Some of our products employ the novel 16 channel critical band spaced digital filter bank design  with natural hearing response proposed by Prof Bah Hwee Gwee and Prof Joseph Sylvester Chang from School of Electrical & Electronic Engineering, Nanyang Technological University, Singapore. Prof Gwee and Prof Chang are digital hearing instrument experts which have a number of inventions, including  US granted patents on circuit design. These include the low-distortion (<THD+N: – 78dB) digital filter bank, low power ([email protected]) Class-D amplifier  and digital signal processor  circuits for digital hearing instruments. They have been IEEE Distinguished Lecturers for IEEE Circuits and Systems Society.
 K.S. Chong, B.H. Gwee and J.S. Chang, “A 16-Channel Low Power Non-Uniform Spaced Filter Bank Core for Digital Hearing Aids,” IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 53, no. 9, pp. 853-857, 2006.
Figure 1: Block diagram of the critical band spacing spaced 16-channel filter bank
Figure 2: The magnitude response of the critical band spaced 16-channel filter bank
 B.H. Gwee, J.S. Chang and V. Adrian, “A Micropower Low Distortion Digital Class D Amplifier based on an Algorithmic Pulse Width Modulator,” IEEE Transactions on Circuits and Systems I: Regular Paper, vol.52, no. 10, pp. 2007-2022, Oct 2005
Figure 3: Detailed illustration of the LI single-sided trailing-edge PWM sampling
Figure 4: Block diagram of the Linear Interpolation Pulse Width Modulator for Digital Class-D amplifier with THD » 0.03%, fold-back distortion = –98.4 dB
Figure 5: Microphotograph of the Class D output stage
 Y. Shi, B.H Gwee and J. Chang, “Asynchronous DSP for Low-power Energy-efficient Embedded Systems,” Microprocessors and Microsystems, v35, n1, pp. 318–328, 13 Feb 2011.
Figure 6: Block diagram of the Asynchronous Low-power (54.5 uW/[email protected] V) Digital Signal Processor for Digital Hearing Instrument
Figure 7: Area breakdown of the Asynchronous Low-power Digital Signal Processor