利用聲波檢測鴨蛋外殼裂痕之研究

The Study of Eggshells' Crack Detection by Acoustics

白世煜(Shih-Yu Pai) ； 紀偉民(Wei-Min Jee) ； 李仲暐(Chung-Wei Li) ； 鄭經偉(Ching-Wei Cheng)

《農林學報》 50卷4期 (2001/12) Pp. 79-102

https://doi.org/10.30089/JAF.200112.0006

摘要

本研究旨在提供－利用聲波檢測蛋殼裂痕的方法，使其能有效的應用在蛋殼裂痕檢測自動化系統的開發。本實驗先將銅管製成閉管的模式、分析銅管內空氣柱振動的諧振頻率、波長之間的關係。分析銅管正向直接敲擊蛋殼之頻譜圖，得知其第一諧振即為空氣柱在銅管內產生之基本頻率，且該頻率之振幅會因蛋殼的裂痕而降低。其次再利用集音管敲擊鴨蛋蛋殼，由集音管前端的鋼珠激振集音管內空氣柱，使其振動產生音波訊號，再以麥克風擷取之，並進行傳立葉轉換得到其基本頻率，得知該頻率之振幅亦會因裂痕的存在而哀減。因此，本試驗將以示波器直接比對振幅大小，並藉此判斷裂痕是否存在。實驗結果顯示：蛋殼裂痕處之振幅較完整處為低，且對於完整蛋所測得衝擊波之波形，其第二與第一峰值之比率介於70%與90%之間，然而對於裂痕蛋，若敲擊點在裂痕處則該比率介於30%至40%之間；若敲擊點在裂痕臨近處，則該比率介於50%至60%之間。位於裂痕處的第一諧振頻率之振幅是在-30dB以下，完整處的第一諧振頻率之振幅介於-27.1dB~-28.7dB之間，在裂痕臨近處的第一諧振頻率則是介於-28.7dB~-30dB間，利用此基礎資料即可判斷裂痕是否存在。

關鍵字

蛋 ； 聲波檢測 ； 諧振頻率

並列摘要

The purpose of this study is to offer a method for using acoustics detecting eggshells' crack in order to make an effective application to the development of the eggshells' detecting automatic detecting system. This experiment used different length of closed brass tubes to find the frequencies and wavelengths of air in the tube. According to the response spectrum, it was observed that the first natural frequency was the same as that in the brass tube. Besides, the frequency amplitude was decreased due to the existed cracks. Then, using the sound-gathering tube with a steel ball in front of tube to knock at the eggshells, the microphone received a sound-wave signal from the air in the tube. By means of the swift the FFT, it showed that the frequency amplitude was also decreased due to the existed cracks. Therefore, this experiment used oscilloscope to compare the amplitudes and to justify weather the cracks was existed or not. The experimental results showed that the amplitude of eggs with crack was lower that without crack. It also showed that all the ratio of the second peak to the first peak for the eggs without crack was ranged 70% to 90%. However, for the eggs with crack, the ratio was ranged 30% to 40% when knocking at the point of crack, and 50% to 60% when knocking at the point near the crack. The amplitude of the first natural frequency at the crack was under -30dB, between -27.1dB and -28.7dB. When the shell is perfect and between -28.7dB and -30dB beside the crack. The results will be identified as the base of detecting the eggshells' cracks.

並列關鍵字

Duck egg ； acoustics ； natural frequency