Abstract: A method for inspecting a conduit comprising the steps of: emitting an outgoing signal into the conduit to establish an acoustic plane wave within the conduit; and detecting a reflected outgoing signal from the conduit, wherein the outgoing signal is arranged such that low frequency components contribute to more of the outgoing signal, from a time perspective, than high frequency components.

Abstract: A method for inspecting a conduit comprising the steps of: emitting an outgoing signal into the conduit to establish an acoustic plane wave within the conduit; and detecting a reflected outgoing signal from the conduit, wherein the outgoing signal is arranged such that low frequency components contribute to more of the outgoing signal, from a time perspective, than high frequency components.

Abstract: An acoustic ground coupling device comprises a housing compartment filled with particulate material. The housing compartment further comprises at least one acoustic source for generating an acoustic signal and at least one acoustic sensor that detects, for example, back-scattered acoustic signals from the ground.

Abstract: An acoustic detection system is provided for determining the source of an acoustic wavefield. The system comprises multiple acoustic sensors, the sensors being configured to provide multiple different components of a vector from the source of the acoustic wavefield to the system.

Abstract: There is provided a system for monitoring and/or surveying a conduit, comprising at least one acoustic source for emitting a signal to propagate along the conduit, and at least one acoustic detector for receiving reflected signals.

Abstract: A method and apparatus for instantaneously measuring the level of carbon dioxide (and other gases) in automotive combustion exhaust analysis is provided in the form of a portable battery driven roadside diagnostic instrument in which the CO.sub.2 level is measured by a calorimetric technique utilizing light as the energy source and a piezoelectric bimorph to vibrate a single fiber-optic element to multiplex between two fiber-optic receptors delivering the light to a measurement cell and a reference cell. The measurement cell comprises a salt of an acid-base indicator dye which provides proportional color change on contact with CO.sub.2. The dye is supported on a polymetric film in the cell.