Meeting Topic: Spatial Audio
Moderator Name: Per Sjösten
Speaker Name: Ville Pulkki, Regional VP: Lennart Nilsson, Akustikmiljö: Aki Mäkivirta, Genelec
Meeting Location: Audiorama, Stockholm, Sweden.
The first speaker was Ville Pulkki, Regional VP. He gave a thorough overview of the Society's activities worldwide as well as focussing on the Northern Europe region.
Ville's main presentation was a fascinating walk through of the state of the art with respect to Spatial Audio. His Spatial Audio Research Group based at the Aalto University, Espoo, Finland is at the forefront of technology and processing for spatial audio. He described the idea of spatial audio as the ability to create the perception of one space when listening in another.
One of Ville's demonstrations used a graphical user interface to control sounds both in terms of direction and level . The 21 channel system installed in Audiorama was ideally suited to the presentation and an impressive effect was created using a combination of opera singers and marching soldiers. The Directional Audio Coding algorithm is an improvement over Ambisonics due to the fact that sound can be steered to individual channels and therefore the direction more precisely located in space — with Ambisonics a sound source is always split across at least 2 channels resulting in a wider image that is harder to pinpoint.
After the break, Lennart Nilsson gave a detailed description of the measures that were taken to create the perfect environment for spatial audio reproduction. In this kind of space it is important to create a balanced room decay. A substantial quantity of low frequency is incorporated into the architecture using novel solutions. The floor is built from a specially built slotted type construction covered with thick pile carpet. Benches along the sides of the room are designed to absorb low frequencies while acoustic plaster adorns the walls and ceiling. Care was taken not to create an anechoic environment which generally results in an unsettling sensation for people who are not accustomed to it.
Aki Mäkivirta, recently awarded a fellowship of the society, gave the third presentation which was on the subject of loudspeaker equalisation to compensate for room effects. He reinforced the principal that it is always the goal to acoustically design a listening space suited to the task before embarking on the task of loudspeaker equalisation.
Aki presented Genelec's approach to equalisation which involves a self-calibrating DSP algorithm used in conjunction with affordable measurement microphones. The automatic algorithm attempts to smooth the measured frequency response through attenuation of peaks rather than increasing the gain of dips.
Written By: Steven Liddle