05319735 is referenced by 599 patents and cites 12 patents.

A code signal representing a sequence of code symbols carrying digital information is generated with the frequency components of the code signal being essentially confined to a preselected signalling band lying within the bandwidth of an audio signal within which the code signal is to be embedded. The audio signal is continuously frequency analyzed over a frequency band encompassing the signalling band and the code signal is dynamically filtered as a function of the analysis thereby to provide a modified code signal with frequency components which are, at each time instant, essentially a preselected small proportion of the levels of the corresponding audio signal frequency components. Accordingly, the modified code signal can be combined with the audio signal to obtain a composite audio signal which is not readily distinguishable from the original audio signal by listening. Furthermore, the digital information can be recovered from the composite audio signal by a procedure which is essentially the compliment of that used to obtain the composite audio signal.

Title
Embedded signalling
Application Number
7/808913
Publication Number
5319735
Application Date
December 17, 1991
Publication Date
June 7, 1994
Inventor
Alan G Derr
Westford
MA, US
Patrick M Peterson
Cambridge
MA, US
Marcos A Bergamo
Wellesley
MA, US
Herbert Gish
Newton
MA, US
A W F Huggins
Arlington
MA, US
Salim E Roukos
Scarsdale
NY, US
Robert D Preuss
Boston
MA, US
Agent
Henry D Pahl Jr
Assignee
Bolt Beranek and Newman
MA, US
IPC
G10L 3/00
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