When you think of the word “calm”, surely the most likely image to come to mind is that of tennis great John McEnroe. Thanks to meditation and sleep app “Calm”, you can now be soothed by the dulcet tones of McEnroe himself, as he reads you the rules of tennis:

“Tennis balls are made of hollow, vulcanized rubber with a felt coating. The predominant color is optic yellow for improved visibility…The International Tennis Federation defines the official diameter (of a tennis ball) as 65.41 to 68.58 mm. Balls must weigh between 56.0 and 59.4 grams.”

Enjoy!