The Opera house required NC-25 despite the air handling unit installation in the attic directly above.

PROBLEM: Compounded problems The addition of air conditioning to this retrofit opera house project was a tough act. Low frequency noise could break out of the air handling unit casing and connecting ductwork. Also there was no straight run of duct connecting to the AH unit at both the supply and return.

SOLUTION: Package supply Vibro-Acoustics accepted the responsibility for the performance of the unit and guaranteed the combined supply, return and unit breakout noise would not exceed NC-25. The AH unit consisted of 16,000 CFM supply and return plenum fans, 4” acoustic panel walls and roof, supply and return ‘T’ silencers, mixing box, heating and cooling coils etc. To prevent breakout noise, AH unit panel walls were 12 gauge, supply silencers 16 gauge, outer casings and return silencers 18 gauge.

The unit was designed to ensure all components fit through existing openings. For ease of assembly, the unit was made in 4 sections and bolted together on site with 4 flanges.