Often in ordinary American speech the T sounds like a D. This happens when the T is after a vowel or an R, and before an unstressed vowel. It also happens in some other cases. It’s optional to use the flap T, but sounds much more natural than a regular T.
These pairs of words sound the same in ordinary American speech:
Examples of words where the T is usually pronounced like a D:
Sometimes the next word changes a stop T to a flap T, for example:
“What” Here, “what” ends in a stop T
“What about” Here, “what” ends in a flap T, and “about” ends in a stop T
“What about it” Here, “what” ends in a flap T, “about” ends in a flap T and “it” ends in a stop T
See if you can find the flap Ts in this text (The answers are at the bottom):
Ball Lightning, from Wikipedia:
British occultist Aleister Crowley reported witnessing what he referred to as “globular electricity” during a thunderstorm on Lake Pasquaney in New Hampshire in 1916. He was sheltered in a small cottage when he “noticed, with what I can only describe as calm amazement, that a dazzling globe of electric fire, apparently between six and twelve inches (15–30 cm) in diameter, was stationary about six inches below and to the right of my right knee. As I looked at it, it exploded with a sharp report quite impossible to confuse with the continuous turmoil of the lightning, thunder and hail, or that of the lashed water and smashed wood which was creating a pandemonium outside the cottage. I felt a very slight shock in the middle of my right hand, which was closer to the globe than any other part of my body.”
Jennison, of the Electronics Laboratory at the University of Kent, described his own observation of ball lightning:
I was seated near the front of the passenger cabin of an all-metal airliner (Eastern Airlines Flight EA 539) on a late night flight from New York to Washington. The aircraft encountered an electrical storm during which it was enveloped in a sudden bright and loud electrical discharge (0005 h EST, March 19, 1963). Some seconds after this a glowing sphere a little more than 20 cm in diameter emerged from the pilot’s cabin and passed down the aisle of the aircraft approximately 50 cm from me, maintaining the same height and course for the whole distance over which it could be observed.
Here are the words that have a flap T, in the order they appear in the text:
British, reported, electricity, cottage, noticed, what, that, 15, 30, cm, diameter, at, it, quite, that, water, creating, cottage, part
University, seated, metal, 539, Washington, 1963, little, cm, diameter, 50, cm, distance