The specular echo originates from relatively large, strongly reflective, regularly shaped objects with smooth surfaces. These intense reflections are angle dependent, and are described by reflectivity equation. This type of reflection is called specular reflection (i.e. IVS, valves).

See also False Distance Artifact, and Scattered Echo.

An echo is defined as the repetition of a sound by reflection of sound waves from a surface.
Echo types used in ultrasound imaging:
Specular echoes are created from relatively large, regularly shaped objects with smooth surfaces. Specular echoes are relatively intense and angle dependent.
Scattered echoes are created from relatively small, weakly reflective, irregularly shaped objects. Scattered echoes are less angle dependant and less intense.

See also Specular Echo, and Scattered Echo.

The dimension of a spectral reflector is greater than the wavelength of the ultrasound beam. With specular echo reflection, the sound strikes the target at perpendicular incidence and the sound is reflected back towards the receiver. Specular reflections produce bright echoes.

Linear scattering occur from specular reflectors or tissue, in which the echo is an accurate copy of the incident ultrasound pulse. If the phase or amplitude of the transmitted sound is altered, the phase or amplitude of the echo will be also altered.
Non-linear scatterers, such as microbubbles, do not follow these rules.

The scattered echo originates from relatively small, weakly reflective, irregularly shaped objects, and is less angle dependent and less intense. The mathematical treatment of non-specular reflection involves the Rayleigh probability density function (i.e. blood cells).