How can I determine how many signals there are in a mixture?

Let’s say that I have 9 sensors arranged in a 3 by 3 grid. I have multiple objects which emit the same signal and move past the grid of sensors, which are picking up the signals. I have a CSV file which contains readings from the 9 sensors collected every 0.01s for up to a minute and I don’t know how many objects are in there. How can I find out how many there were?

I think each of the 9 sensors will basically collect very similar readings to each other, but at different time-points (since an object moves past each sensor at a different time). Any ideas on a general approach to these sorts of problems would be welcome too!