When a person hears with both ears the brain can tell where a sound is coming from. But when you have unilateral hearing loss or deafness in one ear judging where noise is coming from is a challenge. Known as the head shadowing effect, having only one working ear can interfere with the surround sound experience normally associated with binaural hearing or hearing with two ears. In the past, a person with unilateral hearing loss would have to position themselves toward the sound source to try and make up for this shadowing. CROS systems have been designed for single sided deafness (SSD) to help reduce this shadow effect.

Unfortunately not everyone with a single sided hearing loss will be appropriate for a CROS or BICROS hearing system. This is why all patients who may be suitable for a CROS system are referred for a full CROS assessment. This ensures they are provided with the most appropriate aiding and amplification for their hearing loss.

CROS stands for Contralateral Routing of Signal. A CROS hearing system takes the sound from the side which has little or no hearing (the bad ear) and will digitally transmit it to the better ear wirelessly. This means the person will not hear sound in the "bad ear ", but they will be more aware of sounds from that side, therefore helping to reduce the shadow effect. The system requires the person to wear two hearing aids, a transmitter on the bad ear and a receiver on the better ear.

A BICROS hearing aid works in the same as the CROS system, but is used where a Patient also requires amplification to their better hearing ear.

CROS/BICROS systems are only available at the University Hospital North Durham or Darlington Memorial Hospital sites via referral from an ENT Consultant.