Audiokinetic Wwise Knowledge Base

The Low Pass Filter (LPF) is a recursive filter that attenuates high frequencies. It can be applied to Wwise objects and busses at all levels within your hierarchy. It can also be used to help define the radius and cone attenuation of your object positioning.

To maintain performance, Wwise doesn't use all the LPF values. To determine the actual LPF value that will be applied to a sound, Wwise uses the greater of the following two values:

1. The sum of all LPF values in the object hierarchy including LPF values used in RTPCs and states.
2. The higher LPF value between the Radius and Cone attenuation in the Position Editor.

Example - Determining Final LPF Value

Let's say you have the following sound structure using the stated LPF values:

Wwise calculates the final LPF value by taking the greater of the following two values:

• The sum of all LPF values in the hierachy = 15 ((Bus 10) + (Snd 5) = 15)
• The greater value between the Radius and Cone LPF value = 25 (Max(Radius 10), (Cone 25))

In this example, the final LPF value that will be applied to the sound will be 25.

Strategies for Using LPF

The LPF within the object hierachy can be used to create an "artistic" touch or to create an expressive effect associated with a game play event, such as a temporary loss of hearing effect when an explosion occurs near the main character. For Positioning, however, you should use the LPF as a "real-world" effect applied on sound objects where only the highest value is used. In the example above, the LPF filter applied to the Radius would have been insignificant compared to the one applied to the Cone. This is the reason why Wwise keeps only the highest value between the two properties.

Note: Although two LPF values in a series don't sound the same as only the highest one, Wwise only processes one LPF value to maintain performance.