Whistle-like sounds help dolphins keep in contact and communicate with each other as they travel and feed. Dolphins listen for the strength of the rebounding clicks to identify what the object is and its distance from them. All of these clicks and whistles are created in the dolphin's nasal passages just below their blowhole. The sounds may be received by fat deposits in the lower jaw. These deposits send vibrations of the echo to the middle ear and brain for processing.
Dolphins are definitely smart but there is much debate over intelligence tests.
About 30 years ago, it was predicted that bottlenose dolphins would eventually be able to communicate with humans. This suggestion caused quite a stir and started many myths. But there has never been any scientific evidence to prove that this is possible. Nor is there any proof that dolphins are more intelligent than humans. Dolphins impress us because they swim quickly, communicate with each other, use tools and may respond to human activity.