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

声学打开了一扇展示水下世界的窗户。光无法到达海洋深处，所以通常“看到”远处事物的唯一方法是观察反射的声波，而不是光波。近四分之三世纪以来，海洋学家一直使用声纳技术来了解海洋内部。然而，这个强大的工具也有一些局限性。使用标准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浓度或相互作用的洋流之间的混合量变得棘手。问题是我们一直局限于用黑白来“观察”海洋。传统的窄带声呐只使用单一的声波频率。这就像只看一种颜色的世界，因为颜色是由被物体优先反射的光的频率决定的。限制我们的眼睛只观察一种频率的光，就像观察黑白世界一样。显然，当我们看到物体的全色时，我们更容易识别它们。为此，我建议购买一个宽带声纳系统。这项新兴的技术可以观察到海洋中更广泛的声散射频谱。这个航海仪器将是我研究项目的基石。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变化的信息——转化为有用的海洋学测量。我在达尔豪斯大学和加拿大其他地方的同事都热衷于使用这种新仪器。这种宽带声纳将为加拿大的海洋学研究增添色彩。

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.