Hearing implant maker Cochlear says about 1.9 per cent of registered implants globally of its Nucleus C1500 series devices have failed.

It said the proportion of failure was similar in all three regions of The Americas, Europe, Middle East and Africa, and Asia Pacific.

The C1500 devices were recalled voluntarily by Cochlear in September this year after an increase in failures of its Nucleus C1512 implants, which was part of the series.

In a letter to the stock exchange on Tuesday, Cochlear said that specific microelectronic components, typically one of four diodes, had malfunction because microcracks had allowed water molecules to enter the implant.

The microcracks were caused during manufacturing by variations in process called brazing, which joins the feedthrough to the titanium chassis.

Cochlear, as stated previously, said its Nucleus C124RE and Nucleus C1422 implants were not affected by the failure of the mechanism.