The Challenges of Outdoor Sound

October 21, 2015

People love being outdoors and it’s a part of our natural heritage, from camping trips and family BBQs to large sporting events held under open skies. A concert in the great outdoors offers a unique experience to the crowd, but represents many challenges for the organizers. Sound in the open air needs particular attention. Otherwise, the entire experience can be ruined. High frequencies can be ripped away by the wind and sound needs to reach the whole crowd, but not bother the neighbors. Luckily, there are an abundance of strategies and technologies that can be used nowadays to ensure you consistently get fantastic sound at your outdoor venues.

Account for Mother Nature
Atmospheric conditions make their greatest impact on mid to high frequencies, so ensure you have read the forecast before tuning your equalization settings. If it’s going to be a really windy day, consider that the wind can blow away your high frequencies. If the speakers are directed one way and the wind is coming across that path, there will be a lot of lost high frequencies that won’t reach the crowd so it may be a good idea to have your speakers aligned with the wind direction.

Humidity is another factor that needs to be taken into account as it affects frequencies at 2 kHz and above. The higher the frequency beyond this point, the greater the effect will be. If you don’t have the budget to hire professional staff, contemplate using processor presets. These can be used by less technical employees (of course, with at least a basic understanding of sound) who can press a few keys depending on the weather.

Telemetry
A small outdoor concert doesn’t represent the same sound challenges compared to a large open air stadium or amphitheater. The more sound equipment you have, the higher the chances something is going to fail. You cannot have your employees or worse, an audience member alert you to a misfiring piece of hardware.

If you have the budget for it, consider getting a telemetry system. This equipment will supply to you information for all your remote gear. It will let you know things like a loudspeaker’s temperature, output level and impedance and can go a long way to pinpoint where a problem may occur and resolve the issue before it causes any disruption to your live event.

Mind the Neighbor
When planning an outdoor event, your venue will be rarely surrounded by large open fields, so you need to ensure your sound system does not disturb the surrounding houses, business and other institutions.

First you need to consider who your neighbors are. For instance, are there a lot of historical buildings in adjacent area? In this case, you have to think about the sound effect on insulation-less, single pane windows. You cannot in this case simply crank up the noise, but rather would need to use sound modeling and perhaps loudspeakers on trusses to direct the sound exactly where it needs to be heard.

Another piece of acoustic strategy that will be helpful is using line arrays or column arrays, which basically allow you to direct the sound from your loudspeakers to a more specific area.  The output from a line array or column array is very wide and may be even controlled width with a very narrow vertical dispersion pattern.  When used with trusses they can be lifted and directed at the audience with very little sound going beyond the last rows of the venue.  Line arrays also have increased numbers of high frequency drivers, so this can help over come the high frequency loses do to the wind and weather.

At an outdoor concert, you cannot always accurately predict the weather conditions or stop all sound from reaching the neighbors, but there is a great deal of equipment out there to help you minimize weather-related disturbances to your sound and to direct the sound where you need it to go. Plan ahead as much as you can and direct your sound so the audience can hear it really well but no one else can.

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