Many people have had the experience of sitting in the back of a large auditorium and being able to hear what is spoken on stage even when there is little, if any, sound amplification. Others have been in much smaller spaces, seated much closer to a speaker or performer, and yet have been unable to hear what is going on up front. Why this difference? The answer lies in the acoustics of each space.
Acoustics is a science that has to do with measuring the transmission of sound waves. Although the discipline covers waves in solids, liquids, and gases, most people are likely familiar with acoustics through the application of the science to architecture. A theater or other building with good acoustics allows sound to travel naturally for long distances, enabling people to hear music, a play, or something else even if they are sitting far away from the stage. On the other hand, buildings with poor acoustics do not allow the sound to travel very well from one side of the space to another. No matter how loud a performance or other event happens to be, people who are attending it will have trouble hearing it if the acoustics are bad.
A theater or other building with good acoustics allows sound to travel naturally for long distances, enabling people to hear music, a play, or something else even if they are sitting far away from the stage. On the other hand, buildings with poor acoustics do not allow the sound to travel very well from one side of the space to another. No matter how loud a performance or other event happens to be, people who are attending it will have trouble hearing it if the acoustics are bad.
The field of acoustics is actually one subset of the larger discipline of physics. 
Whether people are enjoying a performance from the comfort of a well-designed and enclosed auditorium or they are sitting in an outdoor theater, their ability to hear what is going on will only be as good as the quality of the architectural acoustics and the ability to transmit sound waves in the building or structure. Acoustics takes into account the generation, propagation, reception, and effects of sound waves in a particular space, and architects and builders rely on acousticians to either reduce the distance that sound will travel or increase it. In a library, for example, an acoustician’s goal is to minimize the transmission of sound waves so that people can study in comfort and not get distracted. The goal is exactly the opposite in rooms that must accommodate large crowds that are viewing a performance or lecture.
Perhaps the best way to understand acoustics in action is to consider the theaters of ancient Greece. Thousands of years ago, there was no such thing as electronic sound amplification, so builders had to figure out a way to build theater structures that would allow the sound from a performance to extend all the way to the back of the Greek amphitheaters where it was conducted. They did this by employing stepped seating arrangements like those that are still used today for stadium seating at movie theaters and other venues. The first row of seats was on the same level as the stage, the second row a little higher, the third row a little higher than the second row, and so on, all the way to the back of the theater.
Why was such stepped seating so good for theater acoustics in ancient Greece? The answer lies in the way that sound waves bounce off of stepped or corrugated surfaces. In such structures, low-frequency sounds are minimized.
Thus, background noise such as the breeze blowing was minimized and the sound waves coming from the front of the theater during a performance could be heard from the comfort of all of the rows of the theater’s seating.
Sound waves are either absorbed by the material that they strike or are reflected out, bouncing off of a material. The key to sound acoustics is striking a balance between construction material and layout that will allow sound waves to be absorbed or reflected in an optimum way for the purposes of the building that is being designed. The key is to select materials and designs that screen out the wave frequencies that are not desired in a space while amplifying those that the space is designed for. Thus, recording studios are well-insulated with sound-dampening panels so that outside noise cannot get in while recording is happening.
A theater may lack such things in order to help everyone in the building hear a performance, but if the theater is one of many in a structure, sound-reduction materials may be integrated into the design to keep the sound traveling well in the auditorium without letting sound escape through its walls.
Acoustics is a valuable science that has many practical applications. For more information on acoustics that can be studied from the comfort of your home or office, consult the following sources:
- Acoustics for Music
- Acoustics and Vibration Animations
- Acoustics and You: Careers
- An Acoustics Primer
- Architectural Acoustics: The $20,000,000 Mistake
- Architecture for Acoustics
- Basic Acoustics
- Built for Sound: Architectural Acoustics
- Engines of Our Ingenuity: Acoustics
- Fundamentals of Architectural Acoustics
- Introduction to Acoustics
- Judging Auditorium Acoustics
- Room and Auditorium Acoustics
- The Origins of Building Acoustics for Theatre and Music Performances
- What Is Acoustics?
- Why the Greeks Could Hear Plays from the Back Row
