Broadband sonar for mapping turbulent and double-diffusive microstructure and plankton in the ocean

声学打开了一扇窗户，展示了一个水下世界。光不能到达海洋的深处，所以通常情况下，要“看到”远处的东西，唯一的方法就是观察反射的声波，而不是光波。近四分之三个世纪以来，海洋学家一直使用声纳技术来了解海洋内部。然而，这个功能强大的工具确实有一些限制。使用标准的窄带声纳很难区分不同的散射源。这使得应用定量数据分析来确定鱼类或浮游生物的密度，或相互作用的洋流之间的混合量变得棘手。问题是，我们一直在限制自己，以黑白方式观看海洋。传统的窄带声纳只使用单一的声频。这就像只看一种颜色的世界，因为颜色是由物体优先反射的光的频率决定的。限制我们的眼睛只能观察一个频率的光，就像观察黑白世界一样。显然，当我们看到物体的全彩时，我们更容易识别它们。为此，我建议购买一个宽带声纳系统。这项新兴技术使人们能够观测到海洋中更宽频谱的声波散射。这个远洋仪器将是我研究计划的基石。它将把我在实验室开发的宽带声学方法--从光谱数据中提取浮游生物大小和流体性质的可变性信息--转变为有用的海洋测量。我在Dalhousie和加拿大其他地方的同事们都热衷于使用这种新颖的乐器。这种宽带声纳将为加拿大的海洋研究增添色彩。

Acoustics opens a window revealing an underwater world. Light cannot reach the oceans' depths, so often the only way to "see" something at a distance is through the observation of reflected sound waves rather than light waves. For nearly three quarters of a century oceanographers have used sonar technology to learn about the ocean interior. This powerful tool does, however, have some limitations. Using standard narrowband sonar it is difficult to distinguish between different sources of scatter. This makes it tricky to apply quantitative data analysis to determine concentrations of fish or plankton, or the amount of mixing between interacting ocean currents.The problem is that we have been limiting ourselves by "viewing" the ocean in black and white. Traditional narrowband sonar uses only a single acoustic frequency. This is like viewing the world in only one colour, since colour is determined by the frequencies of light that are preferentially reflected by an object. Restricting our eyes to observing only one frequency of light is like observing the world in black and white. Clearly, we have a much easier time identifying objects when we see them in full colour.For that purpose I propose to purchase a broadband sonar system. This emerging technology allows the observation of a wider frequency spectrum of acoustic scatter in the ocean. This sea-going instrumentation will be the cornerstone of my research program. It will turn the broadband acoustic methods I have been developing in the laboratory-extracting information on plankton size and variability of fluid properties from spectral data-into useful oceanographic measurements. My colleagues at Dalhousie and elsewhere in Canada are keen to use this novel instrument. This broadband sonar will give colour to oceanographic research in Canada.