Final answer:
Speed of sound artifacts in ultrasound occur because the system assumes sound travels through human tissue at 1540 m/s, which is the standard average speed.
Step-by-step explanation:
The speed of sound artifact in ultrasound imaging occurs because the ultrasound system assumes that the speed of sound traveling through human tissue is 1540 m/s. This value is the standard assumption for ultrasound medical imaging, as it represents the average speed of sound through various human tissues. When the speed of sound differs from this assumed value, artifacts may occur in the ultrasound image as the system calculates distances and depths based on the assumption that sound waves travel at 1540 m/s through the body.