Hydrogen Speed-of-Sound Literature Data Compilation

This dataset is a compilation of published speed-of-sound measurements for hydrogen — normal, para, equilibrium, or composition-unspecified hydrogen — drawn from the experimental literature up to 2024 (the most recent relevant publication as of 2026-07-14), covering cryogenic to above-ambient temperatures (roughly 14–350 K) at pressures up to approximately 100 MPa. Each source is provided as one or more plain-text Property Information File (PIF) datasets, organised by composition and phase and carrying the DOI of the original publication, alongside a master summary index and a Python reader (pif_reader.py) for parsing and combining them. It was compiled within the CryoMet project (European Partnership on Metrology) in support of activity A4.2.1. See README.md for the format, schema, and usage. The project (24GRD07 CryoMet) has received funding from the European Partnership on Metrology, co-financed from the European Union's Horizon Europe Research and Innovation Programme and by the Participating States. Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or EURAMET. Neither the European Union nor the granting authority can be held responsible for them.