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The Impact That Acoustics Can Have On Sound In Any Room

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The Impact That Acoustics Can Have On Sound In Any Room

By Pat Brown • July 22, 2019

For most humans, there is nothing easier than breathing, seeing, smelling and hearing. We do these things without thought, and even take them for granted.

Our senses were given to us to help us exist in a physical universe. They are transducers that allow physical stimuli to be converted into a form recognized by the brain. We are bombarded with stimuli every waking moment, and our brains are continuously processing the information to help us function in our environment.

Of all of the senses, many researchers are the most amazed by the sense of hearing. In fact, more is known about how the eyes work than the ears. While the act of hearing is quite simple, attempts to quantify and understand the processes involve mathematics and physics at the highest level.

Acoustics, simply, is the study of vibration. Architectural acoustics is the more specific study of air vibrations in enclosed spaces. Sound travels in waves, and these waves interact in a complex way with the environment.

We usually think of sound waves as simply bouncing off of objects, but in fact the behavior of sound upon an encounter with a physical object can include reflection, absorption, refraction, diffraction and scattering – in any combination.

It is the complex combination of these behaviors that determine what something sounds like.

Hardly An Accident

Acousticians are concerned with two major areas. The first is how sound behaves in an enclosed space, and the second is how that behavior is perceived by human listeners.

The study of sound behavior involves measuring sound to quantify it – describing it objectively with numerical scores and values. It may also involve predicting its behavior. That’s the biggest challenge and where the real fun starts.

If we can predict sound behavior with reasonable accuracy, then we can determine in advance whether a proposed building will sound like a great concert hall, a large garbage can, or somewhere in between.

A good sounding room is hardly ever an accident, and it is a sad fact that the construction methods and materials used in the Western world usually produce bad-sounding rooms. Materials such as plaster, glass, painted block, steel and wood are very reflective. Excessive use of these materials in large spaces is a recipe for sonic disaster.

We have all been to the high school gym or convention center that is an acoustic nightmare because of the lack of acoustical treatment. Unfortunately, relatively few people have been to a great concert hall that is an acoustical wonder and a joy for listening.

The common denominator of the great concert halls of the world is that they were all designed by competent acousticians that had a large enough budget to do it right.

About 70 percent of any sound that we hear indoors has reflected off of one or more objects before it arrives at our ears. This means that even a good sound source, like a fine violin or a high-quality loudspeaker, can sound bad if the reflected field is less-than-optimum.

To gain an appreciation for the significance of a room’s acoustics on what we hear, take a few minutes to perform a simple test. You probably do this every day, but if you’re like most folks, you probably haven’t been paying attention to the results.

The test: take a walk through a large building and listen to the sound of your footsteps as you move from room to room. Move from a small room to a big room. Walk down a hallway. Walk through a large meeting room or gymnasium. Finally, walk outside.

As you listen, you’ll find that the differences are dramatic! Words like “live,” “dead,” “bright,” or “dull” might pop in your head as a way to describe what you heard. Then, do the test again while conversing with a colleague, and listen to both voices. You’ll quickly see why room acoustics is important, even vital, to a pleasing listening experience.

It could be argued that none of the sounds that were heard were actually your shoes hitting the floor or your natural voice. Most of what was heard was reflections that the room produced in response to an acoustical stimulus.

And after this test, you’ll never be able to ignore room acoustics again. Sorry about that! It’s called the Catastrophe Effect. A lifetime of study would be required to understand why each room sounded different, let alone which ones sounded “good” and which ones sounded “bad.”

Clearly Defined?

Most things in the world around us have an example of perfection that can be used as a standard to by which to judge other things. An atomic clock can be used to resolve arguments about the correct time. A platinum iridium one-meter bar at the American National Standards Institute could be used to resolve arguments about correct length.

Yet there are no acoustical standards – no perfect loudspeakers, microphones or rooms. Because of this, sound is often considered to be subjective, where beauty is in the eye (ear) of the beholder, like music or a painting. Yet clearly “good” and “bad” sound does exist, and we want our auditoriums and sanctuaries to sound pleasing to all who visit them.

Acousticians are tasked with dealing with the subjective and objective characteristics of sound to make the room sound “good,” even though “good” is not a clearly definable objective.

One thing is for certain. Bad acoustics in the form of room reflections and excess noise can render a space virtually unusable for speech communication and music playback. I work in such spaces all the time – they are the reason I can make a living in the sound business.

It’s also interesting to note that many of the worst sounding rooms are produced by some of the most highly respected architects. These spaces are often visually stimulating yet sonic disasters.

Clearly a balance must be struck between efforts to make a room beautiful and efforts to make it sound good.

While these two goals are not mutually exclusive, they often work against each other. If we hold the view that an “auditorium” is “a place for hearing,” then room acoustics must be taken into consideration – not just the sound system!

SynAudCon offers “Audio Applications – System Optimization & EQ” as web-based training. Click the link to see the related article.

More articles by Pat Brown on PSW:
How To Illuminate The Audience With Beautiful, Consistent Audio Coverage
Proper Loudspeaker Placement: How To Avoid Lobes and Nulls
Ten Reasons Why Church Sound Systems Cost More
What Makes A Quality Loudspeaker?

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