Abstract: Methods and devices for reducing intermodulation distortion are described herein. In response to receiving an audio input signal, N filtered audio signals may be generated by a filter bank, corresponding to N different frequency bands. The N filtered audio signals may be delayed by a delay time D, and a determination of whether an audio frame of the filtered audio signals includes an audio event or a non-audio event. A signal level estimation may then be determined, the signal level estimation indicating an expander, a compressor, or no compression effects being present. An amount of gain is determined and applied to the delayed audio signals, which are summed across the N frequency bands to generate a full-band audio signal. In some embodiments, the full-band audio signal may be applied to a limiter to reduce any audio clipping, and a final audio signal may be generated.

Abstract: A reconfigurable filter bank system that has an asymmetrical tree structure with multiple stages to generate multiband outputs. Each stage may include cascaded low-pass filters (LPFs), cascaded high-pass filters (HPFs) and/or all-pass filter(s) (APF(s)) having identical phase responses. As the cascaded LPFs, cascaded HPFs and APF(s) have identical phase responses, each frequency band of the multiband output may have an identical phase shift such that the frequency bands are in-phase and can be added together. The multiband outputs of the reconfigurable filter bank may have near-perfect reconstruction (e.g., small number of cross-band ripples) and therefore only minor distortion. In addition, the number of frequency bands and corresponding non-uniform bandwidths (e.g., frequency ranges) may be user-adjustable and/or reconfigurable during device operation. Further, the reconfigurable filter bank may have reduced computational complexity and/or latency.