Unlike regular sound, ultrasound can be directed into a single direction. The echoes received by a stationary probe will result in a single dimensional signal showing peaks for every major material change.
To generate a 2D picture, the probe is swiveled, either mechanically or through a phased array of ultrasound transducers. The data is analyzed by computer and used to construct the image. In a similar way, 3D pictures can be generated by computer using a specialized probe. In this way, a photo of an unborn baby may be made.
Some ultrasonography machines can produce color pictures, of sorts. Doppler ultrasonography is color coded onto a gray scale picture. From the amount of energy in each echo, the difference in acoustic impedance can be calculated and a color is then assigned accordingly.

See also Densitometry and 3D Ultrasound.

Duplication artifacts can be created through diffraction and refraction on interfaces, also if the acoustical impedances of tissue is too much different and the ultrasound is reflected multiple on tissue layers, where the detected echo does not come from the shortest sound path.

See also Mirror Artifact.

Reverberation artifacts are produced from the multiple reflections from an object if the acoustical impedances of tissue layers are too much different and the detected echo does not run the shortest sound path because it bounces back and forth between the object and the transducer. In a reverberation artifact, the sound wave is reflected back into the body from the transducer-skin interface.

The amplitude is the signal height. The amplitude of the ultrasound echo is proportional to the difference of the acoustical impedance caused by different tissue layers. The amplitude decreases with increasing penetration depth of a homogeneous tissue.

See also Color Amplitude Imaging.

The dead or ring down zone is the distance from the front face of the transducer to the first echo that is identifiable. The signals from this region are unsuitable. The dead zone is the result of transducer ringing and reverberations from the interface between the transducer and the scanned object. Impedance matching between the transducer and the receiver is important to avoid electrical ringing.
With an increase of the frequency, the pulse length and the depth of the dead zone decrease, if all other parameters remain constant. The acoustic power also affects the depth of the dead zone.