This part of ISO 17201 provides a computational model for determining the acoustical source level of projectile sound and its one-third-octave-band spectrum, expressed as the sound exposure level for nominal mid-band frequencies from 12,5 Hz to 10 kHz. It also gives guidance on how to use this source level to calculate the sound exposure level at a receiver position. This part of ISO 17201 is intended for calibres of less than 20 mm, but can also be applied for large calibres. Additionally, the data can be used to compare sound emission from different types of ammunition used with the same weapon. This part of ISO 17201 is meant for weapons used in civil shooting ranges, but is also applicable to military weapons. The computational method can be used as a basis for environmental noise assessment studies. The prediction method applies to outdoor conditions, straight projectile trajectories, and streamlined projectile shapes. Because of the latter, it cannot be applied to pellets. Default values of parameters used in this part of ISO 17201 are given for a temperature of 10 °C, 80 % relative humidity, and a pressure of 1 013 hPa. Annex A can be used for calculations in other atmospheric conditions. Particularly for calibres < 20 mm, the spectrum is dominated by high frequency components. As air absorption is rather high for these frequency components, calculations are performed in one-third-octave-bands, in order to allow a more accurate result for air absorption to be obtained