Most hearing aids work on the same basic idea: pick up sound near an ear, process it, and deliver it into that same ear. CROS and BiCROS systems do something different. They move sound from one side of the head to the other. This article is a plain-English explainer of how that works, written as general information rather than as advice about any individual's hearing.
What the Letters Stand For
CROS stands for Contralateral Routing of Signals. In plain terms, contralateral means "opposite side" and routing of signals means sending sound across. BiCROS is short for Bilateral Contralateral Routing of Signals. The idea is the same in both: sound arriving on one side is picked up there and sent to an ear on the other side. The Department of Health uses the same expansions in its provider notices.
How a CROS System Is Put Together
A CROS system has two parts. RNID, the UK charity, describes them as a conventional hearing aid worn on one ear and a microphone-style device worn on the other, which looks like a hearing aid but works as a sound pickup. The pickup unit collects sound on its side and sends it wirelessly to the device on the other ear. The UK National Deaf Children's Society notes the wireless link is often Bluetooth.
In a CROS system the unit on one side is not delivering sound into its own ear at all. It sends what it picks up to the ear on the opposite side. For more on remote microphones as a separate topic, see what a remote microphone is for hearing aids.
What BiCROS Adds
BiCROS uses the same pickup-and-send arrangement, with one difference on the receiving side. The device on the other ear is a working hearing aid, so it amplifies sound for that ear as well as playing in the sound sent across. RNID describes the BiCROS version as capturing sound from both sides, with the hearing aid on the ear with better hearing amplifying it.
The difference in one line:
- CROS: the device on the hearing ear delivers the sound picked up on the other side, for a person with good hearing in that ear.
- BiCROS: the receiving ear's device passes on that signal and also amplifies sound for its own ear.
Which of the two a system is set up as comes down to the arrangement of the receiving device, which is a matter for the person who programs it.
Who These Systems Are Described For
Charity information describes CROS systems as designed for people who hear in only one ear, and BiCROS as designed for people whose better ear also has some hearing loss. The National Deaf Children's Society uses the terms "unilateral or asymmetrical" for this kind of hearing. These are descriptions of how the devices are designed, not a way of working out what kind of hearing a person has. That is a question for a hearing assessment. RNID and the National Deaf Children's Society are UK charities.
The same charity notes these systems are generally not used with babies and young children, and are usually considered only for older children and teenagers. Product information for the specific model sets out its own details.
What the System Does Not Do
Because sound is routed across, a CROS or BiCROS system does not recreate two-sided listening in the way two separate hearing aids do. RNID points out that sound localisation, working out where a sound comes from, may still be difficult.
CROS, BiCROS and Other Options
CROS and BiCROS are one approach among several for one-sided hearing, and other devices exist that work in different ways. Our article on hearing aids vs cochlear implants looks at another comparison, and the role of the telecoil in modern hearing aids and our page on assistive listening devices cover wider options for listening in different situations. A general overview of the device range is on the hearing aid solutions hub.
CROS and BiCROS and the Hearing Services Program
In April 2026 the Department of Health published Provider Notice 2026-02, which lists CROS and BiCROS devices on the approved device schedule alongside the fully subsidised hearing devices they are compatible with. Eligible clients' fully subsidised devices are paid for by the Australian Government, and conditions apply under the Australian Government Hearing Services Program.
A Quick Summary
- CROS and BiCROS systems pick up sound on one side and send it, usually wirelessly, to a device on the other ear.
- In CROS, the receiving device passes the signal on. In BiCROS, it also amplifies sound for its own ear.
- Sound localisation can still be difficult.
- Whether a system is relevant is a matter for a hearing assessment.
If you'd like to chat about your hearing, the friendly team at CQ Audiology in Rockhampton is here to help. You can read about hearing aids in Rockhampton, call (07) 4848 6528 or book online.
This article is general information, not personal medical advice. For advice about your own hearing, speak with your GP or a hearing care provider.
Sources: Australian Government Department of Health (Hearing Service Program Provider Notice 2026-02); RNID (CROS and BiCROS hearing aids, UK charity); National Deaf Children's Society (CROS and BiCROS hearing aids, UK charity).
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