Active attenuation system with on-line modeling of feedback path

• US 5,621,803 A
• Filed: 01/25/1996
• Issued: 04/15/1997
• Est. Priority Date: 09/02/1994
• Status: Expired due to Term

• Current Assignee: Digisonix Incorporated
• Original Assignee: Digisonix Incorporated
• Inventors: Laak, Trevor A.
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): LEE, PING
• Application Number:
  US08/591,126
• Time in Patent Office: 446 Days
• Field of Search: 381/71, 381/94
• US Class Current: 381/71.11
• CPC Class Codes: G10K 11/17817 between the output signals and the error signals, i.e. secondary path
• CPC Class Codes: G10K 11/17819 between the output signals and the reference signals, e.g. to prevent howling
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17879 using both a reference signal and an error signal
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 2210/112 Ducts
• CPC Class Codes: G10K 2210/3012 Algorithms
• CPC Class Codes: G10K 2210/3017 Copy, i.e. whereby an estimated transfer function in one functional block is copied to another block
• CPC Class Codes: G10K 2210/30232 Transfer functions, e.g. impulse response
• CPC Class Codes: G10K 2210/3027 Feedforward
• CPC Class Codes: G10K 2210/3049 Random noise used, e.g. in model identification
• CPC Class Codes: G10K 2210/3053 Speeding up computation or convergence, or decreasing the computational load

Abstract

In an active adaptive attenuation system having a main model, a second adaptive filter model is provided having an input from the output of the main model, and an output supplied to the input of the main model. A copy of the main model has an input from the input to the second model and an output supplied to a multiplier multiplying the error signal and the output of the copy and supplying the resultant product as a weight update signal to the second model.

Claims

1. An active adaptive attenuation system having an output transducer outputting a control signal combining with a system input signal to yield a system output signal, an error transducer sensing said system output signal and outputting an error signal, a first adaptive filter model having a model input from a reference signal correlated to said system input signal, an error input from said error signal, and a model output outputting a correction signal to said output transducer to introduce said control signal to minimize said error input, a second adaptive filter model having a model input from said correction signal, an error input from said error signal, and a model output also supplied to said model input of said first model, wherein each model actively adapts during active adaptive on-line operation of the other model, a third adaptive filter model having a model input and having a model output summed with said error signal and modeling the transfer function from the output of said first adaptive filter model to said error transducer, an auxiliary signal source supplying an auxiliary signal to said output transducer and to the model inputs of each of said second and third models, such that said auxiliary signal is filtered by said second adaptive filter model and supplied to the model input of said first model.

2. The invention according to claim 1 comprising a series connection of a copy of said first adaptive filter model and a copy of said third adaptive filter model, said series connection having an input from the output of said first adaptive filter model and also from said auxiliary signal source, said series connection having an output supplied to a multiplier multiplying said error signal and the output of said series connection and supplying the resultant product as a weight update signal to said second adaptive filter model.

3. The system according to claim 1 comprising a summer summing the output of said first adaptive filter model and said auxiliary signal from said auxiliary signal source and supplying the resultant sum to said output transducer and to the input of said second adaptive filter model.