Active noise attenuators have been developed for use in an industrial air duct. A theory is presented for calculating the attenuation of tight‐coupled attenuators, where the microphone and loudspeaker are in close proximity. Practical and theoretical aspects of a tandem system have been developed, utilizing a cascade of two simple monopole attenuators. A theoretical model suitable for use in the computation of the attenuation from both types of tight‐coupled attenuators is presented. The tight‐coupled tandem attenuator can provide a minimum attenuation of 20 dB for more than three and one‐half octave bands from 30 to 330 Hz. Also, the attenuators could provide significant attenuation in the presence of airflow. The attenuation patterns in front of the attenuator loudspeaker are investigated. Good agreement between the measured attenuation and the computed results validates the proposed theory and the model for the calculation of the attenuation from tight‐coupled systems.