title: Smoothing individual head-related transfer functions in the frequency and spatial domains.
abstract: When re-synthesizing individual head related transfer functions (HRTFs) with a microphone array, smoothing HRTFs spectrally and/or spatially prior to the computation of appropriate microphone filters may improve the synthesis accuracy. In this study, the limits of the associated HRTF modifications, until which no perceptual degradations occur, are explored. First, complex spectral smoothing of HRTFs into constant relative bandwidths was considered. As a prerequisite to complex smoothing, the HRTF phase spectra were substituted by linear phases, either for the whole frequency range or above a certain cut-off frequency only. The results indicate that a broadband phase linearization of HRTFs can be perceived for certain directions/subjects and that the thresholds can be predicted by a simple model. HRTF phase spectra can be linearized above 1 kHz without being detectable. After substituting the original phase by a linear phase above 5 kHz, HRTFs may be smoothed complexly into constant relative bandwidths of 1/5 octave, without introducing noticeable artifacts. Second, spatially smoother HRTF directivity patterns were obtained by levelling out spatial notches. It turned out that spatial notches do not have to be retained if they are less than 29 dB below the maximum level in the directivity pattern.
authors.affiliation: Jade Hochschule, Institut für Hörtechnik und Audiologie, Ofener Straβe 16-19, 26121 Oldenburg, Germany.
authors.forename: Eugen
authors.initials: E
authors.lastname: Rasumow
authors.affiliation: Jade Hochschule, Institut für Hörtechnik und Audiologie, Ofener Straβe 16-19, 26121 Oldenburg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Blau
authors.affiliation: Jade Hochschule, Institut für Hörtechnik und Audiologie, Ofener Straβe 16-19, 26121 Oldenburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Hansen
authors.affiliation: Universität Oldenburg, Department für Medizinische Physik und Akustik, Exzellenzcluster Hearing4All, Carl-von-Ossietzky-Straβe 11, 26129 Oldenburg, Germany.
authors.forename: Steven
authors.initials: S
authors.lastname: van de Par
authors.affiliation: Universität Oldenburg, Department für Medizinische Physik und Akustik, Exzellenzcluster Hearing4All, Carl-von-Ossietzky-Straβe 11, 26129 Oldenburg, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Doclo
authors.affiliation: Universität Oldenburg, Department für Medizinische Physik und Akustik, Exzellenzcluster Hearing4All, Carl-von-Ossietzky-Straβe 11, 26129 Oldenburg, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Mellert
authors.affiliation: Akustik Technologie Göttingen, Bunsenstraβe 9c, 37073 Göttingen, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Püschel