Active noise control system

• US 20040240677A1
• Filed: 05/27/2004
• Published: 12/02/2004
• Est. Priority Date: 05/29/2003
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Takahashi, Akira, Inoue, Toshio, Nakamura, Yoshio, Onishi, Masahide
• Granted Patent: US 7,340,064 B2
• Time in Patent Office: Days
• US Class Current: 381/71.4
• CPC Class Codes: G10K 11/17825 Error signals
• CPC Class Codes: G10K 11/17833 by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels
• 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 11/17883 the reference signal being derived from a machine operating condition, e.g. engine RPM or vehicle speed
• CPC Class Codes: G10K 2210/128 Vehicles
• CPC Class Codes: G10K 2210/3016 Control strategies, e.g. energy minimization or intensity measurements
• CPC Class Codes: G10K 2210/30391 Resetting of the filter parameters or changing the algorithm according to prevailing conditions

Abstract

An active noise control system is provided which cancels a noise using a secondary noise from a speaker that is operated in accordance with an output from an adaptive controller. The system is configured such that microphone monitor interrupts a switch to thereby stop the secondary noise from being produced, when an error signal delivered by a microphone used for an adaptive computation in an LMS processing portion has the same sign for a predetermined duration. This allows the system to prevent the user from hearing an abnormal acoustic noise resulting from an abnormal operation or divergence of an adaptive filter even when the output signal from the microphone used for the adaptive computation is indicative of an abnormal level.

Claims

1. An active noise control system comprising:

an adaptive controller for computing an amplitude and a phase of a secondary noise which actively cancels a primary noise generated in a passenger compartment;

secondary noise generator for producing said secondary noise in the passenger compartment;

a microphone for sensing a residual noise resulting from the interference of said secondary noise with said primary noise; and

microphone monitor for stopping said secondary noise being produced from said adaptive controller when output signals delivered by said microphone to be supplied to said adaptive controller have the same positive or negative sign for a predetermined duration.

2. An active noise control system comprising:

an adaptive controller for computing an amplitude and a phase of a secondary noise which actively cancels a primary noise generated in a passenger compartment;

secondary noise generator for producing said secondary noise in the passenger compartment;

a microphone for sensing a residual noise resulting from the interference of said secondary noise with said primary noise; and

microphone monitor for stopping said secondary noise being produced from said adaptive controller when a ratio between a duration of the positive sign of output signals delivered by said microphone to be supplied to said adaptive controller and that of the negative sign thereof is greater than or equal to a predetermined value.