Etymotic Research ETY-COM ER-22 User Manual page 5

Earphone Filter
The ETY-COM headset has a special filter that smoothes the
frequency response and prevents earwax from entering the
earphone. The filter, identified by green acoustic mesh in a small
plastic barrel, is located at the end of the headset and is visible
when the eartip is removed. If the filter becomes clogged it
should be replaced. A dirty filter will reduce or block the headset
output. The need to change filters varies widely among users.
The filter should be changed if the volume decreases or the
sound quality declines.
Changing the filter
1. Remove eartip 2. Remove filter with tool 3. Insert new filter
provided
4. Gently press into place 5. Attach eartip