architectural acoustics (redirected from Concert Hall Acoustics)

architectural acoustics [¦är·kə¦tek·chər·əl ə′kü·stiks]

(civil engineering)

The science of planning and building a structure to ensure the most advantageous flow of sound to all listeners.

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Architectural acoustics

The science of sound as it pertains to buildings. There are three major branches of architectural acoustics. (1) Room acoustics involves the design of the interior of buildings to project properly diffused sound at appropriate levels and with appropriate esthetic qualities for music and adequate intelligibility for speech. (2) Noise control or noise management involves the reduction and control of noise between a potentially disturbing sound source and a listener. (3) Sound reinforcement and enhancement systems use electronic equipment to improve the quality of sounds heard in rooms.

Room acoustics

One essential component of room acoustics is an understanding of psychoacoustics and the qualitative evaluation of sounds heard by people in rooms. Psychoacoustics is the study of the psychology of sounds. It includes studies conducted in laboratories and in actual listening rooms of how people react to the level, frequency content, direction, and arrival time of sounds. These studies have established a set of relationships among the acoustical qualities that have been found to be important in the perception of sound, the room surfaces that contribute to these qualities, and the physical components of the sound field in a room that contribute to these properties.

Several important design concepts are used to provide good listening conditions in rooms for speech and music. First is to provide good access to the direct sound for all people in the room. This usually involves raising the source of sound on an elevated stage, altar, or podium at the front of the room and sloping the floor surface to elevate the ears of people above the heads of those seated in front of them. The width and depth of the room should also be limited so that the natural direct sound can project from the speaker or instruments at the front of the room to the listeners. Second is to limit the background noise level in the room so that people can hear the sound they want to hear above the level of the ambient sound. Third is to limit the reverberation time in the room so that sounds are heard clearly and fully, while providing enough reverberant sound energy that sounds are heard as “full” and “live.” If there is too much reverberation in a room, the persistence of an initial syllable will cover up or mask the one that follows it, making it difficult to understand what is being said.

Noise control

Acoustical planning concepts for buildings include placing noisy activities away from activities that require relative quiet and locating noise-sensitive activities away from major sources of noise. Buffer spaces such as corridors or storage spaces are often used to separate two rooms that require acoustical privacy such as music rehearsal rooms in a school. Intruding noises from the exterior or from adjoining rooms can be reduced by using walls, ceilings, windows, and doors with appropriate transmission losses. A compound or double wall assembly can be used to reach a relatively high transmission loss with low mass per unit wall area. The separation between the two leaves or surfaces of the wall must be maintained as completely as possible for this to occur.

It is essential to control noise from building services. The location of air-conditioning plants on a site should be chosen so as to reduce propagation of noise to neighbors. Mechanical rooms in buildings that house air handling units, pumps, and other equipment should be located away from noise-sensitive rooms. Noise control treatments in the air-conditioning system include providing vibration isolators for equipment; providing flexible connections between ducts, conduits, and pipes to equipment; designing air ducts to operate with air velocities that will not create turbulent flow noise; and installing silencers or attenuators in the ducts to reduce noise produced by fans from traveling through the duct work. See Mechanical vibration

Sound reinforcement

Sound reinforcement systems, electronic enhancement systems, and sound amplification systems are used in many buildings. A sound reinforcement system amplifies the natural acoustic sounds in a room that is too large for people to hear with just “natural” room acoustics. This type of system reinforces the natural sounds that come from the room, increasing their apparent loudness with a series of loudspeakers.

In an electronic enhancement system, loudspeakers act as virtual room surfaces to create the perception that sounds are reflected from these surfaces at the proper times and with the proper loudness. These systems usually have a network of loudspeakers located throughout a room and connected to a microprocessor. The microprocessor can delay the signals to arrive at times corresponding to reflected sounds from the virtual room surfaces. It can also add reverberation and other special acoustic effects to create a virtual acoustic space.

A sound amplification system makes all sounds played in a space louder. It is usually not designed to supplement the natural room acoustics or to provide subtle virtual room effects to the amplified sounds.