MONO-SOURCE ACTIVE ABSORBOR IN A DUCT

It is proposed here that one kind of mono-source absorbor based on cancelling method and the structure of acoustic travelling wave probe.The probe can perform the functions both signal detecting and time delaying.It can also avoid the influence and damage on microphone caused by airflow in duct.The cancelling method consists of one loudspeaker and two microphones.The absorbor has quite an absorption to low-frequency noise and narrow band ones.The effective absorption ranges from 50 Hz to 500 Hz.And the optimum index of absorption is about 50 dB to single-frequency noise,18 dB to 1/3 oct band noise and 10 dB to 1 oct band noise.