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Practical Implementation of Radial Filters for Ambisonic Recordings

Publication ID 22199
Abstract Ambisonics is the representation of an incident sound held by a sum of angular modes (spherical harmonics) up to a given order. Recording and playback of natural sound helds is achieved by using compact spherical microphone arrays and a surrounding spherical loudspeaker array. Typically, the radius of the microphone array is much smaller than the radius of the loudspeaker array for playback. Thus, the recording requires an accurate adaptation to the radius of the playback facility. This is achieved by radial lters compensating for the radial propagation of the modal components. Such ideal radial lters exhibit very high gains at low frequencies, especially for higher order components. However, the feasible dynamic range for ltering is limited, mainly by the signal-to-noise ratio of the microphone array. Usually, the dynamic range of the ideal radial lters is limited by applying high-pass lters with adequate cut-o frequencies. Regarding the low frequency range, this high-pass ltering causes losses in terms of amplitude and power, respectively. We present a new approach that accounts for these losses. Whenever higher order components are omitted, the remaining lower order components are amplfied accordingly. This is achieved by an appropriate lter bank, applied in the modal domain.
Edition title Proc. of the International Conference on Spatial Audio 2011 (Proc. of the International Conference on Spatial Audio 2011)
Publisher Month 02
Publisher Name Malte Kob
Publisher Location Hochschule für Musik, Detmold (Deutschland)
Note procedure: without peer reviewing
Status published
Publication Type full paper
Publication Reference proceeding
Year of Publication 2011
Authors Baumgartner, R., Pomberger, H., Frank, M.
Editors Kob, M.