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本文对八个前兆性地声信号在沙层中的衰减特性,及其对鼠脑中5-羟色胺(5-HT)代谢的影响,进行了测量分析。主要结果如下: 1.八个地声信号在沙层中的衰减特性的图象基本相似,其基本特征相同的具有明显的一致性。50—100Hz和250—630Hz内的衰减与频率明显有关,100—250Hz的优势频段内的衰减比较平缓,该频段内20—30cm沙层的吸收系数为4×10~(-2)—6×10~(-2)dB/cm。 2.地声信号透入30cm沙层内的洞穴中,洞内声压级的相对衰减率与同深度沙层内相比较,呈现一定的下降现象,并与地声信号的基本特性有关。在优势频段内,单次性轰隆声、连续性“炒豆”声等和刮风声分别下降4.4±0.8％、3.5±0.3％和3.0±0.2％,连续性小鼓声的下降不明显。 3.静适应48小时的小白鼠,同时分别在105—85dB和76—66dB的地声信号的随机组合声中暴露30分钟,其脑内5-HT的代谢产物5-羟吲哚乙酸(5-HIAA)的含量分别比对照组增高24.7％和26.2％. 这些结果表明,前兆性地声波透入地表的频谱特征与介质的吸收特性有关。此时透入洞穴内的地声波,其优势频段虽然明显低于鼠的听觉敏感区,但对鼠是一种极不适应的低频噪声刺激,可直接影响到脑内5-HT的代谢过程。同时,洞穴可增强动物对噪声背景上的声信号识别。可见,前兆性地声波有可能是引起鼠等穴居动物
In this paper, the attenuation characteristics of eight precursor acoustic signals in sand layers and their effects on 5-hydroxytryptamine (5-HT) metabolism in rat brain were measured and analyzed. The main results are as follows: 1. The images of the attenuation characteristics of the eight ground acoustic signals in the sand layer are basically similar, with the same basic features and obvious consistency. The attenuation in 50-100Hz and 250-630Hz is obviously related to the frequency. The attenuation in the frequency band of 100-250Hz is relatively gentle. The absorption coefficient of 20-30cm layer in this band is 4 × 10 -2 -6 × 10 ~ (-2) dB / cm. 2. The ground acoustic signal penetrates into the caves in the 30cm sand layer, and the relative attenuation rate of the sound pressure level in the cave shows a certain decrease compared with that in the same depth sandstone, which is related to the basic characteristics of the ground acoustic signal. In the dominant frequency band, the one-way bang sound, the continuous “fried bean” sound and the wind-blowing sound decreased by 4.4 ± 0.8%, 3.5 ± 0.3% and 3.0 ± 0.2% respectively, while the decrease of continuous small drum sound was not obvious. 3. Quiescent 48-hour mice, respectively, while the ground sound signal in the 105-85dB and 76-66dB were combined for 30 minutes of exposure, the brain 5-HT metabolite 5-hydroxyindoleacetic acid (5 -HIAA) were 24.7% and 26.2% higher than those of the control group, respectively.These results show that the spectral characteristics of precursory acoustic penetration into the earth’s surface are related to the absorption characteristics of the medium. At this time, the ground acoustic wave penetrated into the cave, although its dominant frequency band is significantly lower than that of the rat’s auditory sensitive area, is a very unfavorable low-frequency noise stimulus to the mouse and can directly affect the metabolic process of 5-HT in the brain. At the same time, caves enhance animal recognition of acoustic signals on noisy backgrounds. Can be seen that the precursory sound waves may cause rats and other burrowing animals