Described herein are noise attenuating ducts and vehicles using these ducts for environmental control systems. A duct comprises an exoskeleton structure and a sound-absorbing structure, disposed within and conforming to the exoskeleton structure. The exoskeleton structure provides external mechanical support to the sound-absorbing structure thereby helping to maintain the tubular shape of the sound-absorbing structure. This external support does not interfere with the airflow inside the sound-absorbing structure. Furthermore, the external positioning of the exoskeleton structure allows the integration of various support mounting features for the installation of the duct in a vehicle. In some examples, the exoskeleton structure comprises a plurality of enclosed openings to reduce the weight of the exoskeleton structure and provide additional flexibility. Furthermore, additive manufacturing of the exoskeleton structure allows achieving a monolithic structure with various features and characteristics described above.