Dynamic range compressor and spatial audio application

• Main Author: Shen, Shuo.
• Other Authors: Gan Woon Seng
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Electrical and electronic engineering
• Online Access: http://hdl.handle.net/10356/54575
• Institution: Nanyang Technological University

Dynamic Range Compression is one of the most useful and most widely used audio effects in broadcasting, DVD or car CD player setting. It is crucial when audio is recorded and played using different devices. Without proper audio gain control, a radio receiver or speaker would vary to an extreme extent, causing problem like clipping, overflow or underflow. Dynamic Range Compression also can be used in speech recording. Because of the presence of noise from the surrounding area, the signal-to-noise ratio (SNR) may not be high enough to have an acceptable quality. By increasing the volume of the human voice, recording using Dynamic Range Compression will raise the signal-to-noise ratio to produce a clearer version. However, there is little understanding and analysis of compressor design technique. Surround sound is a technique to produce the sound with additional audio channel from the speakers to give the listener 360o sound source direction. It is widely used in cinemas and becoming more popular in consumer market like home theater. Traditional surround sound system is achieved by using multiply discrete audio channels surrounding the listener. In this project, the surround sound effect, also known as the 3D sound effect, is achieved by using Head-Related Transfer Function with only two audio channels. This is more suitable for portable devices like laptops, tablets and smartphones. Since a lot of people are watching videos and movies on the portable devices while travelling, they would like to enjoy the surround sound effect just like they are in a cinema or home theater. Imagine you are playing the latest first person shooter game with your friends. There are so many types of sounds, such as radio, footsteps, explosion and gun sound effect. If the sound effect volume is too low, the enemies’ footsteps sound cannot be heard while ambushing. However if the sound effect volume is too high, the explosion sound while fighting would be too high to bear with. Dynamic Range Compressioncan be used to reduce the volume when there is loud explosion sound, while maintain or increase the volume of footsteps while in quiet environment. 3D surrounding sound effect is a must for the optimal game experience. It helps to determine enemies’ positions through the direction of gun sound. That is why Dynamic Range Compression and 3D sound effect is integrated together in my project. The background section of this report talks about the relevant theories including digital signal processing, dynamic range compression, head-related impulse function and finite impulse response filters, also the hardware used and references. The project section presents the design, the implementation, the results and the problems solved. The conclusion section discusses the work accomplished and what could be done in the future.