Sound baffle
Encyclopedia
A sound baffle is a construction or device which reduces the strength (level) of airborne sound. Sound baffles are a fundamental tool of noise mitigation
, the practice of minimizing noise pollution
or reverberation
. An important type of sound baffle is the noise barrier
constructed along highways to reduce sound levels at properties in the vicinity. Sound baffles are also applied to walls and ceilings in building interiors to absorb
sound energy and thus lessen reverberation
.
has been available since the early 1970s. The earliest published scientific design of a noise barrier may have occurred in Santa Clara County, California
in 1970 for a section of the Foothill Expressway in Los Altos, California
. The county used a computer model to predict the effects of sound propagation from roadways, with variables consisting of vehicle
speed
, ratio of trucks to automobiles, road surface type, roadway geometrics, micro-meteorology
and the design of proposed soundwalls.
of concert halls, theaters, conference rooms and other spaces where the quality of sound is important. By the mid 1950s Bolt, Beranek and Newman and a few other U.S. research organizations were developing technology to address the design challenges. This design field draws on several disciplines including acoustical science, computer modeling, architecture
and materials science
. Sound baffles are also used in speaker cabinets to absorb energy
from the pressure created by the speakers thus reducing cabinet resonance
.
In 1973, Pearl P. Randolph, a school bus
driver in Virginia
, won a new school bus in a national contest held by Wayne Corporation
for the suggestion that sound baffles be installed in the ceiling of school buses. In 1981, they were first made mandatory by the state of California.
Noise mitigation
Noise mitigation is a set of strategies to reduce noise pollution. The main areas of noise mitigation or abatement are: transportation noise control, architectural design, and occupational noise control...
, the practice of minimizing noise pollution
Noise pollution
Noise pollution is excessive, displeasing human, animal or machine-created environmental noise that disrupts the activity or balance of human or animal life...
or reverberation
Reverberation
Reverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air...
. An important type of sound baffle is the noise barrier
Noise barrier
A noise barrier is an exterior structure designed to protect sensitive land uses from noise pollution...
constructed along highways to reduce sound levels at properties in the vicinity. Sound baffles are also applied to walls and ceilings in building interiors to absorb
Absorption (acoustics)
Acoustic absorption is that property of any material that changes the acoustic energy of sound waves into another form, often heat, which it to some extent retains, as opposed to that sound energy that material reflects or conducts. Acoustic absorption is represented by the symbol A in calculations...
sound energy and thus lessen reverberation
Reverberation
Reverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air...
.
Highway noise barriers
The technology for accurate prediction of the effects of noise barrier design using a computer model to analyze roadway noiseRoadway noise
Roadway noise is the collective sound energy emanating from motor vehicles. In the USA it contributes more to environmental noise exposure than any other noise source, and is constituted chiefly of engine, tire, aerodynamic and braking elements...
has been available since the early 1970s. The earliest published scientific design of a noise barrier may have occurred in Santa Clara County, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
in 1970 for a section of the Foothill Expressway in Los Altos, California
Los Altos, California
Los Altos is a city at the southern end of the San Francisco Peninsula, in the San Francisco Bay Area. The city is in Santa Clara County, California, United States. The population was 28,976 according to the 2010 census....
. The county used a computer model to predict the effects of sound propagation from roadways, with variables consisting of vehicle
Vehicle
A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....
speed
Speed
In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...
, ratio of trucks to automobiles, road surface type, roadway geometrics, micro-meteorology
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
and the design of proposed soundwalls.
Interior sound baffle design
Since the early 1900s scientists have been aware of the utility of certain types of interior coatings or baffles to improve the acousticsAcoustics
Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...
of concert halls, theaters, conference rooms and other spaces where the quality of sound is important. By the mid 1950s Bolt, Beranek and Newman and a few other U.S. research organizations were developing technology to address the design challenges. This design field draws on several disciplines including acoustical science, computer modeling, architecture
Architecture
Architecture is both the process and product of planning, designing and construction. Architectural works, in the material form of buildings, are often perceived as cultural and political symbols and as works of art...
and materials science
Materials science
Materials science is an interdisciplinary field applying the properties of matter to various areas of science and engineering. This scientific field investigates the relationship between the structure of materials at atomic or molecular scales and their macroscopic properties. It incorporates...
. Sound baffles are also used in speaker cabinets to absorb energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
from the pressure created by the speakers thus reducing cabinet resonance
Resonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
.
In 1973, Pearl P. Randolph, a school bus
School bus
A school bus is a type of bus designed and manufactured for student transport: carrying children and teenagers to and from school and school events...
driver in Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
, won a new school bus in a national contest held by Wayne Corporation
Wayne Corporation
Wayne Corporation was a large manufacturer of buses and other vehicles branded with the trade name "Wayne." The corporate headquarters were in Richmond, Indiana, in Wayne County, Indiana, in the United States...
for the suggestion that sound baffles be installed in the ceiling of school buses. In 1981, they were first made mandatory by the state of California.