Princeton University  

Research Projects and Emerging Audio Technologies

  1. Optimal Crosstalk Cancellation Filters
  2. BACCH™ Filters are optimized crosstalk cancellation (XTC) filters that allow 3D audio reproduction over a pair of loudspeakers. They yield maximum crosstalk cancellation level without introducing any spectral coloration to the input signal. BACCH™ Filters are at the heart of BACCH™ 3D Sound, Dynasonix, and other emerging technologies from the 3D3A Lab.

  3. Loudspeaker Directivity: An Ongoing Experimental Survey
  4. Loudspeaker directivity is the extent to which loudspeakers focus the sound in a particular direction (typically towards the listener) instead of broadcasting it in all directions around the room. Highly directive loudspeakers are ideal for 3D audio with crosstalk cancellation (XTC), since room reflections (which are weaker when using more directive loudspeakers) directly degrade the level of XTC. Consequently, the 3D3A Lab is conducting detailed measurements of the directivity of various loudspeakers using the lab's anechoic chamber. At present, the database contains the measured directivity data for twenty-six loudspeakers.

  5. Navigation of Higher-Order Ambisonics Recordings
  6. Traditional 3D audio recording techniques, such as binaural and ambisonics, enable a listener to experience a recorded soundfield from the vantage point of the recording device. However, employing one or more higher-order ambisonics microphones (such as the Eigenmike by mh acoustics) enables virtual navigation of the incident soundfield. The aims of this research project are 1) to identify and quantify fundamental and practical limitations of soundfield navigation and 2) to develop new techniques to overcome those limitations.

  7. Individualization of 3D Sound
  8. We perceive sound in three dimensions in everyday life. That is, without looking at a sound source, we can tell with reasonable precision, its location in space relative to us. We can do this because our brains process the sound signals that reach our eardrums in a manner that is unique to each of us. This should not be surprising as everyone's morphology is different (especially that of the outer ear), and this affects the sound reaching our eardrums in a highly idiosyncratic way. The processing that our brains do is tuned to our unique morphologies, and so swapping ears with someone else for instance would lead to a disorienting listening experience. To enable certain types of 3D sound reproduction systems, one of the tasks is to devise mathematical models that describe the effects our individual morphologies have on the sound we hear. The current project focuses on this task.

  9. Head-Related Transfer Function Measurements
  10. An individual's head-related transfer functions (HRTFs) describe the idiosyncratic filtering of incident sound waves by the individual's morphology. HRTFs are widely used to synthesize binaural signals for spatial audio reproduction, and are generally acquired either through acoustical measurements or by modeling from morphological data. Publicly available databases provide measured HRTFs for many human subjects and mannequins. However, few such databases also include corresponding morphological data. Consequently, the 3D3A Lab is measuring HRTFs and corresponding 3D morphological scans of subjects, which we provide as a freely available database.

  11. Binaural Rendering of Recorded 3D Soundfields
  12. Binaural recordings are inherently restricted in that they only possess accurate 3D localization cues for the recording individual. However, by using an array of microphones, such as the Eigenmike by mh acoustics, the incident soundfield can be extracted and the binaural signals that any given listener would hear from that point in the soundfield can then be computed numerically. It is the aim of this research project to develop tools and techniques to generate individualized binaural renderings of recorded 3D soundfields.

  13. The SOFA/AmbiX Binaural Rendering (SABRE) Toolkit
  14. The SOFA/ambiX binaural rendering (SABRE) toolkit is an open-source collection of MATLAB functions for generating custom ambisonics-to-binaural decoders for Matthias Kronlachner's ambiX binaural plug-in. The toolkit enables the user to generate custom configurations for the plug-in from any SOFA-formatted HRTFs or to add HRTFs to an existing ambisonics decoder. The toolkit is freely-available on GitHub.

  15. The Princeton Headphone Open Archive (PHOnA)
  16. The Princeton Headphone Open Archive (PHOnA) is a dataset of measured headphone transfer functions (HpTFs) from many different research institutions around the world. Visit this webpage to access the dataset.