The audio filter has an essential acoustic function for the frequency response of the earphones. The purpose of this filter is to deliver sound that matches what one perceives when listening with non-occluded ears. The product comes with two different types of audio filters: the grey filter is for enhanced perception of the mid-frequencies, and the black audio filter for enhanced perception of bass and treble. The grey audio filter is mounted on the earphones by default. Because each individual's perception of sound is unique, Audéo PFE allows you to choose the filter that suits your personal preferences. Another function of the audio filter is to prevent dirt from entering the sound tube.

Make sure that the audio filters are in place before using the earphones. The earphones only function correctly if the audio filters are inserted in the output tube. Replace the audio filters when they become dirty or clogged and you notice the sound of the earphones is affected. Always use audio filters having the same color for both the right and left earphone.

To replace the audio filters, proceed as follows:

1. To remove the ear tips (foam or silicone), grab the ear tip in the middle and pull it slowly until it comes loose.
2. Gently push and twist the "threaded end" of the changing tool into the used audio filter.
3. Do not over-twist the tool; stop when you feel a slight resistance (about one rotation) or you could damage the audio filter. Pull the used audio filter out.
4. So you can reuse the audio filter, insert it in an empty slot in the audio filter box, then turn and remove the changing tool. Dispose of any soiled or damaged audio filters.
5. Proceed with placing a new audio filter in the earphones. Make sure that the audio filter is sitting in the dispenser with the open side facing upwards.
6. Press the "flat end" of the changing tool into the filter ring and pull out vertically. Push the new audio filter into the sound tube of your earphones. Tip the changing tool sideways to release it.