Fig. 17
From: Signal enhancement for communication systems used by fire fighters
Evaluation results. a Power spectral densities of the full-face mask FPS 7000 without a communication system (blue), with an activated voice amplifier of the communication system FPS-COM 7000 (black), and the artificial head without a full-face mask (red). b Difference of the power spectral densities from the full-face mask FPS 7000 with an activated voice amplifier of the communication system FPS-COM 7000 to the full-face mask FPS 7000 without a communication system