A contralateral routing of signals (CROS) hearing aid is a type of hearing aid

Hearing aid

A hearing aid is an electroacoustic device which typically fits in or behind the wearer's ear, and is designed to amplify and modulate sound for the wearer. Earlier devices, known as "ear trumpets" or "ear horns", were passive funnel-like amplification cones designed to gather sound energy and...

 that is used to treat unilateral hearing loss

Unilateral hearing loss

Unilateral hearing loss or single-sided deafness is a type of hearing impairment where there is normal hearing in one ear and impaired hearing in the other ear.-Signs and symptoms:Patients with unilateral hearing loss have difficulty in...

. It takes sound from the ear with poorer hearing and transmits to the ear with better hearing.

Systems can involve two behind-the-ear units connected either by wire or by wireless transmission. There are also systems incorporated into eyeglasses. BAHA

Bone Anchored Hearing Aid

A Bone-anchored hearing aid is a type of hearing aid based on bone conduction. It is primarily suited to people who have conductive hearing losses, unilateral hearing loss and people with mixed hearing losses who cannot otherwise wear 'in the ear' or 'behind the ear' hearing aids...

CROS systems use the conductivity of the skull to transmit sound.