Sensorineural hearing impaired individuals have narrow hearing range, especially in high frequency. Due to acoustic diffusion masking, just amplifying speech can’t meet patients’ demands. Traditional methods restore the signal of high frequency in low frequency, which has two weaknesses. On the one hand high frequency covers low frequency, on the other hand the methods change the energy of speech. These two aspects severely decrease speech loudness, perception and recognition. To solve the above problems, we have proposed an improved frequency shifting compression method based on Auto Energy Gain Compensation (AEGC) which is used for hearing aids. Fully investigating the relationship of speech frequency with energy and recognition, the scheme selectively keeps the information of vital frequency band. Meanwhile, it compensates the speech loudness with AEGC module. With the proposed scheme, it has obviously improved the speech perception and recognition. Both the theoretical simulation result and subjective test in APP on android platform show the energy is compensated and the speech recognition ratios are enhanced 20%-30% in different environments, especially efficient in quiet, noisy and normal environment.

Recently, there is a growing trend to investigate wide dynamic range compression technique with the development of hearing aids. However, existing methods used to enhance expected speech as well as the background noise and classical linear compression can’t achieve the requirements of hearing impaired individuals’ reaction to the loudness compensation flexibly. To cope with the problems, this paper proposes a new approach to suppress the enhanced background noise and to dismiss abnormal sound caused by severe jittering from high frequency signal. What’s more, a scheme of curve compression is introduced to improve the loudness amplifying flexibility instead of conventional linear compression. Both the theoretical simulation and testing on cellphone hearing aid APP based on android system prove the proposed method can improve the performance of speech enhancement and provide more choices to strength sound with the curve compression ratio.

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