What is a CROS Hearing aid, and How Does It Work?

October 12, 2022
Amy Sarow | Doctor of Audiology
Written by
Amy Sarow | Doctor of Audiology
Soundly Staff
Reviewed by
Soundly Staff
Man wearing CROS hearing aid from Oticon

CROS Technology for Those With Single-Sided Hearing Loss

Do you have good hearing in one ear and a lot of hearing difficulty in the other ear? Certain types of hearing devices are specifically designed to help those with single-sided deafness (SSD).

Read on to learn more about CROS hearing aids.


Not everyone has hearing loss in both ears. Sometimes hearing loss affects only one ear.

Several different etiologies can cause a sudden hearing loss, for example, a benign tumor on the hearing nerve (vestibular schwannoma), viral infection, or Meniere's disease

Single-sided deafness (SSD) comes with particular specific challenges. One ear hears normally, while the other ear has significant hearing loss. In quiet situations, understanding isn't a problem. However, a number of other situations can make it difficult to understand. For example, when someone speaks to your bad ear and there is noise coming to the good ear.

The car is one place where single sided hearing loss is noticeable. When you're the driver, it will be hard to converse with the passenger if your good ear is facing the road noise by the window. The same is true in social situations when the speaker is located on the bad-ear side. 

This can be even more challenging for those with some hearing loss in the good ear.

Adding in any level of background noise can really change how much of the conversation comes through, understandably. 

Additionally, when the hearing loss in the worse ear is significant enough, speech understanding is often quite low with traditional hearing aids. In this situation, putting a conventional hearing aid on an ear with substantial hearing loss and a lack of speech clarity will likely not be helpful.

In these cases, a CROS hearing aid system is recommended. CROS devices route the sound from one side of the head to the good ear. Let's take a closer look at a CROS hearing aid and how it works.

CROS Hearing Aid: What It Is and How It Works

CROS stands for 'contralateral routing of off-side signal', and a CROS hearing aid system is made up of two devices: 1) traditional hearing aid and 2) a microphone. On the outside, it looks like two hearing aids. The device with the microphone is worn on the ear in the same way as a traditional hearing aid. 

A CROS hearing aid is a device with a microphone that picks up sound coming to the 'bad ear' and sends it to a hearing aid on the good ear.

Think of it this way: the bad ear cannot understand speech, so instead, it gets sent to the better ear that can easily understand it. The microphone picks up when someone speaks towards the bad ear, making it much easier to understand.

Who will benefit from a CROS?

If you have SSD, a CROS can be very helpful in situations where your conversation partner is positioned towards your bad ear. It will do a good job of sending the sound over to your better ear in this scenario. However, in situations where the microphone is picking up noise and sending it to the good ear, that will likely not be useful and can even make it harder to understand. Therefore, a CROS hearing system will work best for those with SSD in specific situations. 

Those with SSD can also evaluate surgical interventions, such as cochlear implantation or bone-anchored hearing aids. However, a non-surgical trial of a CROS option is advisable first for two reasons. 1) Insurance will often advise or require a hearing aid trial before proceeding with surgery. 2) Additionally, some people find sufficient benefit from hearing aids and choose not to pursue surgical options. 

What are BiCROS Hearing Aids? 

A BiCROS device is just another configuration of a CROS that gives the better ear some added volume. This device is programmed for someone with some hearing loss in their better ear while still sending all of the sounds from the poorer ear over to the better ear. A person with mild or greater hearing loss in their better ear will benefit from a volume boost based on their hearing prescription, in addition to having the sound from the poorer ear sent over to the better ear.

Should You Wear One Hearing Aid or Two?

If you hear better in one ear than the other, it's worth considering whether one or two hearing aids will work best. Generally speaking, we hear best with two ears, and most people with hearing loss have it in both ears. The one exception is if one ear has sufficient hearing loss to the point that speech is distorting understanding and causing interference with the brain's ability to understand speech in the better ear. 

The good news is that there is a trial period when you purchase hearing aids. If you haven't tried two hearing aids before, it makes a lot of sense to try two. See how you do with two hearing aids. Some people find the environmental awareness they get from wearing two hearing aids can be beneficial. Others find that they don't perceive enough benefit and wish to only keep one hearing aid. If you don't try this, you can't know. 

If you try two hearing aids and find that just one hearing aid works best for you, a CROS hearing aid is still an option. For your hearing aid trial, you'll want to select one of the hearing aid brands that has a CROS option (see the list below).

Do yourself a favor and try wearing two hearing aids. Remember you have the trial period to find out if your bad ear is getting enough benefit. The one exception to this is if your bad ear has no hearing, in which case a CROS will be the best option.

Leading CROS Brands and Products 

Phonak CROS

Phonak is one of the top hearing aid manufacturers and a leader in CROS technology as well. Phonak makes a CROS hearing aid with a variety of useful features. The CROS device and compatible hearing aid works with the Phonak Paradise platform and come in several different levels of technology. This device comes in both rechargeable and size 13 battery options. 

The Phonak Audeo Paradise hearing aid is compatible with Phonak CROS in rechargeable and battery-powered options. This device also works with the myPhonak app and is compatible with iPhone as well as Android. 


  • For Android users, Phonak is a great option. Bluetooth Classic allows for more options for device connectivity.
  • The Phonak rechargeable case has a compartment for a drying capsule and works well for active individuals. 


  • Notifications cannot be disabled when Bluetooth is connected to the phone.
  • If dexterity is a concern, it can be difficult to remove the hearing aids from the charger.
  • For the battery option, size 13 will be a larger size than 312.

Oticon CROS 

The Oticon CROS PX is available to work together with the Oticon More and will also have forwards and backward compatiblility with other Oticon hearing aid models. The CROS is available in rechargeable and battery (size 312) options.

The Oticon ON app works well with iPhone as well as some Android models.


  • For iPhone users, Oticon is a great option.
  • The Oticon rechargeable case is easy to work with for all levels of dexterity. 
  • The rechargeable battery is able to be replaced in the office and doesn't need to be sent in if the battery needs to be replaced.
  • The battery option uses a size 312, which means a device with a smaller profile.
  • The app offers a "Find My Hearing Aid" feature in the app.


  • The simplicity of the app does not allow for making a lot of adjustments or changes.
  • Oticon uses the ASHA protocol to connect to a phone, which can make connectivity less stable.

Signia CROS X

The Signia CROS X works together with the Signia Pure. The CROS is available in both rechargeable and battery options (size 312). The Signia app works with both iPhone and Android.


  • Convenient charging case.
  • The 'mask mode' on the app can be very useful to ease understanding.
  • Additional features on the app can be adjusted, such as microphone directionality.


  • Lower levels of technology will need to use the app in order to adjust the volume or other settings (rather than the button). 


For those with SSD, a CROS hearing aid can be a great option to help in situations when the speaker is located on the poorer ear side. Use your hearing aid trial period to your advantage to find what works best for your situation.

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–The Soundly team

Frequently asked questions

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