母羊3种应激行为下叫声信号的对比分析

为研究母羊在不同应激行为下叫声信号所具有的特征,选择体重相近、年龄在2~3岁的小尾寒羊母羊20只,分别录取其在3种应激行为(产羔、寻羔、饥饿)下的叫声信号。利用LabVIEW软件设计母羊发声信号特征提取与识别系统,对母羊发声信号进行时域分析、频域分析(Yule-Walker法估计功率谱、Welch法估计功率谱、线性坐标功率谱和倒谱分析)和时频域分析,提取发声信号的时间间隔、持续时间、主峰频率、能量集中范围和基音周期等特征参数。结果表明:母羊3种不同类型声音的持续时间以及主峰频率均存在显著差异(P0.05)。母羊在寻羔和饥饿时发声的持续时间是产羔时的1.93和1.82倍,饥饿叫声的主频分别为产羔和寻羔时的34.77和38.81倍,母羊叫声信号Yule-Walker法功率谱在饥饿出现1个峰值,寻羔时出现2个峰值,而产羔时无明显峰值。叫声信号能量在产羔时集中在400~600Hz,寻羔和饥饿时集中在0~900Hz,3种叫声基音周期接近为0.1ms。证明母羊叫声信号在3种应激行为下有明显的不同,因此可以作为评价其健康状况及福利化养殖水平的重要指标之一。

Comparative analysis of ewe's vocal signals under three stress reactions

To investigate the characteristics of ewe''s vocal signals under different stress behaviors,twenty 2-3 year-old small-tail Han sheeps with similar body weight were chosen and their vocal signals were collected respectively under three stress behaviors including delivering,seeking for lamb,and hungry.A system to process and identify the vocal signals was designed with LabVIEW,by which the signals were analyzed in time domain,frequency domain (power spectrum estimation of Yule-Walker method,Welch method,linear coordinate power spectrum and cepstrum method) and time-frequency domain.And then the characteristic parameters of vocal signals were extracted including time interval,duration,main peak frequency,energy concentration range,etc.The results demonstrated that the ewe''s call signals under three stress reactions showed significant differences in duration and peak frequency (P<0.05).The duration of ewe''s vocalization when seeking for baby and hungry was 1.93 and 1.82 times respectively than that of lambing;while the main peak frequency when hungry was 34.77 and 38.81 times higher respectively than lambing and seeking for baby.The Yule-Walker power spectrum detected one peak when hungry,two peaks when seeking for baby,and no apparent peak when lambing.The sound signal energy of ewe was concentrated within the range of 400~600 Hz when lambing,0~900 Hz when seeking for baby and hungry;the pitches of three sounds are all close to 0.1 ms.In conclusion,the call signals can reflect the changes of the external environment and physiological conditions of ewes,and it can be used as one of the important evidence for sheep health monitoring and welfare evaluation.