Effects of parameters of HVAC noise on subjective preference and intellectual productivity

Noise induced by a heating, ventilation and air conditioning (HVAC) system is an important factor that affects the comfort of our living space. Much effort has been devoted to reduce HVAC-noise levels, however, the reduction of the noise levels beyond a certain level sometimes cause a relative rise of the secondary noise sources and a loss of operation feeling. Therefore, there is a need for a novel method to design "comfortable" HVAC noises. On the other hand, comfortable sounds sometimes elicit not only relaxation but also decrease of vigilance. Consequently, comfortable sounds may deteriorate the intellectual productivity. The present study investigated effects of some acoustical parameters (loudness, sharpness, and dominantfrequency- peak amplitude) of HVAC noise on the preference and the intellectual productivity. First, effect of the parameters on the preference of each subject was measured using a paired comparison on a seven-point scale. The preference was improved as the loudness and dominantfrequency- peak amplitude decreased. Next, the intellectual productivity was measured using Kraepelin test during each subject listened to the most- and least-preferred HVAC noises. The intellectual productivity for the most-preferred noise was larger than that of the least preferred. These result provide useful information to design well-balanced or tailor-made HVAC noises.