Open moulds

These come in a variety of types and are suitable for high frequency hearing losses where the low frequency hearing is normal. Open moulds will not normally be suitable if high powered hearing aids are required as there will be feedback problems. There are three different types of custom open moulds, D, E and F available in gap, claw or ring retention styles (the choice between gap, claw or ring being largely patient preference). The acoustic changes that an open mould fitting can achieve will be influenced by the type of vent style that D, E or F carry.


D (Half the meatus is cut away)

This consists of a canal portion which just covers the sound tube. The canal has a very large vent which will reduce low frequency amplification whilst allowing low frequencies to pass through to the ear drum naturally.

 Open Mould D.jpg


E (No modification to the meatus)

There is no outward modification to the meatal portion but this option has the largest possible vent parallel to the sound bore. It has a similar effect to the type D open mould in reducing the low frequencies, perhaps to a lesser degree than types D or F.
Open Mould E.jpg


F (Meatus removed to concha level)

F has a similar vent opening to type D but consists of a very short canal portion, trimmed to concha level. The effect of a short tip may mean retention of the mould is more difficult. It should reduce the low frequency amplification to the greatest possible extent and a short canal will also enhance the passage of high frequency sound. This is suitable for CROS (Contralateral Routing of Sound Signals) fittings.

Open Mould F.jpg

Further information

Earmould products

Earmould material selector

Earmould options guide

Product codes


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