notch_iir_1894 acting as bandpass in Pulseaudio

[haarp]

Hi,

Either I am going crazy, or something weird is happening. I'm trying to filter out a narrow frequency which is causing bad acoustics (standing waves) in my room. I only need to filter a narrow band around 117Hz. I'm using Pulseaudio, swh-plugins-0.4.17 and notch_iir_1894.

It loads fine: pacmd load-module module-ladspa-sink sink_name=filtered sink_properties=device.description="Filtered_SC203" sink_master="alsa_output.usb-EVE_SC203_Speaker-00.analog-stereo" plugin=notch_iir_1894 label=notch_iir control="117,4.41,2"

It loads, but... does it the opposite of what it should? I'm getting low frequencies and low frequencies only. As if it was a bandpass instead of a notch filter. Huh??

Thanks!

[haarp]

Playing with the center frequency, it seems to be in fact acting as a lowpass. Weird.

Further findings:

• Other plugins work fine in Pulseaudio. I have tested mbeq.
• The notch filter works fine in Audacity. So it has to be a relationship between notch and Pulseaudio. Mhh...

[swh]

I think I've seen other reports of odd behaviours when using plugins in pulse audio, I wonder if there's some subtle bug in their implementation.