Digital Filters

Smoothing away the noise

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• A moving average is a simple low-pass filter: it keeps slow trends and suppresses fast jitter.
• Choosing the window trades noise against distortion.
• Filters are weighted sums of samples (convolution): echoes, reverb, hum removal.

Steps

1. An average of neighbours
2. Tune the filter
3. Filters and frequencies
4. Echoes and reverb
5. Differences, not averages
6. Averaging away a frequency