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Frequently Asked Questions

What is HRTF ?
The spectral filtering of a sound source before it reaches the ear drum that is caused primarily by the outer ear is termed the head-related transfer function (HRTF). The binaural HRTF can be thought of as frequency-dependent amplitude and time-delay differences that result primarily from the complex shaping at human ears. One of todays popular applications of HRTF spectral shaping is fixed 3D-positioning of virtual (surround) loudspeakers for home stereo systems.
The pure directional parts of HRTF are also termed directional transfer functions (DTF).

What is Motion-HRTF ?
A moving source will cause dynamic changes for a fixed head. One cue for a moving source is Doppler shift, i.e. a source associated temporal change in pitch. Motion-HRTF use this principle in combination with other sound cues like location, ambience or distance cues for virtual motion. Motion-HRTF may be applied to single targets in a multi-source environment, e.g. for PC-games, but this is only one of many possible commercial applications.

What is Doppler shift ?
Doppler shift is commonly heard in nature as a pitch change when a speeding object passes a listener. When the object is approaching the listener, the pitch is higher than the resting pitch of the object. Similarly, when the object is retreating from the listener, the pitch is lower than the resting pitch.

What is ICA ?
"ICA" means blind separation of mixed signals aimed to achieve the output signals as independent as possible. One application area of ICA is audio separation e.g. for conversion of stereo into multi-channel sound.

What is Pseudo 5.1 Surround ?
"Pseudo 5.1 Surround" describes a technique that allows the derivation of 5.1 channels of sound from stereo recorded, two-channel source.

What is Pseudo-Stereophony ?
"Pseudo-stereophony" describes a technique that allows the derivation of two channels of sound from monaurally recorded, one-channel source.
A possible target application is e.g. internet radio.