The challenge is also related to the limited number
of suitable installation points in outdoor venues,
according to Michele Begotti, project design manager
at RCF’s Engineering Support Group, an Italian
manufacturer of speakers and PA systems. “Open-air
stadia can sometimes be even more challenging than
closed ones because there are often no ‘optimal’
installation points. Locations are typically scoreboards,
light masts, press boxes, or poles beside the tribunes
and it’s not always possible to guarantee clarity of
sound, especially when there’s a lot of background
noise,” he says.
The challenging tasks for system installers include
achieving the correct sound pressure levels (SPL) over
the entire venue. If they fail, it can lead to a lack of, or
non-uniform, sound coverage for certain areas, which
results in a poor signal-to-noise ratio (S/N), or echoes.
If the speakers have to throw sound a long way, which
occurs at many outdoor venues, speaker echoes come
into play once again. Everything has to be calculated
and tested carefully. “For example, if the speakers are at
the rear of the audience it may alter their perception of
sound. But if they’re on masts facing in opposite
directions, it can create different arrival times at the
same level and therefore we get echoes, or image
broadening,” Begotti says.
Recent technical developments have helped to
improve sound at outdoor venues, Begotti reveals. RCF
has adopted systems that use large format compression
drivers and optimize the waveguides and the horns.
They allow the speakers to reproduce frequencies of
AUDIO
GOOD NEIGHBORS
Danley Sound Labs’ speakers are responsible for delivering the
sound at Louisiana State University’s 100,000-plus seater Tiger
Stadium, reputed to be the loudest in the world. But no matter how
loud, the sound will stay within the enclosed bowl. Open-air
venues are sometimes quite different, however. Company
president Mike Hedden explains the challenge can be to prevent
spillage onto adjacent properties.
“It’s an issue for horse racing and motor racing venues,
especially cross-country venues. It’s not easy to get approval if
owners of neighboring properties don’t want hideous noise,” he
says. “There’s a similar issue in the lighting world but it’s easier to
control light pollution using shutters. With acoustics, when
wavelengths are measured in tens or hundreds of feet, you can’t
just put a piece of metal to block sound.”
Danley Sound Labs uses horn-loaded sub woofers that allow the
energy to stay in one direction more than the other. Unlike other
technical solutions that try to cut sound off, it allows speakers to be
quiet at the back and louder at the front. This means it’s possible to
have incredibly high energy sound up to a boundary, then
abruptly cut it off. “We used the technology at the We Out There
Music Festival in Cambridge, England, last year across a multiple
acreage site with a boundary fence. Just like at some sports
venues, the neighbors didn’t want to hear it, especially at night.”
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