Audio Engineering Society Singapore Section

On Friday, 27 March 1998 at about 7.45pm, members and guests of the AES Singapore Section gathered at the Ngee Ann Polytechnic campus located at Clementi Road for a talk by Mr. Christopher Yap, Research Engineer from the Centre for Signal Processing (CSP) at Nanyang Technological University. Christopher is also Treasurer to the AES Singapore Section and has been involved in the live-sound reinforcement industry since 1989 before joining CSP. 

Christopher gave an interesting 1-hour presentation on the DSP implementation of audio effects to a packed audience of 7 members and 32 guests that comprised of audio engineers & research scientists from the industries as well as academics & tertiary students from the local universities and polytechnics. 

With the onset of digital audio signal processing, many of these effects have since been "digitized" and implemented by program code that runs on Digital Signal Processors (DSP). These have brought real-time audio effects to the PC - a relatively new and interesting idea to the home computer users.

The audience was later introduced to a low cost, high-end PC add-on sound card based on the ADSP 2181 fixed-point DSP and AD 1816 SoundPortTM Controller ICs that incorporates the SounDSPhinx Digital Audio Effect software modules developed by Christopher. Because of its expandability and flexibility, a wide range of audio processing algorithms can be implemented that range from 3D spatialization to digital modulation effects. Popular audio processing such as chorusing, flanging, room spatialisation and graphic equalization are among the functions offered. The approach of using DSP allows sound card manufacturers to differentiate their products from the rest in the market in terms of cost and function besides the sound effect processing capabilities.

Sensory Station Plus

This user-friendly digital audio effect software is also incorporated into another product known as the SENSORY STATION PLUS - a full-duplex intelligent microphone that can be connected to a PC for audio conferencing application. This product, which generated much interest at the Comdex Fall '97 trade show held in Las Vegas USA, introduces an innovative new concept of multimedia signal processing products in the PC market. Developed by a homegrown company known as BITwave Pte Ltd, this gadget also enhances the audio output quality of your PC's sound card besides its many advantages.

The software incorporates many interesting audio processing modules. Firstly, never before seen on a PC platform, a stereo 20-band digital graphic equalizer with octave band centre frequencies and ±12db gain/attenuation. Complementing the popularity of surround sound these days, is a 4-channel surround sound algorithm that converts a 2-channel stereo input to a Left-Right-Centre-Surround 4-channel configuration. On top of the already amazing features, home musicians can definitely benefit substantially from the digital delay modulator, which is capable of effects such as digital delay, flanging, chorusing, pitch bending and metalization. A digital spatializer that can simulate a few different sized rooms is also included. In addition, in every module is a 3D-spatialiser control which serves to spread the sound beyond the physical limits of your speakers. 

SENSORY STATION PLUS intelligent microphone developed by BITwave Pte Ltd with the digital audio effect software modules developed by Mr. Christopher Yap that is incorporated into the gadget". 

The background and basics of the theory behind the audio effects such as echo, flanging, chorus, metalization, reverberation and some novel sound effects were introduced. These were accompanied by a presentation of the basic DSP algorithms that were used to implement the effects. An algorithm for implementing a digital graphic equalizer that is based on the 2nd-order IIR (Infinite Impulse Response) digital filter structure was also presented. A real-time sound demonstration using the SENSORY STATION PLUS summed up the talk for the evening. 
 

Copyright 1999 AES Singapore Section