Hear-Through Headset

The RTH Hawk hear-through headset is a double hearing protection system, comprising earmuffs and wireless communications earplugs, for use in high noise environments that protect the user from damaging ambient acoustic noise, while providing a hear-through function to restore situational awareness. The hear-through function is always enabled; however, the user may amplify or attenuate the volume of the ambient environment as needed. The communications earplugs are battery-free, require no charging and incorporate RTH wireless technology linked to the headset. The system is designed to be retrofit into headgear that incorporate a commonly used standard headband.

The Hawk system comprises multiple new technologies that were developed during NAVAIR SBIR government contracts including: ear simulators, hear-through systems, wireless battery-free and custom earplugs. The Hawk system also incorporates superior DSP audio processing and a proprietary low-noise (25 dBA SPL) high dynamic range (130 dB SPL) microphone design.

Limited production units were tested generally to the Performance Specification For Flight Deck Cranial (PMA202-08000/R-3) military specification. The tests are broken down into four main categories: 1)  hearing protection using real ear attenuation at threshold (REAT), 2) localization testing, 3) comfort study, 4) EMI/ESD testing and 5) other environmental testing. The test results were positive other than a couple of minor issues that can be corrected in the next production run. Test results are available upon request.

                                              Hawk retrofit system.

The Hawk system  is intuitive and easy to control. It is turned on and off by pressing both control buttons on the earcup, simultaneously. Pressing the right button increases the volume while pressing the left button decreases the volume. A beep indicates a volume change.

The Hawk system employs RTH PaRCN technology. PaRCN stands for "passive receiver communications nearfield" and refers to a magnetic nearfield induction wireless technology. A magnetic field transmitter in each earcup transmits the audio signal to each communications earplug in such a way that the earplug does not use a battery nor does it require charging. The wireless  earplug is sealed except for the sound delivery channel that provides a sound path through the earplug and eartip to the ear canal. According to RTH analysis, the wireless system meets IEEE standards and ICNIRP guidelines for safe human exposure to electromagnetic fields. This will be verified by a third-party testing facility.

Hawk retrofit headset installed in a K10 helmet with and without battery tray extended.

RTH wireless communications earplugs can be seen in the figure below.  The generic-fit earplug fits most users as well as both left and right ears. The semi-custom and full-custom earplugs are custom fit for an individual. RTH has the capability to manufacture all three types of earplugs. The generic-fit and semi-custom earplugs employ Comply Canal Tips manufactured by Hearing Components and are already used in the military. These come in slim, standard and large sizes. 

Generic-fit, semi-custom and full-custom RTH 

wireless earplugs.

The generic-fit earplug is worn in the ear as indicated below.  An unobtrusive leash (or tether) may be attached to the earplugs, if desired, using the earplug tether holes. Transmitters in the Hawk earcup communicate to the wireless earplugs creating a wireless link for communications and hear-through signals.

RTH wireless generic plug as worn in an ear.

The Hawk system has a unique (and patented) feature to aid in face-to-face communications. When the right control button is pressed and held,  the right cup ear simulator microphone is active, and the signal is sent to both earcups. In addition, the signal is limited to the speech band. In this way, improved face-to-face communications signal-to-noise levels can be achieved by the talker speaking into or toward the ear simulator of an earcup. The left cup is actuated in the same way.

The Hawk ear simulators (see below), are used to mimic the acoustic response of the human ear  in frequency response and directivity through the use of acoustic resonances and chambers. The microphones used in the ear simulators are protected from splashing water through the use of acoustic vents that prevent water passage but do not affect the acoustic response. The proprietary ear simulator microphones have an extremely wide dynamic range with a 25 dBA SPL noise floor and 130 dB SPL clipping level. For the user, this means that they will not hear noise due to the electronics and microphone and loud levels will be processed without clipping. RTH worked with a microphone manufacturer to design a special microphone for this product.

Hawk earcup with ear simulator.

The Hawk system audio processor ensures that the user is protected from any impulse noise (95 dB SPL peak) through special compression circuitry and protects the user from constant noise through automatic gain control. The automatic gain control limits exposure to 80 dBA SPL. At 120 dBA SPL ambient, the system will mute. 

The Hawk system uses two AA batteries, one in each earcup. The battery tray is opened by rotating the battery door at the bottom of each earcup, and a spring pushes the battery tray out. The batteries are held in the tray by tabs that will not allow the batteries to fall to the ground, to prevent a FOD hazard.  The battery door is easy to turn even when wearing gloves, and batteries can be quickly  changed in a matter of seconds while the headset is worn on the head. The batteries  provide between 20 and 40 hours of use when using NiMH rechargeable batteries. However, greater duration can be achieved using lithium or alkaline primary cells. The system beeps to warn the user when the battery level is low. 

The system is designed with a mini-USB connector on the digital signal processor circuit board. Software updates can be loaded onto the circuit board by the user without having to send the unit back to the manufacturer. It is possible to compensate the Hawk earcups for individual hearing requirements, such as compensating for hearing loss or other special needs.

An image of the RAC headset, manufactured by Gentex Corp. and sold internationally, can be seen below. It incorporates RTH wireless and hear-through technologies. Click on the image to expand or click here to see the full brochure.