Open Earmoulds for Hearing Aids
Open moulds are used for both high frequency and low frequency (up to 1KHz) hearing loss. They offer the largest possible vent to allow the low frequency to pass through naturally. The high frequency is amplified through the remaining canal portion of the mould.
The vent is achieved in three different ways:
1. D-type - Most of the canal portion is removed allowing just enough to accommodate the tube.
2. E-type - Canal is left in tact with the largest vent possible
3. F-type - Canal is completely removed leaving only a small portion to show canal direction.
Retention can be achieved in three different ways:
1. Ring- Skeleton-type retention with the whole band in tact
2. Gap- Phantom-type retention with part of the band removed
3. Claw- Bridge in the crux area is removed
The suggested method for selecting the most suitable open mould is to choose the vent type (D, E or F) followed by the retention style (Ring, Gap or Claw).