29 of NYC's 30 quietest days in the last 3 years have been during the pandemic. It's as if every day sounded like Christmas in New York.

Today in Upshot @emilymbadger and I dive deep into the sounds of cities under lockdown. https://www.nytimes.com/interactive/2020/05/22/upshot/coronavirus-quiet-city-noise.html

Noise pollution researchers @sonycproject have been recording snippets of sound in the city for over three years. What they found was that in some parts of the city, sound levels dropped over 5 decibels. Here's one block in Noho.

We have audio samples before and after lockdown too. Samples from NYC, London and Venice (thanks @f_aletta and Jian Kang).

What you can hear is that the high frequencies of cars and chatter are gone. Now all you can hear is the enduring hum of wind and the sound of birds.

Using machine learning techniques researchers were able to classify sounds and how they have changed.

Frequency of:
cars driving is unchanged
traffic sounds have fallen
conversations has fallen

And those sirens? For the most part the freq of siren actually fell, probably due to lower police activity. But siren freq did spike for one mic in Queens, near a fire station and highway.

The number of mics are limited and not evenly distributed throughout the city so ymmv.

Clapping! They were also able to document the change in city sounds at 7pm, where clapping for essential workers raised sound levels more than 6 decibels on avg.

It also seems that the intensity for the clapping has stalled. Here is the difference peak and ambient sound levels around 7pm over time.

Some people are freaked out by the silence. Some find it peaceful.

One fun fact we learned was that the birds are likely chirping more quietly now, as their bird calls tend to rise and fall with sound level of their environment.

Quiet in a city is rare. And one point a lead researcher @markbcartwright emphasized was that this is an opportunity for us to reimagine what our ideal city could sound like, now that we have a sense of what it sounds like at baseline.

Big thanks to @markbcartwright @say_project @mfu3ntes and the @joinsonyc team as well as @f_aletta and Jian Kang for putting together their sounds and research together on such short notice.

Btw I tagged the wrong SONYC in the last tweet. It's actually @sonycproject!