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Theater Acoustics: The Science of Sound

Acoustics is the science of sound. When you learn about acoustics, you will be delving into the hows and whys of sound waves and how they move and behave. Understanding how sound waves travel, how ears detect them, and how the brain interprets them will help you have a firm knowledge about acoustics. Armed with this information, you might use your skills to pursue a career in medicine, research, or even architecture. Theater design is one area in which the construction must rely on science so the sound waves will travel through the air to create the best theatrical experience for the audience.

A mechanical movement creates a vibration of molecules, which transmit sound waves. Sound waves move as molecules vibrate and spread the vibration to surrounding molecules. Sound waves travel through matter, which is referred to as the medium. The type of medium dictates the speed at which sound waves will travel. Scientists know that sound waves travel faster in water than they do in air. Sound waves travel even faster through steel, moving 4,512 meters every second. To be heard, sound waves are processed by the ear. The outer ear is responsible for capturing sound waves and moving them on to the middle ear and the auditory canal. From this canal, sound waves travel through the tympanic membrane to the cochlea in the inner ear. Vibrations convert into electrical impulses in the cochlea, and these travel on to the brain. The auditory cortex in the brain analyzes the electrical impulses to perceive the sounds.

In a theater, the goal is to design the auditorium so that every person in the audience can hear the sounds evenly. Hard flooring or ceiling materials are design features that help sound waves reverberate so they bounce around and travel to more areas of a space. Diffraction is the movement of sound waves around obstacles that are smaller than the size of the sound waves, and this is another factor a theater architect would have to keep in mind. With diffraction, the sound waves wrap around the objects. Meanwhile, an architect designing an open office workspace would need to pay attention to acoustics to prevent sound waves from traveling and keep this area quieter. Adding carpeting, upholstered columns, and curtains can help absorb sound waves to reduce noise.

Acoustical theater design involves an intricate combination of construction materials and the layout of the seating. Stepped seating that gets gradually higher moving out from the stage is crucial for good acoustics because this enables sound waves to bounce off of the graduated surfaces. The materials used in the auditorium are also crucial: Some materials will absorb sounds, while others will diffuse it and disperse it. Fibrous materials absorb sounds effectively due to the friction that occurs as the sound waves make contact with the surface. The thickness of the material is also a factor. Many absorptive panels have an air space immediately behind the outer surface, which improves the absorption of low-frequency sound waves. Upholstered seating and carpeted aisles also will absorb sound. Absorptive panels on the back wall can absorb sound waves after they have moved through the audience, which helps reduce secondary sound waves that bounce around and can cause unappealing noises. Absorptive panels on side walls can help keep the sound waves inside the theater. Having the right amount of reverberation is important as well. Too much reverberation may cause equipment feedback or harsh acoustics. Not enough reverberation can make the sound dull or lifeless.

With the study of acoustics, creating an auditorium with ideal reverberation levels will help ensure that the audience enjoys the performances. It's crucial to have the precise amount of absorption along with diffusing materials in place that will help control secondary sound waves to create a pleasing overall auditory experience. Whether the space will feature live music from orchestras, stage performances that include both speaking and singing, or oratory speeches, proper acoustics will ensure that every person in the audience in every seat in the house hears the performance.