What does low pass filter mean?

A filter that lets slow changes in a signal through and smooths away fast ones, such as sensor noise. The exponential filter, filtered = alpha * raw + (1 - alpha) * filtered, is the simplest; more smoothing always means more delay.

Also written as: low pass filters, low-pass filter, low-pass filters, exponential filter, exponential filters

In a lesson

Each new reading gets weight alpha; everything before it keeps the rest. The weights decay geometrically into the past, which is why it is called an exponentially weighted moving average, and in signal processing it is a first order low pass filter.

Learn it

• Taught in U4.3 The low pass filter Noise and filtering, University

Used in

• A7.8 Sound and MIDI
• U4.5 The price of filtering
• U4.6 Choosing the filter
• U6.2 Predict and correct
• U6.3 The Kalman gain

All glossary terms