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AssigneeLenbrook Industries Limited
InventorsPeter Graham Craven, John Robert Stuart
Estimating the term…
Methods and devices are described for reducing the audible effect of pre-responses in an audio signal. The pre-responses are effectively delayed by employing a digital non-minimum-phase filter, which includes a zero lying outside the unit circle in its z-transform response. This zero is not paired with another zero at a reciprocal position inside the unit circle, as this would linearise the phase modification. The filtering can introduce a greater group delay at the pre-response frequency than at a low frequency, such as 500 Hz or even 0 Hz. The technique can be used to reduce pre-responses in an existing audio signal and also to pre-empt pre-responses that would be introduced to the audio signal by subsequent processing.
A method for reducing the audible effect of a pre-response having energy at a pre-response frequency, the method comprising:
A method for reducing the audible effect of a pre-response having energy at a pre-response frequency, the method comprising:
A method according to any preceding claim, wherein the filtering preconditions the digital audio signal to reduce a pre-response that will be generated in a subsequent upsampling process.
A method according to any preceding claim, wherein the pre-response frequency lies within 20% of a reference Nyquist frequency equal to one half of a reference sampling frequency that is less than or equal to the sampling frequency of the digital audio signal.
A method according to any preceding claim, wherein the z-transform response of the filter also includes a pole lying inside the unit circle at a reciprocal position to the zero, the pole and zero together selected to create an all-pass factor in the transfer function of the filter.
Dependencies are inferred from the claim text.