The aim of this paper is to evaluate the impact of exposure to low-frequency noise in residential areas, where there are power poles and power lines, in the human auditory system. A methodology to assess discomfort due to the low-frequency noise as well as audiometric tests exclusively for the low frequencies is proposed. Two predominantly urban areas were defined in Northwest Portugal to test the methodology. An “exposed” and “unexposed” study was used; the first group was highly exposed to the source under study and the second had no record of exposure to high voltage lines. To develop the research, a methodology was used to assess the discomfort due to low-frequency noise using audiometric tests (based on ISO-8253-1/2010) to determine the hearing threshold for pure sounds and recorded sound, as well as cognitive tests (Mini-Mental State Examination—MMSE). The average hearing threshold for recorded sound of the eight individuals tested in the “exposed” group was 51.3 dB, ranging from 40 to 65 dB, while the mean of the six subjects in the “unexposed” group was 24.1 dB, ranging from 20 to 30 dB. Based on the results obtained, the “exposed” group seems to be less sensitive to the low frequencies when compared to the “unexposed” group. The methodology used is adequate for a subjective assessment of the discomfort due to low-frequency noise.