基于二次对数能量熵小波包的母猪哺乳声去噪方法研究

Denoising Method of Log Energy Entropy Quadratic Wavelet Packet in Sows' Lactating Vocalization

以小梅山母猪发出的哺乳呼噜声及其它干扰噪声为研究对象，利用噪声能量在频域内均匀分布，其对应的信息熵值最大的特性，根据噪声类型不同，选择不同小波包层数结合信息熵计算，去除环境噪声混叠的影响。试验结果表明，母猪呼噜声的频率范围在0～800Hz内，仔猪争乳尖叫声的频率大于1000Hz，其他干扰噪声的频率范围0～8000Hz内；分别经过5层和3层的dbl0小波包分解，利用对数能量熵软阈值去除0～8000Hz主噪声及i000～8000Hz内的残留噪声，且重构信号中母猪哺乳声的波形特征保持较好，获得令人满意的滤波处理结果，为进一步研究畜舍环境下母猪哺乳声音特征提取及识别提供了数据预处理方法。

Nurse grunting of lactating sows, as a signal to attract piglet sucking, the frequency of which has a fixed relationship with the motive of sow＇s milk secretion, will benefit for building a feeding pattern between the sow and its＇ piglets. As an important trait of good maternal behavior, nurse grunting can be one of the criterion in maternal behavior. However, the noises from environment and piglets screams often disturb the recognition and extraction of time- and frequency-domain characteristics. The nurse grunting of Xiaomeishan sows combining with the noises from environmental interference noise and piglets＇ screaming calls were used in this study. Firstly, according to the energy of noise is even-distributed in the frequency domain, which corresponds to the maximum entropy characteristics, the layers of wavelet packet was selected, and the entropy of corresponding wavelet packet coefficient was calculated. Secondly, the power ratio was calculated to distinguish the types of noise. Finally, the different denoising methods in sound signal with different kinds of noise were compared. The results showed that the main frequency range of a nurse grunting was ranged from 0 Hz to 800 Hz, while the frequency of piglets＇ screaming calls was ranged from 1 000 Hz to 8 000 Hz, and the frequency of other interference noise was distributed from 0 Hz to 8 000 Hz. The power ratios of 0 Hz to 1 000 Hz in pure nurse grunting without noise, with environmental noise, and with screaming calls were 1, between 0. 85 to 0.97, and between 0 to 0.8, respectively. Meanwhile, with dbl0 as a wavelet packet basis, the 5 layers and 3 layers wavelet packet transform were used, the main noise ranging from 0 Hz to 8 000 Hz and residual noise ranging from 1 000 Hz to 8 000 Hz can be removed. Therefore, the reconstructed signal can be used to analyze the feature of nurse grunting in Xiaomeishan sows.