Phone screening from HR and hiring manager, and then a 7 hour day long interview among the whole department with questions about experience and "thought experiments" asking me to think critically through a certain math/physics problem

One phone interview, along with an onsite interview. For an entry to junior level position, expect to be tested on everything from electroacoustic transducers in ported enclosures (speakers and microphones) to signal processing. Make sure you're passionate about what you're interviewing for.