The hardware-design group at India's government-funded CDAC (Center for Development of Advanced Computing), in Thiruvananthapuram has developed a low-cost DPHA (digital programmable hearing aid) that a user wears on his body. The DPHA-1 device employs a proprietary ASIC and embedded DSP to deliver stable amplification characteristics over a wide dynamic range.
Unlike conventional analog hearing aids, you can tailor DPHAs to improve clarity of speech, reduce background noise, and help control unwanted loudness. You can also program them to make automatic adjustments in a variety of settings. "Currently, no other manufacturer in India offers a DPHA in the body-worn format," says project head R. Ravindra Kumar, additional director at CDAC. "They are available only in the more expensive, behind-the-ear format. Our design has all the advantages of DPHAs, such as reprogrammability, stability, and fidelity, but at a lower cost of ownership. This has great benefit for a country like India, which has a huge hearing-deprived populace [about 30 million people] for whom affordability is a significant issue. Also, bodyworn DPHAs are more convenient for children."
CDAC's DPHA-1 features a digital volume control to eliminate the crackling-noise characteristic of conventional hearing aids and incorporates frequency-dependent filtering to match its output to the audiogram of the user. You can reprogram the device in the field with PC-based software to tailor the output to match the user's hearing characteristics over a period of time. "All this is made available in a low-power package using CMOS-ASIC implementation," says Kumar. The device works on an easily available, rechargeable lithium-ion battery.
Biju C. Oommen, joint director and deputy head at CDAC, says that the DPHA-1 is a multidisciplinary effort that melds diverse electronicdesign technologies, such as DSP design, algorithms and firmware, ASIC- and analogcircuit design, and power management, with the physics of audiology, the anatomy of the human ear, and precision mechanical fabrication. "We needed to develop the algorithms for the programmable filters and balance the implementation of hardware/software functions in a 32-bit, realtime embedded system using our RISC core," explains lead designer N. M. Shaji. The pc-board design and engineering were other challenges because the designers had to cram all the components into a 4030- mm pc board. They also had to carefully design the enclosure to prevent internal mechanical resonance and microphone feedback.
Currently, the DPHA-1 is undergoing formal field trials after CDAC deemed prototype field trials using FPGA implementation successful. CDAC is considering fabricating a 1 million-gate SOC (system-onchip) ASIC and is scouting for manufacturing partners. The organization estimates that it could eventually offer the DPHA to users for less than $20. "Our DPHA meets and exceeds the ANSI S3.22 and IEC 60118 standards. We will initiate the certification process after completion of clinical trials," says Kumar.
Winner of EDN Asia's Innovation of the Year award in 1999 for the Oorja ASIC, Kumar and his 30-strong engineering team have a number of successful projects, including energy meters, complex nuclear instruments, compact onboard computers for space vehicles, and smartcard monitoring and control systems, to their credit.
- Chitra Giridhar EDN Asia Center for Development of Advanced Computing www.cdactvm.in
The hardware-design group at India's government-funded CDAC (Center for Development of Advanced Computing), in Thiruvananthapuram has developed a low-cost DPHA (digital programmable hearing aid) that a user wears on his body. The DPHA-1 device employs a proprietary ASIC and embedded DSP to deliver stable amplification characteristics over a wide dynamic range. 
