This question is for Air conditioning principles and systems

This question is for Air conditioning principles and systems course ( Fourth edition )

You are designing the air distribution portion of the HVAC system for a classroom. You should design the airflows to meet what noise criteria range?___ Draw a sketch showing a flapper check valve and show/explain how it works including the direction of flow.

Solution

Base on typical requirements from different international design standards and guidelines documents, maximum permissible noise levels in class rooms are 30 dBA.

dBA (A-Weighted Noise Level: The sound pressure level determined when using the frequency-weighting network A) The A-weighting network modifies the electrical response of a sound level the same way that the sensitivity of the human hearing system varies with frequency. As the human ear has a non-linear frequency response, it is less sensitive at low and high frequencies and most sensitive in the mid-frequency range between 1 kHz and 4 kHz. The A-weighting is applied to measured or calculated SPLs so that these levels correspond more closely to the response of the human ear