A:

A low-pass filter attenuates frequencies over a specified cutoff frequency. Miles has a low-pass filter built directly into its mixer.

To set a low-pass filter on a sample, use AIL_set_sample_low_pass_cut_off.

To set a low-pass filter on a stream or DLS sequence, call AIL_stream_sample_handle or AIL_DLS_sample_handle and use the resulting HSAMPLE with AIL_set_sample_low_pass_cut_off.

Finally, you can also use the AIL_set_sample_occlusion function to simulate low-pass occlusion effects. EAX 2 (and later) 3D providers can perform occlusion filtering in hardware. In software-mixing contexts, the AIL_set_sample_low_pass_cut_off function is used to implement occlusion, so the two functions cannot be used together on the same HSAMPLE.