I am going to answer your questions based on the assumption that you do not have US citizenship, and that you will be attending the university int he US on a student visa. if those assumptions are incorrect, then disregard.
1.) JOB - is there high demand for audio engineers in India? If there isn't, then getting an audio engineering degree in the US will not get you a good job in India. It will certainly not get you a job in the US, because you cannot work in the us unless you emigrate, and are sponsored by a US employer. There are plenty of audio engineering students in the US already, and many are struggling to find work, because this is a fairly low demand field, with a high rate of graduates. Try for electrical or structural engineering instead. Those fields have far greater demand world wide.
2.) SCHOLARSHIPS -- you can attempt to apply for scholarships on your own via scholarship websites like fastweb and scholarships.org. These are small, highly competitive, and usually not major segregated. You'll earn one or two if you are lucky, but don't count on it. If you are accepted to a university in the US, you may be given a private scholarship or grant to study there, but these are dependent on your academic performance, need, and financial availability, and are not guaranteed. You can also do dual enrollment, or apply with your own school / local government for scholarships. There may be some sponsorship programs available. Many foreign schools partner with US schools to allow their students to study abroad.
3.) PRIVATE LOANS -- because these are usually co-signed by parents, and granted in exchange for collateral, and good credit, it is unlikely that any domestic lender will be willing to give money to a foreign student. Your parents will have to look for loans on your behalf. It may be possible to secure a loan from an international lender, but that is unlikely. You'll have to do the research on these lenders with your parents.
4.) FINANCIAL AID -- financial aid that is not based on private scholarships or private loans, is sponsored by the federal government, and is only available to US citizens. As a student with a visa, you will not even be granted the opportunity to apply for this type of financial aid.
5.) JOBS -- any job, on or off campus, is barred to students with student visa status. You cannot legally work in the United States on a Student Visa.
6.) GRADES / TEST SCORES -- of course there are requirements for GRE and TOEFEL test scores. These vary from around a 1000 for less prestigious state schools, to above a 1400 for better schools. You will need to inquire about graduate acceptance requirements from every school for which you apply. There is no set minimum.
That being said, many US universities have started to open branches in India. Stanford, Harvard, and MIT all have branches in Mumbai. You can study there, and earn your degree at home. If you do, you should have no trouble getting financial aid, or having your parents take out loans. You'll also be allowed to work, and you'll have far less trouble paying for housing.