In this series, we’ll take a look at how certain elements enhance the greatness of a live performance experience, all thanks to science.
PART ONE: ACOUSTIC I - YOU SHOULD BE HEARING WHAT YOU ARE SUPPOSED TO BE HEARING
The key to perfect acoustic is enhancing what you should be hearing and minimizing what you should not.
When buying tickets for a show, everyone strives for a middle seat within f a section close to the stage, but one doesn’t always have the budget or even luck to secure this perfection. Regardless, concert halls (or any kind of auditorium at all) are supposedly designed in such a way, that even the people in the back can still clearly make out the performance: thanks to a (very large) bit of science.
First instinct: in order to be heard, one must be loud enough.
Mics and speakers are great, they increase the maximal distance a sound wave travels before dying out multiple times. Unfortunately, enhancing sound for the audience in a large room is not as easy as turning up the volume of your laptop when you cannot hear a video clearly. Simply pushing the volume of the loudspeakers to maximum results in threateningly loud noise for people sitting near the sound source, whilst possibly missing the purpose of reaching people sitting further away. No one likes sitting in the front row if all they can focus on is the two large speakers bombasting bass notes into their face. Economically speaking, the constant playing of sound at a high volume results in great consumption of energy and likely decreased durability of the machines.
What is considered to be more effective is to instal a sound system of multiple speakers around the venue, each of which directly serve a section of the house, resulting in an equal distribution of sound across the hall. In this case, the volume of each speaker is kept at a moderate level.
As intense as the initial sound might be, what the audience actually hears is still much less.
Just imagine you’re sitting 15m away from the nearest loudspeaker, approximately in one of the middle rows. From the loudspeaker, sound spreads out like a ripple. By the time it reaches the audience, it has expanded out to a radius of about 15m. The intensity of the initial sound has spread out over an area of more than 700 square meters or about 7 million square centimeters, whilst our wonderful ears only collect around 6.5 square centimeters of that ripple of sound each. If you have two functioning ears, the number would make up 13 square centimeters, which is just about 0.00018 percent of it all. This is “direct sound” - the fraction of sound that goes directly to our ears without really meeting anything else.
Let’s say there are 1000 people sitting in the audience, each of them absorbing said 0.18 percent of sound, that adds up to a total of 0.18 percent of the initial being received (and absorbed) directly by the audience. What happens to the other 99.82%? Well, easy enough, it will be received by every other object in the room and it is these objects that will decide for themselves what to do with the sound they obtained. Some will eat it up, some will push it away in another direction.
The job of the acoustician engineers is to utilize this very nature to guide each stray soundwave to precisely where it should be. They shape the walls in ways that sound would bounce right back to the audience in such a short duration of time that it can not be perceived as anything different from direct sound. They install “traffic signs” - the sound panels, with which their intended shapes and materials will tell the sound to either go back to its intended audience or submerge into the walls in order to minimize unwanted repetition.
There are, however, moments of silence in a performance.
It can’t always be loud and grand. There are moments that only require audience and the stage.
Any kind of sound not coming from the cast would interfere with what we want to be hearing. One shouldn’t be disturbed by the loud traffic from the streets, the chattering outside the hall, nor be distracted by the buzzing coming from ventilators or the humming of air-conditioners. And so investments to soundproof a facility should never be questioned for any theatre.
The audience also makes sounds. The oohs, the aahs, the low chattering, stepping, coughing, and even yawning. One member of the audience - all is fine. But multiply each tiny little noise by a thousand is a completely different story. Comfortable cushion seats, therefore, not only ensures the least aching end for your bottom but also serves to absorb most sounds that you make. Aisles and steps are covered in carpets so that even when your favourite high heels accidentally arrive late to the show, they wouldn’t be making more of a statement that they need to be.
Now when you enter your lecture hall or your seminar room, you might want to take a look at the walls, the ceiling and even the material of the floor. They’re not always simply flat and straight up. Appreciate their curves and crooks because there’s been a lot of effort put into the shaping of them all.
Next time, we will take a step deeper into discovering “the voice of the hall”.
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