An earlier research study sponsored by ASHRAE on the "Determination of the Relationship between Low Frequency HVAC Noise and Comfort in Occupied Spaces - Objective Phase" by Broner (1994) suggested that three factors are important in determining the subjective response of people to low frequency HVAC noise. These, not necessarily in order of importance, were overall level, spectral imbalance and amplitude and temporal modulation effects. The report also recommended psycho-acoustic testing to investigate these parameters with a goal of determining the most appropriate low frequency metrics for assessment of low frequency HVAC noise.

This report describes in detail the implementation and methodology used for the Phase 2 Psycho-acoustic testing. Noise stimuli for use in the testing were chosen from and based on the measured stimuli collected in the Phase 1 Study. To assess and rate the psychological attributes of loudness and annoyance of the noise stimuli, the magnitude estimation task was used to rate the noise stimuli. Assessments of relief-on-cessation of the stimuli and un-acceptability were also collected. This report details the results and draws conclusions with respect to the derivation of the most appropriate low frequency metrics for assessment of low frequency HVAC noise. The report also recommendss future research work.