I read in 2004 of a French businessman who wanted to learn better English because of the demands of his work. He made a considerable effort, but with very small success. He went to his doctor who referred him for tests on his hearing. It turned out that his effective hearing range in terms of sound frequencies was quite limited. Then he recruited some French University researchers, who found that average French speech uses a surprisingly limited frequency range, while average English speech uses much more, especially in higher frequencies. There was also considerable variation in other languages they investigated. They have created some software to train people’s ears when they want to learn another language. It is hard to use or make a sound-difference which you cannot hear. And it can be hard to learn to hear it in the first place.
