Integrated broadband acoustic attenuator

An acoustic attenuation assembly comprising:

• a low frequency sound attenuation device extending from a first end to a second end and comprising:
• first and second sheets;
• a plurality of webs positioned between the sheets and cooperating with the sheets to form at least one low frequency sound attenuation chamber containing a volume and mass of air, each chamber having an open side;
• a first panel secured to the sheets and closing the low frequency chambers at the first end of the device;
• a second panel secured to the sheets and closing the low frequency chambers at the second end of the device;
• and
• first and second openings associated with each low frequency chamber and through which excited air resonates, the first and second openings extending through the first sheet into each low frequency chamber;
• and
• a high frequency sound attenuation device including a plurality of projections, the high frequency sound attenuation device being formed from a sound absorbing material that absorbs excited air, the high frequency sound attenuation device being secured to the low frequency sound attenuation device to close the open side of each chamber.