Modern Solutions when you only have one working ear – CROS/BICROS

Time To Read: 5 minutes


This popular blog post from 2016 has been updated in October 2020.

Single-sided deafness requires special solutions, we take a look at CROS/BiCROS.

  • What is a Bi/CROS system
  • Potential benefits and limitations
  • Is it for me?

Single-sided deafness (SSD) refers to a condition where a person has usable hearing in one ear only. The poorer ear does not receive benefit from traditional hearing aids, whilst the better ear may have normal hearing, or a hearing loss.

People with SSD may have difficulties in picking up on the direction of sounds (localisation), detecting speech on their poorer hearing side, and difficulties hearing in the presence of background noise. Fortunately there are modern solutions to help these patients. One such solution is the CROS (Contralateral Routing of Signal)/BiCROS (Bilateral Contralateral Routing of Signal) system.

Figure 1. CROS system (Image -

What is a Bi/CROS system?

A CROS system is worn when the individual has one ear with unaidable hearing, and one ear with normal hearing. A microphone, worn on the bad ear, picks up the signal and transmits it to a receiver worn on the ear with normal hearing.

A BiCROS system is worn when the individual has one ear with unaidable hearing (where a hearing aid won't work), and the other ear has a hearing loss. A microphone, worn on the bad ear, picks up the signal and transmits it to a hearing aid worn on the better hearing ear. The hearing aid then amplifies the signal to a level that the user can hear.

Figure 2. BiCROS System (image -


Potential benefits and limitations

Successful CROS users will find several improvements to their daily communication difficulties. These include:

  • An improved ability to hear people when speaking to their poorer ear
  • An improved ability to hear in background noise (if speech is coming from the poorer side); and,
  • Better awareness of sounds in the environment.

Unlike other SSD solutions, the CROS/BiCROS is easily fit in the audiologist’s office and does not require any surgery. Since the CROS/BiCROS device does not amplify sound to the poorer ear, it is unlikely that users will experience a significant improvement in ability to localise sounds.

However, some clients do report subjective improvements in localisation ability.

Examples where Cros/BiCros is of benefit are:

  • In a car when your poor ear is towards the driver or passenger
  • In groups, where people are located on your poorer ear's side
  • Walking in traffic, where someone is speaking to you from your poorer side.
  • At home, when you aren't facing the speaker and they start speaking from your deaf side.

So gone are the days, where you had to make sure you have people sitting on your "good" side. 

It is important to note that this system will not reduce tinnitus in your bad ear as there is no direct stimulation to the poorer hearing ear. 

NOTE: Wireless CROS/BiCROS systems use a lot of battery power, so hearing aid battery life might only be a few days, although some manufacturers do offer some better battery saving technology, or auto power saving modes. Some manufacturers also offer rechargeable models, which addresses this issue very effectively, giving up to 14 hours of  use before a charge is required.  

What are the differences between current CROS options?

There are several manufacturers that currently offer a CROS solution,  and each company utilises their own technologies; however, the end-goal is the same: to enable the wearer to hear sounds coming from their poorer ear in their better hearing ear.

The manufacturers that currently offer wireless CROS solutions are: Phonak, Starkey, Widex, Signia (Siemens), and Oticon. Let’s take a quick look at some of the differences in CROS technology between these manufacturers.

Phonak: For a long time, Phonak dominated the CROS market, as there just weren’t any other discreet, wireless CROS options available. Their current iteration is the CROS B, part of the Belong family, which is 2 generations behind their most recently-released Paradies platform. However, it is rumoured that CROS will  join the Paradise family, likely sometime in 2021. CROS B is the most versatile CROS on the market as it’s available in RIC (including a lithium-ion rechargeable option), BTE, ITC, and ITE styles. As it’s on an older platform, CROS B doesn’t offer any  direct streaming compatibility, although you can get streaming to the hearing aid via an accessory. Of all the CROS options on the market, it is one of the most power hungry, so expect to change batteries every 2-5 days, depending on battery size. A rechargeable CROS will offer up to 14 hours of continuous use on a full charge. CROS B is available in all technology levels in the Belong platform, and compatible with all wireless hearing aids except Audeo B-Direct.

Oticon: Oticon CROS is available in one style only (same design as the mRITE-T), but compatible with all hearing aids (except the Opn S 3) in their latest Velox S platform (Opn S, XCeed, and Ruby). It offers direct streaming to the hearing aid (iPhone only), and NFMI for the CROS transmission (Oticon calls this TwinLink technology). This means that you can stream audio from a device to your hearing aid but still maintain the CROS transmission. In fact, research has  revealed a 50% improvement in speech awareness for those who had CROS transmission on when streaming. 

Starkey: Like Oticon, Starkey offers direct streaming to iPhone and select Android Smartphones while maintaining the CROS transmission. Their CROS offers a battery saving function that features an auto shut-down for the CROS if it’s out of range of the hearing aid for more than 30 minutes. Starkey CROS is compatible with the latest Livio, Livio AI, and Livio Edge AI range (all technology except 1000 level). It’s available in a RIC 312, RIC R, and BTE 13 CROS styles. Expect about 14 hours of wear time with the lithium-ion rechargeable CROS RIC R. For those who wear their hearing aid and CROS for longer than 14 hours a day, there is also a turbo charger available. For Starkey Bi/CROS fittings, you need to match the battery type of the hearing aid and CROS for them to be compatible, so you wear 2 devices that look the same. 

Signia: Signia has 3 CROS options on their latest X platform, and, like Starkey, match the CROC style to the hearing aid style - Pure Charge&Go X (lithium-ion rechargeable RIC), Pure 312 X (RIC), and Silk X (instant fit CIC style). CROS Pure Charge&Go X offers up to 21 hours of use on a full charge. The Pure hearing aid options offer direct streaming via iPhone (while maintaining CROS transmission), and also feature motion sensors. All 3 CROS options use binaural link between the hearing aid and CROS to provide binaural processing, which can greatly improve spatial awareness. CROS Silk X also uses the binaural link to take advantage of Signia’s narrow directionality feature - an industry-first for a CROS device. 

Widex: Probably the best battery saving technology on the market currently, using up to 3 times less battery power compared to some other CROS options. Widex CROS is available in RIC or BTE styles only, but is compatible for transmission with a range of RIC (including the discreet Passion, but excludes Fusion 2), BTE and custom hearing aids (including a CIC) in the Evoke platform, which is one generation behind their latest Moment platform. There is no direct streaming available, although streaming to the hearing aids can be achieved using accessories; however, CROS transmission is turned off while streaming. 

Is it for me?

Modern CROS/BiCROS devices are suitable for most people with SSD. Potential candidates will have one ear which cannot be aided by traditional hearing aids, and one ear which has good speech understanding at either normal, or elevated volumes. The better hearing ear may have normal hearing, or a hearing loss. It is suitable for those who want to hear more clearly when people are speaking to their poorer ear, and for those who do not wish to have surgery. Another advantage of the CROS is that it is normally much cheaper to get an aid and a CROS than two hearing aids.

With so many options available, the best way to see whether you are a candidate for CROS/BiCROS, and which option best suits your needs, book an appointment for a hearing and speech in noise test and to discuss this option further with one of our specialist audiologists

Further reading:

How To Manage Single-sided Deafness

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