# A-level Physics (Advancing Physics)/Digital Processing/Worked Solutions

1. How could the above methods be applied to a digital sound sample?

By taking the median or mean of the sample and the values on either side of it. This would be unreliable, as sound is a wave, so the samples need to vary quite widely. However, something similar could be used when comparing repeating patterns in a waveform.

2. Which of the above methods would be suitable for smoothing sharp edges? Why?

Mean smoothing - median smoothing would not blur the edges.

3. Use median smoothing to remove noise from the following image of a white cat in a snowstorm (the black pixels have a value of 255):

Before
000 255 000 000
000 000 000 255
255 000 000 000
000 000 255 000
After
000 000 000 000
000 000 000 000
000 000 000 000
000 000 000 000

4. Why would mean sampling not be appropriate for smoothing the image given in question 3?

It would produce a really blurred mess, instead of an image, as the noise is too dense.

5. Use mean smoothing to remove noise from the following image of a black cat in a coal cellar:

Before
255 255 255 255
255 255 000 255
255 255 255 255
After
255 213 213 191
255 227 227 213
255 213 213 191