Double Letters

tav	resh	peh	kaf	dalet	gimel	bet	Double Letters
/t/	/r/	/p/	/k/	/d/	/g/	/b/	IPA
תּ	רּ	פּףּ	כּךּ	דּ	גּ	בּ	With Dagesh
T	R	P	K	D	G	B	Strong (Plosive)

Th/S	-	Ph (F)	Kh	Dh	-	V	Weak (Fricative)
ת	ר	פף	כך	ד	ג	ב	Without Dagesh
/θ/ or /s/	/r/ or /ɾ/	/f/	/χ/	/ð/	/g/ /ɹ/ or /ʒ/	/v/	IPA

You can hear samples of the IPA sounds using https://www.ipachart.com/

To remember these letters, say: BiG'Dei KaPoReTh (בִּגְדֵי־כַּפֹּרֶת.) This means “covering of the mercy seat”