A mysterious, metallic sound that has been recorded in Mariana Trench, the world's deepest part of the oceans, might be from a minkle whale, according to a US-based research. Dubbed as the "Western Pacific Biotwang", the sound includes frequencies spanning from as low as 38 hertz to as high as 8,000 hertz and lasts between 2.5 seconds and 3.5 seconds.