Audio spectral noise reduction method and apparatus

A noise reduction system for an audio signal, wherein the audio signal comprises spectral components, comprising:

• a processor;
• (a) a furrow filter;
• and
• (b) a bar filter;
• wherein the furrow filter is used to select spectral components that are narrow in frequency but relatively broad in time, and the bar filter is used to select spectral components that are broad in frequency but relatively narrow in time;
• wherein there is a relative energy distribution between the output of the furrow and bar filters, and said relative energy distribution is analyzed to determine the proportion of spectral components selected by each filter that will be included in an output signal;
• wherein, using the processor, the audio signal is reconstructed based on the analysis of the relative energy distribution between the output of the furrow and bar filters to generate the output signal;
• wherein the furrow and bar filters are referred to as the first pair of time-frequency filters, further comprising a second pair of time-frequency filters, wherein the second pair of time-frequency fitters is used to improve intelligibility of the output signal;
• wherein the audio signal comprises fricative components;
• wherein the second pair of time-frequency filters comprises a furrow filter and a bar filter;
• wherein there is a temporal relationship between the output of the furrow filters of the first and second pairs of time-frequency filters and the output of the bar filters of the first and second pairs of time-frequency filters;
• and
• wherein the temporal relationship between the furrow filter output and the bar filter output is monitored so that the fricative components are allowed at boundaries between intervals with no voiced signal present and intervals with voice components.