Someone who studies flags is called a Vexillologist
Someone who studies languages is usually known as a linguist.
someone who studies insects is an entomologist and one who studies spiders is an arachnologist
You call a person who studies butterflies and moths lepidopterist
a person who studies planets is a planetologist.
A scientist is someone who studies science.
someone who studies sound and it's properties is a Audiologist
There is no special name for someone who studies Hebrew.