Definitely sounds like an exhaust leak. The question is, from where? With the engine running, and parked with the brake on, walk around the car, and try to pinpoint the location of the noise. You'll most likely have to crawl down around the car. To give you an idea of what to look for, it will most likely be in the exhaust pipe running from the engine to the tail pipe at the rear of the car. This car has a flex pipe that is located under the engine. Then the first muffler looking thing is the catalytic converter. Be very careful, this thing gets extremely hot. It will next go through the connecting pipe to the muffler. Then from the muffler to the tail pipe. The flex pipe is a bit pricey, but the catalytic converter is the most expensive, about $200. The other pipes are cheap and easy, and a muffler shop will repair these quickly. The muffler isalso cheap. We had to replace the connecting pipe, muffler and tail pipe for my wife's car, and total price was about $150 with a 1 year warranty.