About 1 in 3 Seoul citizens considers noise to be one of the worst environmental problems in the city, a report showed Sunday.

According to Seoul Institute’s survey conducted on 1,032 citizens, 33.6 percent picked noise as the second-most serious environmental issue after air pollution.

By type, traffic noise led with 42.4 percent, followed by noise from apartment neighbors and from construction, with 23.1 percent and 12.9 percent, respectively.

A total of 1,271 cases of loud sounds heard from upper floors in apartments were reported in Seoul last year ― an average of 3-4 cases per day.

Of those surveyed, 35 percent answered that night noises were considerably bothersome and 20 percent thought late-night noises were also serious.

Levels of late-night noises in 15 out of 25 Seoul districts, measured in 2011, were found to have ranged between 46 and 54 decibels. This is about 10 decibels higher than the World Health Organization’s recommended level ― 40 decibels late at night.

If the noise rises by 10 decibels, humans perceive the noise as twice as loud, the report said.

The number of noise complaints in the capital nearly doubled in 2011 in five years, reaching 21,745 cases, it added.

The institute pointed out that most of the noise management measures take place after complaints. It advised the city to take preventive measures based on scientific investigations and comprehensive research.

By Lee Hyun-jeong (rene@heraldcorp.com)