The sound frequency weighting PNdB has been proposed by Kryter (1959) to assess the noise from jet engine aircrafts. Due to the technical evolution of aircraft engines, and to choose a frequency weighting common to all transport systems, the dB(A-weighted) has begun to be used as the acoustical unit around airports; the PNdB is still used for noise certification purposes. A study of noise measurements that was carried out around French airports allows one to see some noticeable differences between acoustical levels, respectively, expressed in dB(A) and dB(C). The difference varies between 4 dB for the landing of recent aircrafts to 14 dB at take-off for 50/70-seat propeller aircrafts. If one considers the additional frequency decrease due to the walls and windows in housing, the pertinence of dB(A) weighting could be questioned for aircraft noise received by people living a long distance from the airport. This question is of interest in light of the new ANSI method for assessing combined noises (Schomer, 1997): this method suggests using the C frequency weighting for sounds with strong low-frequency content.