Application of equal loudness contour in assessing the impact of random noise: Case study in continuous positive airway pressure systems with helmet

Empirical evidence is presented on the application of equal-loudness contour for assessing the exposure to noise to which patient are subjected when receiving continuous positive airway pressure respiratory support via a helmet. Sound pressure levels are compared in one third-octave bands with respect to the isophon lines and the influence of the heat and moisture exchanger filters coupled to the helmets on the sound pressure levels during the supply of air–oxygen is analyzed. This study has demonstrated that an appropriate change of scale enables a more objective assessment of the whole auditory spectrum and the levels of noise produced by the continuous positive airway pressure respiratory support via a helmet exceed the 40-phon line and levels of 45 dB(A) recommended by various organizations.