Good acoustical design encompasses controlling all aspects of sound entering, leaving, or being generated within a space. Desirable sounds, such as speech, music, or other communication, are best received if the spaces where they originate are designed to help them resonate clearly. Unwanted sound from outside of a building can be distracting or even harmful to people inside. Sound flowing between rooms or spaces in a building in all directions (i.e. through walls, floors, ceilings, etc.) can create similar negative indoor experiences. All of these aspects of sound in a building are important to a successful design much the same way designing a building to use desirable light while controlling undesirable glare is important. By taking a holistic approach to acoustical design as an integral part of architectural and interior design, a comprehensive, successful result can be achieved.

Sound Principles: Acoustic Basics

Sound is energy that radiates from a source. It moves through the air just like other energy does (i.e. heat energy or light energy) which means that it can move through air-filled openings in buildings too. Sound energy can also penetrate a wall, ceiling, or floor similar to the way heat does. Professionals, specialists, and scientists have studied sound in terms of its generation, its transmission through space (airborne sound) and objects (structure-borne sound), and its reception by people. As such, a significant body of knowledge is available on how to deal with sound in human environments as part of the field we know as acoustics or acoustical design.

Sound is typically characterized both by loudness and frequency. Loudness is measured in decibels (dB) such that the higher the dB rating, the louder the sound. The commonly referenced range is 0 dB (threshold of hearing) to around 130 dB (threshold of pain) with human speech being in the middle at around 50 to 65 dB. Sound frequency, meaning the time frequency of the radiating waves of sound, is measured in Hertz (Hz). One Hz is equal to a frequency of one cycle per second. The human ear can typically hear frequencies or sound “pitch” between about 20 Hz (very low-pitched, bass sounds) up to around 20,000 Hz (very high-pitched, piercing sounds) if the person is fairly young—older adults may hear frequencies up to about 15,000 Hz. Sound exists above and below this range, but our ears don't hear it, unlike some animals such as dogs or bats that do indeed hear very high-pitched sounds (over 20,000 Hz) or elephants that can hear lower sounds (below 20 Hz).

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Addressing the total acoustic and aesthetic design of a space will help assure a positive experience for the users and improved indoor environmental quality all around.