Question

1.What is the source of the speckle seen in an ultrasound image?

2.Why is speckle not considered noise?

Answer 1

Ultrasound is usually used to internal organs, skin, muscles etc.
Speckle is a noise which arises during ultrasound, tomography etc.
It is usually caused when coherent processing of many backscattered signals.
It arises basically because of interference of returning wave.

Despite some interference caused results in speckle, it is not considered as noise.
It is just considered as interference pattern.
Specially in ultrasound, speckle is not random and also helps in determining boundaries.