Interactive voice response apparatus capable of distinguishing between user's incoming voice and outgoing conditioned voice prompts

A method of detecting a user's spoken command to an interactive apparatus, said method comprising:

• outputting a signal representative of conditioned speech, wherein said signal representing conditioned speech has had a speech signal component removed therefrom, the removed signal component being present in users' spoken commands;
• monitoring an input signal to the interactive apparatus for the presence of said component;
• and
• detecting the presence of the user's spoken command in said input signal by detecting the presence of said removed signal component during issuance of the conditioned speech.

An interactive apparatus comprising:

• signal output means arranged in operation to output a signal representative of conditioned speech;
• signal input means arranged in operation to receive a signal representative of a user's spoken command;
• wherein the signal representing the conditioned speech has had a speech component removed therefrom, the removed component being present in the signal representing said spoken command;
• wherein the removed component is a frequency within one or more portions of the frequency spectrum between 80 Hz and 1500 Hz or a plurality of spaced short time segments;
• and
• command detection means operable to detect a user's command spoken during issuance of the conditioned speech by detecting the component removed from the signal representing the conditioned speech in an input provided to the signal input means.