Learn Spanish (Latin America): Este bullicio constante es tan sofocante y desesperante que quiero llorar. - This constant bustle is so suffocating and infuriating that I want to cry.

We use tan because it is modifying the adjectives sofocante and desesperante. Tan means "so" and is used before adjectives and adverbs. You would use tanto (or tanta, tantos, tantas) before a noun to mean "so much" or "so many" (for example, tanto bullicio meaning "so much bustle").

There are two adjectives here. Do I need to repeat tan and say tan sofocante y tan desesperante?

No, you don't have to repeat it. A single tan covers both adjectives when they are connected by y (and), just like in English ("so suffocating and infuriating"). You could repeat it for extra dramatic emphasis, but it is not required.

Desesperante is translated as "infuriating", but doesn't the root word desesperar mean "to despair"?

Yes, but desesperar has two main meanings: "to lose hope" (to despair) and "to exasperate or drive someone crazy." As an adjective, desesperante usually takes on the second meaning, describing something that makes you lose your patience completely—meaning "infuriating," "exasperating," or "maddening."

What is the difference between bullicio and ruido?

Ruido is the general word for any kind of "noise." Bullicio specifically refers to "bustle," "hubbub," or "racket"—the chaotic, lively, and overlapping noise made by a crowd of people talking, laughing, and moving around.