Siemens Medical Instruments Pte. Ltd.

Siemens Audiologische Technik Gmbh

Ruhr-universitaet Bochum

Ruhr-universitat Bochum

Timo Gerkmann

Rainer Martin

Colin Breithaupt

Henning Puder

Wolfgang Soergel

Rainer Professor Martin

A filter bank with a sufficiently high resolution for amplification and noise reduction and with the lowest possible computational complexity is provided for a hearing device and, in particular, for a hearing aid. Two-stage frequency transformation with little latency is therefore proposed for hearing aids. Some of the processing, for example the amplification, is carried out after high stopband attenuation in the first stage. An increased frequency resolution is achieved in a second stage before the back-transformation in the first stage, which is favorable for noise reduction, for example.

Hearing device and method for operating a hearing device with two-stage transformation

A smoothing method for suppressing fluctuating artifacts in the reduction of interference noise includes the following steps: providing short-term spectra for a sequence of signal frames, transforming each short-term spectrum by way of a forward transformation which describes the short-term spectrum using transformation coefficients that represent the short-term spectrum subdivided into its coarse and fine structures; smoothing the transformation coefficients with the respective same coefficient indices by combining at least two successive transformed short-term spectra; and transforming the smoothed transformation coefficients into smoothed short-term spectra by way of a backward transformation.

Smoothing method for suppressing fluctuating artifacts during noise reduction

A method for modification of a cepstro-temporally smoothed gain function of a gain function resulting in a bias compensated spectral gain function is provided. The cepstro-temporal smoothing increases the quality of an enhanced output signal, as it affects only spectral outliers caused by estimation errors, while the speech characteristics are well preserved. However, due to the cepstral transform, the temporal smoothing is done in the logarithmic domain rather than the linear domain, and hence results in a certain bias. Thus, the method for a general bias compensation for a cepstro-temporal smoothing of spectral filter gain functions that is only dependent on the lower limit of the spectral filter-gain function.

Method for bias compensation for cepstro-temporal smoothing of spectral filter gains

A method for determining unbiased signal amplitude estimates () after cepstral variance modification of a discrete time domain signal (s(t)), wherein the cepstrally-modified spectral amplitudes () of the discrete time domain signal (s(t)) are &#x3c7;-distributed with 2{tilde over (&#x3bc;)} degrees of freedom. A bias reduction factor (r) is determined using the equation where 2&#x3bc; are the degrees of freedom of the &#x3c7;-distributed spectral amplitudes of the discrete time domain signal (s(t)) and then the unbiased signal amplitude estimates () are determined by multiplying the cepstrally-modified spectral amplitudes () with the bias reduction factor (r) according to the equation=r. A method for speech enhancement and a hearing aid use the method for determining unbiased signal amplitude estimates () in order to offer the advantage of spectral modification, such as smoothing, of spectral quantities without affecting their signal power.

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Timo Gerkmann