Patent ID: 8848901

Claim:
A noise reduction system comprising: a telephone controller configured to connect a plurality of telephones having microphones, including a first, a second and a third telephone, to a public telephone network, the telephone controller including a processor and a plurality of inputs, including first, second and third inputs, for receiving, respectively, a first microphone signal from the first telephone, a second microphone signal from the second telephone and a third microphone signal from the third telephone, wherein the first microphone signal reflects sound received at the first telephone's microphone, wherein said sound received at the first telephone's microphone includes sound from a user of the first telephone, sound from a user of the second telephone, and sound from a user of the third telephone; a processor connected to said plurality of inputs; and a computer-readable medium encoded with a program to control said processor, wherein the program causes said processor to control a first adaptive noise cancellation process to receive as input, the first and second microphone signals and, based on the first and second microphone signals, remove from the first microphone signal at least a portion of the sound received at the first telephone's microphone from the user of the second telephone, and output a corresponding first filtered first microphone signal; and to control a second adaptive noise cancellation process to receive as input, the first filtered first microphone signal and the third microphone signal and, based on the first filtered first microphone signal and the third microphone signal, remove from the first filtered first microphone signal at least a portion of the sound received at the first telephone's microphone from the user of the third telephone, and output a corresponding second filtered first microphone signal, wherein the first adaptive noise cancellation process includes generating a modified second microphone signal modeling the sound of the user of the second telephone as received at the microphone of the first telephone, and combining the modified second microphone signal with the first microphone signal to generate the first filtered first microphone signal, and wherein the second adaptive noise cancellation process includes generating a modified third microphone signal modeling the sound of the user of the third telephone as received at the microphone of the first telephone, and combining the modified third microphone signal with the first filtered first microphone signal to generate the second filtered first microphone signal.