Network studies are directed toward effective utilization of a collection of seismic stations as a coherent worldwide seismic network to lower the detection threshold for seismic events and improve their classification. This report presents an analysis of ambient seismic noise seen at the network level and is directed toward characterization of the network noise field. Simultaneously recorded noise samples from two VELA stations and eight LRSM stations are investigated through analysis of power-density spectra, coherence, high-resolution frequency-wavenumber spectra, and K-line spectra. The ambient short-period network noise field is found to be highly variable with time and with geographical position. Variations in noise power are directly related to regional storm activity. Dominant noise power at most stations is trapped-mode surface-wave energy that does not exhibit useful interstation coherence.