The shock response spectrum (SRS) allows to estimate transient acceleration signals in terms of a maximum response of a dynamic vibration system. Its origin probably dates from civil engineering and the problem of seismic excitations, i.e. earthquake response of buildings, see Clough Penzien 1975. The SRS is a spectrum, i.e. a curve giving the maximum acceleration response depending on frequency. It is derived from a 1-mass-spring-damper vibration system being excited by a base excitation, i.e. an acceleration. freesrs calculates the shock response spectrum (SRS) and is a small library with Python and Fortran files. The Fortran files consist of • SmallwoodFilter.f and • GenShockTimeHistories.f They are linked to Python by using the comfortable f2py tool. Latest version is 1.1.1, including now the ability to perform a full install via setup.py.