We use duct liner or the insulation sheet in our units to reduce the sound from the unit to the surrounding.
When doing a sound test we have noticed a spike at frequency of 1000 Hz on the noise criteria (NC) chart ( Sound pressure level vs frequency chart)
What could be the possible cause of this spike at 1000 hz. As 1000 hz is the most important frequency. Could it be the scroll compressor (42 MBH)
As of now the insulation that we use has a sound absorption coeiffient of 0.5 at 1000 hz. As we know that closer to 1 is better sound absorption.
Apart from using better sound absoprtion insulation is there any thing else that could be done to reduce this spike.
Which refrigeration equipments produces this spike
Please note the spike is not that much. Say at 500 hz it shows NC 35 and then at 1000Hz it jumps close to NC40 and then comes down close to NC 35Hz at 2000Hz