The correct answer is: C. Heart sound
A capacitance microphone is a type of microphone that uses the change in capacitance between two plates to convert sound waves into electrical signals. The plates are typically made of metal and are separated by a small air gap. When sound waves hit the plates, they cause the air gap to change size, which in turn changes the capacitance between the plates. This change in capacitance is then converted into an electrical signal by an amplifier.
Capacitance microphones are often used in medical applications, such as for the detection of heart sounds. They are also used in other applications, such as for the detection of speech and noise.
The other options are incorrect because:
- Heart rate is detected using a heart rate monitor.
- Blood flow is detected using a blood pressure monitor.
- Foot pressure is detected using a pedometer.