Contralateral Routing of Signal (CROS) and BiCROS systems are specialized hearing technologies designed to address single-sided deafness (SSD) or highly asymmetrical hearing loss. SSD occurs when one ear has little to no usable hearing, while the other ear retains normal function, making a traditional hearing aid ineffective for the impaired side. The CROS system captures sound on the unaidable side and wirelessly transmits it across the head to the better-hearing ear. BiCROS technology is a variation used when the better ear also requires amplification, combining sound routing with traditional amplification capabilities. This technology restores environmental awareness and sound access lost due to profound hearing loss in one ear.
Understanding How CROS Technology Works
The core function of a CROS system is to eliminate the acoustic barrier created by the head, known as the “head shadow effect.” This effect causes a reduction in the intensity of high-frequency sounds originating from the deaf side, making speech understanding difficult. A dedicated microphone and transmitter unit is worn on the ear with non-usable hearing, picking up sound waves from that side of the environment. This captured acoustic energy is converted into an electrical signal and transmitted wirelessly to a receiver unit worn on the functioning ear. Transmission often utilizes advanced wireless protocols, such as the 2.4 GHz range or near-field magnetic induction (NFMi), to ensure a clear, interference-free signal.
Key Features Defining Superior CROS Performance
Superior CROS performance relies on advanced digital signal processing to manage complex sound environments. High-end systems incorporate adaptive noise reduction algorithms tailored to maintain speech clarity while minimizing background noise transmission from the unaidable side. Advanced directionality is also a significant factor, utilizing multiple microphones to focus on speech signals originating from the deaf side and improving the signal-to-noise ratio.
Wireless connectivity standards define how the user interacts with media and communication devices. Modern CROS systems offer robust Bluetooth capabilities, such as Bluetooth 5.3, allowing direct streaming of phone calls and media from both iPhone and Android devices to the receiving hearing aid.
The power source impacts user convenience, with many leading models offering rechargeable lithium-ion batteries that provide reliable all-day performance, often exceeding 16 hours on a single charge. Finally, physical design matters, as some manufacturers offer discreet, custom-fit, completely-in-canal transmitter options for cosmetic appeal.
Comparing Leading CROS Systems
The market for CROS and BiCROS technology is led by several major manufacturers, each offering unique strengths based on their core hearing aid platforms.
Phonak offers the CROS Infinio, highly regarded for its advanced AutoSense OS technology and robust Bluetooth connectivity, including future compatibility with Bluetooth LE Audio. Clinical studies suggest that Phonak BiCROS users experience better speech recognition in noise compared to older models.
Oticon’s CROS Px system is notable for its deep neural network processing, trained on millions of sound samples to offer superior speech and noise separation. This system also provides extensive backward compatibility, allowing the CROS transmitter to pair with a wide range of older Oticon hearing aids.
For users prioritizing discretion, Signia offers the CROS Silk Charge&GO IX, a completely-in-canal rechargeable transmitter that is among the smallest options available. Starkey’s Edge AI RIC RT CROS integrates artificial intelligence and a deep neural network, giving users access to features like Edge Mode Plus for on-demand sound optimization. Manufacturers like ReSound focus on natural sound perception using their M&RIE (Microphone & Receiver-In-Ear) technology, often providing superior streaming quality with a longer wireless range.
The Path to Getting Fitted
The journey to acquiring a CROS system begins with a comprehensive hearing assessment conducted by a licensed audiologist. This evaluation determines the specific nature of the hearing loss to confirm suitability for CROS or BiCROS technology.
The fitting and programming of CROS devices are highly specialized and require objective verification for optimal performance. A crucial step is Real Ear Measurement (REM), which uses a probe microphone to verify that the sound transmitted successfully overcomes the head shadow effect. Accurate measurement is necessary to correctly program the system for maximum benefit.
Once programmed, most clinics offer a trial period, allowing the user to experience the device before committing to the purchase. While costs vary, CROS systems are generally priced lower than surgical alternatives, and financing options, including healthcare credit or Health Savings Account (HSA) use, are often available.