Medicine & Health
How does an ultrasound work?
An ultrasound works by sending high-frequency sound waves into the body and listening for the echoes that bounce back off tissues and organs. A computer times those echoes and turns them into a live image — with no radiation involved.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how an ultrasound works.
Step by step
- 1A handheld probe (transducer) emits sound waves far too high-pitched for humans to hear.
- 2The waves reflect off boundaries between different tissues, fluids, and bone.
- 3The probe detects the returning echoes; the timing and strength of each reveal depth and density.
- 4A computer assembles the echoes into a real-time image on screen.
- 5It uses sound, not ionizing radiation, which is why it's considered safe in pregnancy.
Frequently asked questions
- Is ultrasound safe during pregnancy?
- Yes — it uses sound waves, not radiation, and decades of use support its safety when performed by trained professionals.
- Why is ultrasound used to see babies but X-rays aren't?
- Ultrasound uses harmless sound waves, while X-rays use ionizing radiation that's avoided in pregnancy. Ultrasound also shows soft tissue and movement well.
- What is a Doppler ultrasound?
- A type that measures how the echoes shift off moving blood, letting clinicians see and hear blood flow — useful for checking the heart and vessels.