A number of years ago, in collaboration with Ultra Electronics Maritime Systems, GeoSpectrum Technologies Inc. invented a new method of building low frequency sound projectors. Rather than building a projector as a single large structure as is traditionally done, the new method uses multiple small projectors, hence its name, Modular Projector System or MPS. The quantity and physical arrangement of the projector modules determines the resonance frequency, acoustic power and bandwidth of the system.
A MPS is assembled from a plurality of flexural disc projectors, or benders as they are sometimes called. Bender technology has been employed since 1950 and is well understood, inexpensive, and reliable. Benders are shaped like a pancake: large diameter compared to the thickness. The bender comprises four components: two circular, piezoelectric ceramic plates which are bonded to two circular metal plates. The metal plates create an air-filled cavity. A voltage applied to the ceramic causes the plates to bend, thereby radiating sound. The figure below shows a schematic of the cross section of a bender, and picture of a potted bender (potted so it could be calibrated).
Figure 1 Cross section and photograph of a bender
To create an MPS, benders are assembled in a stack, like a stack of pancakes, with milli-位 separations between benders. Once assembled, the stack is encased in a boot. To increase the quantity of benders, stacks can be arranged side by side or on top of one another. The figure below shows a one-stack and four-stack MPS being calibrated at Seneca Lake.
Since its invention, many MPSs have been modeled, built, and calibrated. The first MPSs could fit into the palm of your hand and were used to study and confirm the physics of MPS. Many generations followed with the latest generation shown in the photo (below), a 400 kg system being calibrated in Bedford Basin, Nova Scotia.
GeoSpectrum is now building MPS modules suitable for a high resolution coherent seismic source and is developing a low frequency system for oil exploration with support from PRAC.
The beauty of an MPS is that you can achieve whatever level of acoustic performance that is desired without fundamentally redesigning the projector; it is just a matter of adding more modules to achieve greater power and bandwidth. Powerful, low-frequency sources are necessarily large, but if you can tolerate the size, weight, and cost, you can specify the power you want and MPS can achieve it.
A MPS is inherently more reliable that a conventional projector, which is either working or broken; there is usually no middle ground. On the other hand, a MPS uses a quantity of benders and the failure of a few benders does not appreciably affect performance.
Furthermore, on a routine maintenance schedule, failed stacks can be replaced in the field, and failed benders within a stack can be replaced in the factory.
Please contact us for further details or to discuss your specific needs.