code frequency component based on the encoded audio signal, to detect the code frequency component in the encoded audio signal based on the expected code amplitude and to produce a detected code output signal based on the detected code frequency component;
• and
• an output coupled with the processor for providing the detected code output signal.

An apparatus for detecting a code in an encoded audio signal, the encoded audio signal having a plurality of frequency components including a plurality of audio frequency signal components and at least one code frequency component having a predetermined audio frequency and a predetermined amplitude for distinguishing the at least one code frequency component from the plurality of audio frequency signal components, comprising:

• means for determining an amplitude of frequency components of the encoded audio signal within a first range of audio frequencies including the predetermined audio frequency of the at least one code frequency component;
• means for establishing a noise amplitude for the first range of audio frequencies;
• and
• means for detecting the presence of the at least one code frequency component in the first range of audio frequencies based on the established noise amplitude thereof and the determined amplitude of frequency components therein.

A method for detecting a code in an encoded audio signal, the encoded audio signal having a plurality of frequency components including a plurality of audio frequency signal components and at least one code frequency component having a predetermined audio frequency and a predetermined amplitude for distinguishing the at least one code frequency component from the plurality of audio frequency signal components, comprising the steps of:

• determining an amplitude of a frequency component of the encoded audio signal within a first range of audio frequencies including the predetermined audio frequency of the at least one code frequency component;
• establishing a noise amplitude for the first range of audio frequencies;
• and
• detecting the presence of the at least one code frequency component in the first range of audio frequencies based on the established noise amplitude thereof and the determined amplitude of the frequency component therein.

A digital computer for detecting a code in an encoded audio signal, the encoded audio signal having a plurality of frequency components including a plurality of audio frequency signal components and at least one code frequency component having a predetermined audio frequency and a predetermined amplitude for distinguishing the at least one code frequency component from the plurality of audio frequency signal components, comprising:

• an input for receiving the encoded audio signal;
• a processor coupled with the input to receive the encoded audio signal and programmed to determine an amplitude of a frequency component of the encoded audio signal within a first range of audio frequencies including the predetermined audio frequency of the at least one code frequency component;
• the processor being further programmed to establish a noise amplitude for the first range of audio frequencies and to detect the presence of the at least one code frequency component in the first range of audio frequencies based on the established noise amplitude thereof and the determined amplitude of the frequency component therein;
• the processor being operative to produce a code output signal based on the detected presence of the at least one code frequency component;
• and an output terminal coupled with the processor to provide the code signal thereat.