Acoustic diffraction is sometimes discussed with a sense of mystery.

This is, in part, because it is defined negatively: It is the part of the solution to the linear wave equation which remains when the specular approximation is subtracted from it.

There are several ways of conceptualizing acoustic diffraction, and many models,

each approach being best suited to a particular application.

This document is still developing...If does not quench your curiosity, additional resources are at the bottom.

This paper was significant because it was the first time a **transient** solution for diffraction around the edge of a wedge was derived. All prior solutions
assumed the source was **continuous**, or cyclically repeating eternally. This distinction makes the solution appropriate for use in calculating impulse responses applied to
impulsive sources.

The tip of the wedge in the image below is the origin. The edge of the wedge, is the z axis. The edge is finite, and extends from z

The solid angle of the wedge, 360° - θ

Source Position:

In Cartesian Coordinates (x, y, z) = [ , , ] meters

In Cylindrical Coordiantes (r, θ, z) =[ meters, radians, meters]

Receiver Position:

In Cartesian Coordinates (x, y, z) = [ , , ] meters

In Cylindrical Coordiantes (r, θ, z) =[ meters, radians, meters]

The impulse to the right is first order edge diffraction, calculated using the equations below, and reproduced from [2]. The waveform shown is one second in duration.

Which is shorthand for the sum of the following terms:

- This theory can be used to predict the amplitude of noise diffracted around barriers.
- The theory above can be applied to EVERY wedge in a geometry that sound is incident upon, the superposition of all the solutions would give the impulse response of the diffracted field.

- The closer the receiver to the "shadow boundary" that is, the line demarkating the transition between where the specular field is present and is not present, exhibits the largets diffracted contribution.
- The longer the edge of the wedge, the longer the diffracted impulse response in time, this indicates more diffracted low frequency content.
- Both the direct and reflected waves have "shadow boundaries" because the wedge occludes some of the specular field, and the reflected specular field comes from a finite reflector
- The diffracted field changes signs as it crosses each "shadow boundary".

[1] The framework for this page was shamelessly stolen from http://worrydream.com/Tangle/

[2] Medwin, H., Childs, E., & Jebsen, G. M. (1982). Impulse studies of double diffraction: A discrete Huygens interpretation. Journal of the Acoustical Society of America, 72(September), 1005–1013.

[3] JavaScript: The Good Parts by Douglas Crockford. Copyright 2008 Yahoo! Inc., 978-0-596-51774-8

[4] Hart, C. R. (2014). On a combined adaptive tetrahedral tracing and edge diffraction model. University of Nebraska - Lincoln. Retrieved from http://digitalcommons.unl.edu/archengdiss/29/

Assembled in 2014 by Amanda.Blair.Lind@gmail.com