Demeester et al (2009) evaluated 1,147 subjects (549 males, 598 females, all between ages 55 and 65 years) to determine the prevalence of particular shapes (i.e., configurations) of their audiograms, not to determine presbycusis rates. All subjects were examined clinically, had otoscopy, and completed a medical history and environmental exposure questionnaire. Subjects with ear disease or genetic or other pathologies related to hearing loss were excluded.

Air conduction thresholds were gathered at 125, 250, 500, 1000, 2000, 3000, 4000, 6000 and 8000 Hz. Six categories were used to describe audiometric shape: (1) flat, (2) high-frequency gently sloping, (3) high-frequency steeply sloping, (4) low-frequency ascending, (5) mid-frequency U-shape, and (6) mid-frequency reverse U-shape.

After analysis, it was determined that low-frequency ascending, mid-frequency U-shape, and mid-frequency reverse U-shape appeared in less than 1 percent of the total subject population, (nine subjects), thus the nine subjects were eliminated form the subject analysis.

In males, high-frequency steeply sloping occurred 41 percent of the time, high-frequency gently sloping occurred 35 percent of the time, and flat occurred 24 percent of the time. In females, flat configurations occurred 50 percent of the time, high-frequency gently sloping occurred 36 percent of the time, and high-frequency steeply sloping occurred 14 percent of the time. Therefore, overall, for the entire study population, flat hearing losses were the most common.

(Source:http://www.audiology.org)