premise: Lead researcher Adrian Houtsma said traditional stethoscopes transmitted and amplified sound that was within the range of human hearing, from about 20 hertz to 20,000 hertz. Most audible sound, including that of the heart and lungs, takes place at around 100 hertz to 200 hertz.
  The ultrasound models transmit a sound signal at 2.3 megahertz into the patient's body. This sound is reflected back to the stethoscope at a slightly different frequency because of the velocity of the internal organs. This is called the Doppler effect.
  The difference in frequencies between the sound wave that is transmitted and the sound wave that is received can be computed to determine the motion of the internal organs. This different frequency is then converted into audible sound.
   What will happen if the sound wave that is received is computed to determine the movement of the internal organs?
hypothesis: sound is reflected back to the stethoscope at a slightly different frequency