The acoustic reach of the famous Bow Bells -- supposed to define the area of London where cockneys are born -- has shrunk dramatically in the last 150 years thanks to the rise of ambient noise.

To be "born within the sound of the Bow Bells" of the church of

St Mary-le-Bow is the traditional definition of a cockney. This was because most cockneys living in the City of London close to St Mary-Le-Bow moved east in the 1800s, but they remained devoted to the church and its associated sounds.


To coincide with the launch of the Times Atlas of London, noise consultants 24 Acoustics, have produced a sound map of London that shows how far the sound of the bells reaches in 2012 compared with 1851. Back then, the bells could be heard from the City of London, across Islington, Hackney, Tower Hamlets and into parts of Camden, Southwark, Newham and Waltham Forest. In 2012, on the other hand, the bells can only be heard in a small patch covering just the City and Shoreditch. Given that there are no maternity units in this area, the likelihood of any "true" cockneys being born is reduced significantly.

24 Acoustics used precision sound level measurements taken while the bells were tolling, taking into account the UK's prevailing wind, which comes from the southwest. It is this wind that causes the sound from the bells to travel eastwards, as you can see in the image embedded in this post, despite the fact that the output from the bells is equal in all directions from the church tower.

They found that the reach of the bells is affected by the ambient noise levels, which was significantly lower 150 years ago.

Without roads or aircraft, ambient noise levels in London would have been similar to those in a rural location -- between 20 and 25 "A-weighted decibels" in the evening. A-weighted decibels, or dBA, are an expression of the relative loudness of sounds in the air as perceived by the human ear. This means that the decibel values of sounds at low frequencies are reduced to account for the fact that the human ear is less sensitive at low audio frequencies below 1,000 Hz.


In 2012, ambient noise levels in London vary across the city, but are generally higher than 55dBA, thanks to busy roads, aeroplanes and noise from air conditioning units.

If you want to channel your inner-cockney, you can download an

MP3 of the St Mary-le-Bow bells from the Times Atlas website.