Why music sounds different - worse - outside

23:40, May 13 2014
OUTDOORS: Venues, such as Wolf Trap's Filene Center in Vienna, Virginia, do not usually have the long narrow shape of a grand concert hall, but there are ways to make the most of outdoor acoustics.

Being outdoors is a wonderful time to sip wine and enjoy the fresh air and music while sitting on your favorite blanket. You know what's not so wonderful at outdoor concerts, though? The sound, which is a problem because that's sort of the whole point.

Walls and ceilings play important roles in how we hear music. They absorb or reflect sound waves, or do a little of both. A sound engineer's central challenge is managing these reflections, because they vastly change the sound being heard. Think of a grand concert hall: long and narrow, with hard surfaces. That's no co-incidence.

"In a concert hall, you hear reflections from the walls and ceilings," says Trevor Cox, a professor of acoustic engineering at the University of Salford in England and author of The Sound Book: The Science of the Sonic Wonders of the World. "Those extra seconds of sound embellish the music and give you a sense of envelopment." In the open air, the sounds drift away.

So how can you make the best of a sonically sub-optimal situation?

For one thing, stick to fast-tempo music. Some genres need reverberance — those reflecting sound waves. Slow-moving pieces benefit from as much as three seconds of lingering sound. It blends the notes together, lending an ethereal feel. That's why cavernous churches with rock-hard, reflective surfaces are great venues for organ music. Fast-paced music such as rock-and-roll and hip-hop need less: You don't want to hear the after-effects of a note when the musicians are already four beats ahead.

Outdoor venues typically have little natural reverberance. The sound waves travel upward and outward without striking anything, and the occasional objects they do strike — such as grass and human flesh — are absorbent. Even if reverb were possible, the sound engineers wouldn't necessarily want to use it. They may have to keep the sound from drifting into nearby homes. They also worry about the weather: In a temperature inversion — when cool air is trapped beneath a layer of warmer air — sound travelling upward can reflect back down onto the audience, fighting with the new sounds coming from the speakers in unpredictable ways. The best tactic under these circumstances is to create a focused beam of sound.

"Flared speakers send music in a particular direction, much like a spotlight," Cox says. "You can arrange different directional speakers to create patterns and limit the sound to a very focused area." When you're caught in a blast of sound like this, you want rock-and-roll or the more upbeat jazz styles. If you must go to an outdoor classical concert, try for something snappy, such as baroque music.

Some outdoor environments lend themselves to better sound than others. The best venue is a sloped seating area, with the stage at the bottom. There's a reason that amphitheatres have been set up that way for thousands of years, and it's not just to help people in the back see.

"Greek amphitheatres are amazing places," Cox says. "They seem to have used the stage area to add reflections off the floor, and raised seats prevent the sound from having to pass through too many heads."

Positioning yourself at a spot with an unobstructed line between you and several speakers will enhance your listening experience. But that's not the only factor to consider when taking in an outdoor concert.

First, don't sit too close to the speakers. The sound they produce is designed to reach people hundreds of metres away, often through several obstructions. Putting yourself just a few feet away is the sonic equivalent of drinking from a fire hydrant.

Next, find the mixing desk. The sound engineer will typically be located about two-thirds of the way between the stage and the back of the audience area. If you sit nearby, you're getting the sound exactly as the engineer thinks it should be heard.

If the sound engineer has been shunted to the side of the stage, you should wander around before deciding where to sit. Different surfaces absorb sound at varying frequencies. (For example, manufacturers stuff car doors with materials that absorb high frequencies, so you get that robust-sounding thud when you close the door, Cox writes in his book.) As you walk, listen for the area with the best balance of bass and treble. It helps to stop and close your eyes occasionally: Our heavy reliance on vision undermines fine listening skills.

If all else fails, at least you have wine.

- The Washington Post