how do audio high pass and low pass filters work? (what’s the science behind it?)
In: 5
Assuming you are talking about audio filters due to your post history, but this itself is a topic in a larger subject of signal processing.
**The Math**
There’s a lot of theoretical math behind it, it involves something called the Fourier transform, which takes a signal, say audio, and decomposes it into a sum of waves, which we can then manipulate and remove.
It turns out that electronic circuits can be analyzed using the Fourier transform to see how they would effect the signal going through them. And with this lens, we can also build circuits that manipulate the Fourier transform in certain ways, such as a low pass filter.
**The Electronics**
A simple high pass filter would have the audio signal going through a device called a capacitor. I’m not going to explain how these work, search the subreddit if you don’t know, but what happens is that if a low frequency goes through the capacitor, there is enough time in between the waves to charge the capacitor and it once the capacitor is charged it stops electricity from passing through it. This stops the signal from passing through. For low frequencies, there is not enough time between the peaks to charge the capacitor, so its mostly let through.
To make a high pass filter we can take the same idea and flip it, we connect one side of the capacitor to ground and the other side to the wire carrying the signal. Now high frequencies want to go through the capacitor and as a result go to ground and not to the output, low frequencies on the other hand block the capacitor as mentioned above go to the output instead of being dumped to ground through the capacitor.
Latest Answers