Buzzing sound from Nissian ?

HARD TO TELL! My first guess is that your STARTER BENDIX is JAMMED to the ON position! ANYWAYS go to a DIY CAR wash with a can og GUNJK original orange and CLEAN CLEAN CLEAN everything you see! AVOID the DISTRIBUTOR is you have one but keep ENGINE RUNNING! ANY WEAKNESSES may show up here now but MOST ignitions now are SEALED and water tight! USE ONLY PENNZOIL ULTRA PLATINUM OIL in it as it extends the WARRANTY out to 500,000 MILES!  With only ONE oil change each year! ALTERNAOTR or a FAIILNF alternator BEARING maybe! ONCE the engien is CLEAN it is EASIER to tell! Of COURSE oepn the HOOD to SEE and HEAR! BYE NOW! 

Most likely a piece of metal hitting another piece of metal so it sounds like a Jew's Harp (comb and paper)  Or it is a cable or hose or something that is so close to another surface that it is in within striking distance as the engine vibrates.  It is one of those I got to stick my head under the hood and touch stuff with my hand to see if I can silence the pig.  It may be super obvious or it may be there for YEARS driving you nutso.  Some people just crank on the stereo LOUDER.

A sudden new noise is likely NOT normal.  It's your warning to investigate ASAP! 

Visit a mechanic if necessary. 

Don't get into the habit of thinking that it's ok to drive the car with a problem, just because the car keeps running.  Expensive repairs can sometimes be avoided by investigating the symptom immediately and repairing it. 

Strange noise, strange smell, strange vibration, steering pulling to one side, are all warning signs of a problem. 

Get into the habit of checking your fluid* levels REGULARLY, and walking around the car looking at the lights, especially the brake lights. 

Get an air pressure gauge to check your tires too. 

*fluids: 

Engine oil (dipstick)

Transmission fluid (if there is a dipstick) 

Coolant reservoir (check cold) 

Brake fluid in master cylinder

It is not normal.  Do a Pearl, take your car to a mechanic.

It could be many things and you've provided no useful details. Is it normal? Only an idiot would ask such a question. FAIL. Take it to a professional mechanic.

Never heard of a "Nissian".

Hey, wait...were they formally known as 'Datsoon'?

Yes, the inhabitants of planet Nissian Altima are a species of moths - and the moth men are coming - I can hear them, too.

get under the car and tap on the exhaust shields Vibrating exhaust shields are common on Asian vehicles.