Black adults hear better than white adults, a government study found.
The study also found that women hear better than men, and that overall, hearing in the United States is about the same as it was 35 years ago, despite the advent of ear-blasting devices such as the Walkman and the iPod.
Previous research reached similar findings about racial and sex differences, but the new study by scientists with the federal National Institute for Occupational Safety and Health was the largest national sample to report such a finding, experts in acoustics said.
The racial difference may be related to melanin, a skin pigment. Some scientists believe black people’s larger amounts of melanin protect them from noise-induced hearing loss as the years go by, study researcher William Murphy said. Scientists suspect melanin plays a role in how the body removes harmful chemical compounds caused by damage to the sensitive hair cells in the inner ear.
Genetics or the amount of noise exposure may explain the difference between women and men, said Elliott Berger, an Indianapolis-based hearing protection expert.
“Boys have typically done noisier activities,” Berger said.
The conclusion that the nation’s overall hearing has not changed since the early 1970s seems to contradict other recent research finding that modern teenagers do not hear as well as children did in the age before mobile listening devices, Berger said.
“You’d think society is noisier now — iPods are ubiquitous,” Murphy said.
The study, reported at a scientific conference last week, looked at more than 5,000 people who had hearing tests from 1999 through 2004 as part of a comprehensive, annual federal health survey that includes physical examinations.
The 10- to 20-minute hearing test involves wearing headphones and pressing a button when a tone is heard. Both frequency and loudness, or decibels, are measured.
People who can hear higher-frequency tones are better at differentiating certain sounds, such as “list” versus “lisp,” Murphy said.
On average, the 1,077 non-Hispanic blacks in the study could hear higher tones at 15 to 22 decibels, the study found. The 1,245 Mexican Americans could hear high-end tones at 16 to 25 decibels, on average. The 2,518 non-Hispanic whites could hear high-end tones at 21 to 32 decibels, on average, Murphy said.
Women on average were more sensitive to higher frequency tones. They could heard higher tones at 11 to 22 decibels, compared with 19 to 32 decibels for men.
Overall, the results were mostly the same as in hearing tests done from 1971 to 1975, Murphy said.