Final answer:
The statement that echoes have higher signal strength when sound travels through a medium with a lower attenuation rate than soft tissue is true. This is due to the reduced attenuation in the medium, leading to stronger reflected echoes that are detected in ultrasound imaging.
Step-by-step explanation:
The statement provided by the student is TRUE. When sound travels through a medium with an attenuation rate lower than that of soft tissue, the returning echoes from deeper areas can have higher signal strength, known as enhancement. This occurs because the sound waves experience less attenuation, or weakening, in the medium with the lower attenuation rate. In the context of ultrasound imaging, this phenomenon can be observed when the ultrasound waves pass through a medium that offers less resistance to sound waves than soft tissue does, resulting in stronger echoes that are reflected back to the receiver.
At the boundary between two media of different acoustic impedances, as described in the provided information, variation in reflection and transmission occurs. This acoustic impedance difference can greatly affect the intensity of the returning echoes. It's important to keep in mind that constructive and destructive interference patterns, as mentioned in point d., are different phenomena and are not directly related to the enhancement discussed here.