In early 2008, a newly constructed six level car parking building at a private hospital in Christchurch, New Zealand was the cause of complaint due to a tonal noise audible during windy conditions. Subjectively the noise was “like someone rubbing their finger around a crystal wine glass”. A review of literature suggested that the noise could be generated by an aero-acoustic tone generated by wind flowing either over a thin obstruction or into a slot. The building had two different types of balustrades and a number of thin slots, however the external balustrades were considered to be the most likely cause of the tone, due to their location where they were subjected to high wind velocities. The external balustrades were constructed from 36 steel balusters of dimensions 50mm x 6mm x 1050mm. The balusters were arranged vertically and spaced at 93mm centres. 70 balustrades were located in the building.