This part of ISO 17201 specifies methods for estimating the acoustic source data of muzzle blast and explosions and the source data of projectile sound on the basis of non-acoustic data for firearms with calibres less than 20 mm and explosions less than 50 g TNT equivalent. This part of ISO 17201 addresses those cases where no source measurements exist or where the data necessary to calculate projectile sound according to ISO 17201-4 are unknown. An example of this situation would be measuring projectile sound from shot guns pellets. This part of ISO 17201 can also be used as an interpolation method between measurements of muzzle blast. Source data are given in terms of spectral angular source energy covering the frequency range from 12,5 Hz to 10 kHz and can be used as data input for sound propagation calculation. This part of ISO 17201 is not applicable to the prediction of sound levels for the assessment of hearing damage and cannot be used to predict sound pressure levels or sound exposure levels below a specific distance where linear acoustics does not apply.