The reason behind the crackdown on Kigali entertainment spots that were generating more noise than they could contain seems to have been delivered home.

A significant number of them are restaurants, according to the City authorities, but were operating without the required permits to work as bars or night clubs. This resulted in sustained loud music and the attendant exuberant and rowdy, if inebriated patron noises characteristic of nightspots.

No one likes noise, especially if they are trying to sleep. According to the City authorities, the allowed noise levels should be about 70 decibels in commercial areas, and 50 decibels in residential areas.

What does this mean?

The pressure sound exerts as it reaches your ear through the air is measured in decibels (dB). And there is general agreement globally that exposure to sound levels less than 70 dB does not produce hearing damage, regardless of the duration of exposure.

To put these levels into perspective, according to various analyses, sound levels produced by the average refrigerator or the sounds in a typical quiet neighborhood measure about 45 dB. The 50 dB prescribed for Kigali residential areas are therefore safe.

Most environments contain a combination of sounds from more than one source, say, children at play in the fields; the goings on in the market; car horns and alarms and the revving noise they make in transit; aircraft, etc.

70 dB during the day does not bother the average citizen going about their business, but sound levels above 50 dB across the quiet night horizon can be annoying to many people.

Enforcing these levels cannot be faulted. Indeed, there is probably a need to look into other emitters of noise beyond the prescribed levels.

Take the cobblestoned (mawe) roads reminiscent of the ancient Roman via, that run through many of the Kigali suburbs.

No doubt they are aesthetic and help maintain the clean-City look by keeping away dust or mud depending on the season.

Yet, to drive through the mawe roads, they are not only expensive with the damage they inflict on vehicle suspensions and body parts, they so noisily rattle, but probably don’t meet the prescribed lawful noise levels in residential areas.

Chariots in ancient Rome were banned from the streets at night to prevent the clattered noise by wheels on paving stones that disrupted sleep and caused annoyance to the citizens.

Likewise, some cities in Medieval Europe either covered the stone streets with straw to reduce noise, or banned horses and horse drawn carriages from the streets at night.

Of course, our modern wheels cushion much of the noise. But moderate motor vehicle traffic at a distance of 30 metres rates about 50 decibels on a good tarmac road, never mind the mawe road with the rattling and all very close to homes.

To a driver with a car window open or a pedestrian on the sidewalk, the same traffic on tarmac rates about 70 dB, which is significantly louder.

The noise of heavy truck traffic on a busy road rates at about 85 decibels. And, according to the World Health Organisation, exposure for more than 8 hours to sound levels in excess of 85 dB is potentially hazardous.

However, the WHO recommends that unprotected exposure to sound levels greater than 100 decibels should be limited to duration of four hours at a frequency of about four times a year.At a distance of 600 metres, the noise of a jet takeoff reaches about 110 decibels, which is about the same as a car horn only one metre away.

The writer is commentator on local and regional issues