There is a mini-quiz at the end of the lesson. This is because the volume is slightly higher on the side closer to the object. Another factor may be that the ear furthest from the sound gets some sound reflected off objects. The brain processes this information to let you know from what direction the sound is coming. How they do that is a puzzle to me.
Indications are that it is more difficult to tell direction with low frequencies.
This is probably due to the fact that the ear is less sensitive to volume variations with low frequencies and the fact that at low frequencies the wavelength is greater than the distance between the ears. This could also muddle the sound heard. Distance detection You can detect distance from the sounds you hear, because the loudness is less and the sound is often muffled. It takes experience to be able to judge how far away sounds are coming from. Some animals such as bats and dolphins use sound to measure distance, as well as direction.