Consulting Services

Our chief technical officer, Jim Hendrix, is available for consulting assignments. Jim holds a masters degree in Physics and is now retired from The National Center for Physical Acoustics where he developed numerous prototype communication devices for the NEDU in Panama City. Jim has extensive experience developing state-of-the-art solutions for deep diving communications problems and testing speech intelligibility by standard methods. His experience includes both passive and active (DSP) control of helmet noise. In 2001, Jim developed the first helium unscrambler with noise reduction capabilities (below), a design that set the standard for the next 10 years. Contact us with your questions.

In-House:

$90 / hr

On-Site:

$180 / hr

Travel:

$18 / hr

Expenses:

Actual

Helium-Speech Unscrambler Developed for US Navy

In 2001, Oxford Signal Processing developed and delivered to the U. S. Naval Experimental Diving Unit (NEDU) 43 copies of their fourth generation helium-speech unscrambler. Each consisted of three circuit boards that replaced corresponding boards in their existing Tethered Diver Communication System. This unscrambler has the following features:

• Dual, 60 MHz, 32 bit, floating-point Digital Signal Processors
• Dual high-speed SRAM memories for program execution
• Dual port SRAM memory for inter-processor communication
• FLASH memory for program storage
• 5-times over-sampling for good high-frequency performance
• Frequency-domain or time-domain domain algorithms
• Noise reduction filter (toggle levels 1, 2, 3, bypass)
• Expansion ratio variable to any depth!
• Treble boost for input signal
• Field upgradable firmware
• Unscrambler bypass switch

Other Saturation Diving Projects

• Waterproof microphone for saturation diving helmet.
• Procedure for testing microphones for use in saturation-diving helmet.
• Passive noise reduction ear phones for saturation divers.
• Active noise reduction (ANR) headset for saturation divers.
• Procedure for measuring the Articulation Index and Speech Intelligibility Index, with Modified Rhyme Test (MRT) stimulus, to predict the intelligibility of speech presented to saturation divers.
• Consulted with a major manufacturer to incorporate the Navy unscrambler into a commercial diving intercom.

Other Projects

• Prototype ANR ear plugs for use under ear muffs in ultra-high noise environments.
• Analog interface circuit card for use with Texas Instruments TMS320C30 digital signal processor.
• Integrated interface circuit card for use with Texas Instruments TMS320C40 digital signal processor.
• Digital signal processing run-time library. Control and debugging routines for use with Texas Instruments TMS320C30 and C40 processors.
• Digital amplifier. Delay adjustable with greater resolution than sample period.
• Diagnostic, wireless telecommunications receivers for testing Motorola FLEX 4-channel two-way paging system.
• Smart acoustically active surfaces. DSP controlled surfaces that detect sound in water and cancel both reflected and transmitted waves simultaneously.
• Predictive, feedback-control algorithm for reducing sound or vibration.
• Generalized feedback controller. Listens to noise spectrum, probes for the feedback transfer-function, calculates and implements optimal IIR filter for noise or vibration reduction.
• Prototype ANR stethoscope for use in medical evacuation helicopters.
• ANR stethoscope with self-audiogram and hearing correction for doctors with hearing impairments.
• Improved conventional electronic stethoscope.
• 32-channel, active noise controlled acoustical event detector for non-invasive inspection of fruit for larva infestations by counting chewing events.