Abstract: A method is dislcosed for stabilizing the apparent location of an audio signal having spatial components, in the presence of movement of emission sources designed to emit the audio signal while maintaining the apparent location, the method comprising the steps of (a) high pass filtering a signal proportional to the angular position of the emission sources; (b) utilizing the high pass filtered signal as an apparent angular position of the emission sources to determine an apparent location of the audio signal. Preferably, the high pass filtered signal is limited utilizing a non-linear asymptotically bounded function to limit the signal.

Abstract: An apparatus for implementing a Head Related Transfer Function on an input audio signal in a headtracked listening environment comprising: a series of principle component filters attached to the input audio signal and each outputting a predetermined simulated sound arrival; a series of delay elements each attached to a corresponding one of the principle component filters and delaying the output of the filter by a variable amount depending on a delay input so as to produce a filter delay output; a summation means interconnected to the series of delay elements and summing the filter delay outputs to produce an audio speaker output signal; headtrack parameter mapping unit having a current orientation signal input and interconnected to each of the series of delay elements so as to provided the delay inputs.

Abstract: A method of processing audio input signals comprising 1-bit, Sigma-Delta Modulated (SDM) signals is disclosed including the steps of combining the audio input signals to form a combined audio input signal; and utilising a Sigma-Delta Modulator to convert the combined audio input signal to a corresponding Sigma-Delta Modulated output signal. The method can include a linear mix of the audio input signals and each audio input signal can multiplied by a corresponding gain factor before being added together with other of the audio input signals. The Sigma-Delta Modulator can include a noise shaping filter designed to amplify components of the audio input signals below a predetermined threshold frequency and the combining step can include utilising a negative feedback of the combined audio input signal. The noise shaping filter can utilise a series of integrating circuits as a means to decrease the sensitivity of the filter to errors in its coefficients.

Abstract: An improved method and apparatus for filtering an electronic environment with relatively high accuracy and efficiency and relatively short flow-through delay ("latency") is disclosed. Embodiments of the invention may be applied to digital filters implemented in software, hardware or a combination of both for applications such as audio filtering or electronic modelling of acoustic system characteristics.