The /t/ and /d/ sounds are produced in a similar manner. The /t/ sound is made by putting the tip of your tongue on the little behind your top front teeth. Your air is temporarily stopped by your tongue in this position. Next, quickly release the tongue, allowing air to rush through your mouth.
The /t/ sound is unvoiced, which means that means that your vocal cords do not vibrate/your voice is turned off.
The /t/ sound is unvoiced, which means that means that your vocal cords do not vibrate/your voice is turned off.