Prince's Island Park
In 1998 we worked with the Calgary-based acoustical consulting firm Faszer Farquharson & Associates Ltd. in an effort to help both the City of Calgary Parks Department and the Calgary Folk Festival Society mitigate community noise complaints that arose during the 1997 Festival. The festival is held on Prince's Island in the heart of downtown Calgary. The island park stage is located within 100m of several high rise condo/apartments to the south and within 300m of a residential neighborhood to the north. The complaints were coming from areas immediately south and to the north and west, down range from the stage. Certain atmospheric conditions in the river valley would occasionally make the festival audible several kilometres to the west along the valley due to focusing or reflection from inversion layers, so controlling the forgotten half of the sound energy above the speaker array axis would also be an important issue.
We developed computer models of the coverage of the loudspeaker arrays that allowed us to provide information on the overall array directivity and octave band sound power to FF&A. They used this information to model the impact on the surrounding community using an Australian software package designed for community noise work.
We also modeled several possible options for modifications or adjustments to the rental loudspeaker systems provided by the rental sound company that would help reduce levels off island. The options that were implemented included a basic downtilt of the tower mounted front arrays and the infill tower delay loudspeakers, and spacing of the subwoofer arrays. In most concert box arrays, there is as much sound energy radiated above the axis of the speaker array as below, so if the boxes are aimed straight out from the tower, there is as much sound energy being sent up and into the community as there is being sent to the audience. A quick way to reduce the sound level in the community is to stop aiming sound into the community.
By modeling several variations in subwoofer spacing we were able to get a predicted drop in level of 10dB+ at right angles to the stage. This low frequency null zone coincided with an entire apartment building.
A few elements of the system layout and configuration had to be adjusted through the three days of the festival to provide enough level for the patrons at the far west end of the field. These adjustements were made by the sound company personnel. Through a combination of loudspeaker tilting, aiming, level adjustment and ongoing control and monitoring by the sound company, we were able to help the Folk Festival reduce levels off the island which did all but eliminate complaints from the community.
We also found that the variations in the loudspeaker coverage (approximately 6-8dB) made these coverage hotspots, or lobes, audible above the background ambient noise level in the community at double the distance that the general show levels were audible, in this case at distances approaching 800-1000m. The lobes are created from the interaction between loudspeakers in the array. This is yet another reason why it is so important that loudspeaker systems have smooth and uniform coverage, even in an outdoor concert setting. The 3D coverage models that are popped up by the link above were modeled in EASE 3.0 using a 3 wide x 2 high array of popular concert sound boxes in a straight, untilted array.
Collaborating Consulting firm:
See the 2002 permanent stage solution
Mc Squared System Design Group, Inc
323 - 901 West 3rd Street
North Vancouver, BC V7P 3P9
Phone 604 - 986 - 8181