The Pacific Islands Passive Acoustic Network (PIPAN) is a collection of 14 sites spread across the Central and Western Pacific Ocean from American Samoa in the south to Pagan in the west to Manawai in the north, and the Big Island of Hawaii in the east. At each site a bottom-mounted High-frequency Acoustic Recording Package (HARP) instrument was deployed. These instruments were developed and processed in collaboration with the Scripps Institution of Oceanography and NOAA Pacific Islands Fisheries Science Center (PIFSC), with funding from PIFSC, the U.S. Navy and the Ocean Acoustics Program at the National Marine Fisheries Service Office of Science and Technology. The sites were specifically selected for the detection, classification and long-term monitoring of cetaceans in remote locations or areas of particular interest, and were initially focused on deep-diving species such as beaked whales and sperm whales. The data have subsequently been used for a variety of purposes, such as monitoring of surface-living cetaceans (e.g. delphinids, baleen whales), soundscape monitoring, and habitat modeling. The recordings allow the assessment of changes in vocalizations or distributions that might be related to increasing human sounds or changes in environmental conditions. The data began as early as 2005 at some sites, and are ongoing at selected sites through 2025. The duration of recordings at each site ranges from a few months to over 10 years. At sites with longer time series the data have intermittent gaps due to limited access to remote sites and issues with equipment. The instruments recorded frequencies from 10 Hz to 100 kHz or 160 kHz depending on the deployment. This dataset includes raw acoustic recordings from the HARP deployments and several associated files, which include calibration files (transfer functions) and two readme files that provide details on the acoustic recordings' xwav/flac format and descriptions of transfer functions. All recordings are collected in UTC. Amplitude calibration files called "transfer functions" are associated with the specific HARP equipment used to collect each acoustic recording dataset. Correct use of transfer functions is critical for providing absolute measured sound pressure received levels in standard acoustic measurement units, and for comparing signals within and between deployments. Transfer functions are estimates of a recording system's true sensitivity, and are being continuously evaluated and improved by Scripps Institution of Oceanography researchers and are subject to change without notice. Please review the Transfer_Function_readme before using this data.

All recordings have been converted to flac format from extended wav (x.wav) format. The xwav header information has been preserved in the conversion to flac format by using the --keep-foreign-metadata flag when compressing the data, however the header byte locations are not correct while the data remain in flac format. To retain the header information when decompressing from flac back to xwav, the --keep-foreign-metadata flag should also be used.