Acoustic enhancement of frequencies with large amplitude variation in an active noise cancellation system

Abstract

An active noise attenuation system includes a speaker, and a microphone. The microphone detects a combination of sound from the speaker and noise in the system. The resulting noise is compared with a reference signal. The reference signal is a desired signal for the system. The combination of the reference signal and the desired signal results in a correction signal. The system of this invention includes first and second reference signal generation paths. A first path generates a signal according to a multiplier and a digital model the system. The second path generates an absolute sound pressure level according to engine rpm. The absolute sound pressure level provides a reference signal for shaping sound at orders of inconsistent or undetectable engine sound. The system selects or combines reference signals from each signal generation path to cover all engine sound orders

Dependencies are inferred from the claim text.