SUMMARYA method is presented to accelerate the execution of integral equation time domain analyses of exterior acoustic scattering problems. Conventionally, these have costs which scale with the "fth power of the frequency of the excitation, and practical limits to such computations are reached when bodies approach perhaps &5}10 wavelengths long. The fast approach presented is based on exploiting the pulsed nature of the illumination to omit much nugatory calculation. There is an associated slight accuracy loss; this is investigated. The method has costs which can scale with frequency to the power as low as &3, such that, for example, costs on a 18)5 wavelength body are reduced by a factor of about 28, with this factor itself increasing with roughly the square of the body size. Associated with the reduction in operations is a reduction in the scaling of storage required, from the third to the second power of frequency. Examples of analysis of large scatterers are presented, extending to a &22 000 node &almond'.

A method is presented to accelerate the execution of integral equation time domain analyses of exterior acoustic scattering problems. Conventionally, these have costs which scale with the "fth power of the frequency of the excitation, and practical limits to such computations are reached when bodies approach perhaps &5}10 wavelengths long. The fast approach presented is based on exploiting the pulsed nature of the illumination to omit much nugatory calculation. There is an associated slight accuracy loss; this is investigated. The method has costs which can scale with frequency to the power as low as &3, such that, for example, costs on a 18)5 wavelength body are reduced by a factor of about 28, with this factor itself increasing with roughly the square of the body size. Associated with the reduction in operations is a reduction in the scaling of storage required, from the third to the second power of frequency. Examples of analysis of large scatterers are presented, extending to a &22 000 node &almond'.