Vince M A, Billing A E, Baldwin B A, Toner J N, Weller C
Early Hum Dev. 1985 Jul;11(2):179-90. doi: 10.1016/0378-3782(85)90105-7.
In a first experiment a miniaturised radio hydrophone was implanted inside the amniotic sac in three pregnant ewes and recordings were made from 3 weeks before the lambs were born until they had emerged; these recordings showed that the sound of the mother's voice was slightly louder when picked up by the hydrophone inside the amniotic sac than when picked up by a microphone beside her flank and that sounds recorded during labour included long and loud low frequency sounds associated with contractions, and an increase, compared with before labour, in the incidence of sounds produced by the maternal cardiovascular system and by breathing. Over the last 3 weeks of gestation the attenuation of sounds from outside the mother decreased at frequencies between 500 and 4000 Hz, but not below or above those frequencies. In a second experiment the bleats of 23 pregnant ewes were recorded; their lambs were taken at birth and tested with the sound of either their own mother's bleats, or with bleats from an alien ewe. Heart rate changes which occurred during playback of maternal and alien bleats differed significantly, but only on the occasion when each lamb heard its first bleat, postnatally.
在第一个实验中，将一个小型化的无线电水听器植入三只怀孕母羊的羊膜囊内，并从羔羊出生前3周开始记录，一直到它们出生；这些记录表明，羊膜囊内的水听器接收到的母亲声音，比其胁腹旁的麦克风接收到的声音略大，并且分娩期间记录到的声音包括与宫缩相关的长而响亮的低频声音，以及与分娩前相比，母体心血管系统和呼吸产生的声音发生率增加。在妊娠的最后3周，来自母亲体外的声音在500至4000赫兹之间的频率处衰减减小，但在这些频率以下或以上则没有减小。在第二个实验中，记录了23只怀孕母羊的咩叫声；它们的羔羊在出生时被带走，并用自己母亲的咩叫声或外来母羊的咩叫声进行测试。回放母体和外来咩叫声时出现的心率变化有显著差异，但仅在每只羔羊出生后第一次听到咩叫声时出现这种情况。
