The spatial coherence is frequently used to summarize the impact of the propagation environment on array performance and to suggest a limitation on useful array aperture. In general coherence implies a fixed phase relationship and involves time as well as space. The array gain is a metric to measure the performance of an array. In order to calculate the array gain, the spatial coherence is widely used. In the presentation the array gain is calculated for line array in isotropic noise and directional noise environment.time as well as space. The array gain is a metric to measure the performance of an array. In order to calculate the array gain, the spatial coherence is widely used. In the presentation the array gain is calculated for line array in isotropic noise and directional noise environment.