Abstract: Methods and systems for encoding and decoding data in an audio channel are provided. At least one notch attribute for each of a set of notches to be applied to a source audio channel corresponding to data to be encoded is determined. The data is encoded by applying notch-filtering to the source audio channel to create a modified audio channel having the set of notches having the at least one notch attribute. The notches in the modified audio channel are then analyzed to determine at least one characteristic of each of the notches, and data is then decoded from the at least one characteristic of each of the notches.

Abstract: A method and system for encoding data in audio are provided. A sequence of time deltas is generated at least partially based on a set of data. At least some of the time deltas are less than a threshold at which a human naturally detects an echo. A second audio channel is generated from a first audio channel, the second audio channel being temporally shifted relative to the first audio channel using the sequence of time deltas. The first and second audio channels are played back simultaneously via at least one audio transducer. The composite audio channel is registered via at least one microphone and processed to identify the first and second audio channels that are at least partially relatively temporally shifted. A sequence of time deltas by which the second audio channel is shifted temporally relative to the first audio channel is determined, and a set of data is decoded at least partially therefrom.

Abstract: A method and system for encoding data in audio are provided. A sequence of time deltas is generated at least partially based on a set of data. At least some of the time deltas are less than a threshold at which a human naturally detects an echo. A second audio channel is generated from a first audio channel, the second audio channel being temporally shifted relative to the first audio channel using the sequence of time deltas. The first and second audio channels are played back simultaneously via at least one audio transducer. The composite audio channel is registered via at least one microphone and processed to identify the first and second audio channels that are at least partially relatively temporally shifted. A sequence of time deltas by which the second audio channel is shifted temporally relative to the first audio channel is determined, and a set of data is decoded at least partially therefrom.

Abstract: A polyphase digital filterbank extracts a spectral envelope composed of thirty-two bands, having uniform bandwidths, from a speech signal. The spectral envelope is then compressed into a predetermined number of bands having uniform bandwidths. Spectral energy features are extracted from the compressed envelope and are utilized to form templates representing the speech signal.

Abstract: An intercommunication system makes use of existing quad wiring to provide intercom communication between the subsets of the system, as well as communication with a standard central office, or an "outside line". Each subset is provided with a control sequencer for selectively connecting the set to either an "intercom" or an "outside" or C.O. line. When the handset of a subset is lifted off the respective hookswitch, the subset is automatically connected to intercom line and signalling between subsets can occur with the outside line on "hold". The hold is released automatically when another handset is picked up.Two indicators show activity on the two lines respectively.