Line Source – What is It?

Line Source Road
Line Source Road Traffic

Line Source – What is It?

The behaviour of sound waves emitted by a long, linear source is referred to as line source sound propagation. In this instance, sound waves emanate from the source along a line or narrow segment, as opposed to a single point.

In consultancy, the most common form of a line source we encounter is continuous road traffic on a road. Note that single vehicles on a road act as a point source (see the previous blog ), however a continuous stream of traffic averaged over a time period acts as a line source. See a later blog on CRTN (Calculation of Road Traffic Noise) which will be published by us in October, that will help unravel some road calculations.

When sound is emitted from a line source, such as a road, continuous row of speakers or a vibrating string, the sound waves travel in a cylinder-shaped pattern. In contrast to the case of a point source, the wavefronts formed by the sound waves are cylindrical surfaces.

Understanding sound propagation from a line source is essential for designing and optimising sound systems, particularly in large spaces where uniform coverage is desired. By analysing the characteristics of line source propagation, professionals can determine the optimal placement, orientation, and configuration of line arrays and distributed speaker systems to accomplish the desired sound distribution and coverage in a given environment.

Key characteristics of sound propagation from a line source include:

Cylindrical Wavefront: Sound waves originating from a line source are characterised by a cylindrical wavefront. This indicates that the waves propagate equally in all directions perpendicular to the line source, resulting in a cylinder-shaped distribution of sound energy.

In contrast to a point source, line source sound propagation exhibits an asymmetrical pattern of sound distribution. The sound energy is more concentrated in directions perpendicular to the source line, while the sound level decreases in directions parallel to the source line.

The falloff rate of sound with a line source is gentler than for a point source, it being 3dB per doubling of distance rather that 6dB per doubling of distance for a point source.

Reduced Intensity Variations (nodes): Compared to a point source, line source sound propagation typically results in diminished intensity variations within the listening area. This is because cylindrical wavefronts distribute sound across the coverage area more equally.

If you would like to learn more, please contact a member of the CSG Acoustics team and we will be happy to assist you.

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