A strap, instrumented to measure stretch, is worn around the chest to detect respiration whilst a subject is at-rest. The resulting signal is contaminated by electrical noise from the mains at 50 Hz with a similar amplitude to the respiration signal. Sketch what the contaminated signal might look like.
The signal is then sampled into a computer. Explain what the resulting digitised signal will look like (using sketches if required) if it is sampled at:
1. 50 Hz
2. 100Hz
3. 500 Hz
What processing should be done on the computer to recover the respiration signal?