An air handling equipment manufacturer’s perspective on tonal noise measurement and application

Abstract

In order to reliably predict sound from HVAC equipment, including tonal noise, sound power data needs to be determined for each noise producing component in the equipment. Though there are accepted standards for determining broad band sound in resolutions no finer than one-third octaves, there is a general lack of component data regarding tonal characteristics. This noise produced by the HVAC system in indoor environments is often an important source of masking noise improving speech privacy and the overall acoustical environment. The presence of prominent tones that are propagated into the space is counter to creating comfortable acoustical environments. The primary HVAC noise source is the fan and all fans produce tones at the blade pass frequency and harmonics. There is currently no accepted standard method of test for the tonality of fan noise. This paper proposes a standard method that can consistently be used to determine the tonality of fan noise, which can in turn be used to determine if when combined with other self gen noise generated by the air distribution system to determine the prominence of tones that will propagate to the occupied space.