ACTIVE NOISE CANCELLATION IN A DUCT WITH HIGHLY TURBULENT AIRFLOW

摘要

Test results indicate that for broad band noise reduction:1. turbulence control devices, such as honeycomb sections and perforated plates can be usedto significantly improve the coherence measured between the input and error microphonesresulting in noise reduction when using an ANC system in a duct with turbulent airflow.2. ANC is most effective for the attenuation of low frequency noise in ducts below approximately125 Hz. At these frequencies, ANC systems require less space at the application pointthan passive systems designed to attenuate in this frequency range.