The exercises we use in order to sharpen our ear-perceptions and to make them serve us may be termed 'ear-training exercises.' This term may not satisfy those who delight in hair-splitting definitions; they may say, "We cannot train our ears, but we can train our capacities for using them"; but the term is sufficiently accurate to designate what we mean it to designate.
How are ear-training exercises performed? There are several varieties. The simplest of all is this: the teacher articulates various sounds, either singly or in combination with others; we listen to these sounds and make unconscious efforts to reproduce them by saying them to ourselves. This is the most passive and most natural form of ear-training; we did it years ago when lying in our cradles listening to the sounds made by the people around us. If the teacher systematizes his work, so much the easier will it be for us who are training our ears.
We must then seek to recognize or identify certain sounds and to distinguish them from others. The teacher may write (in conventional phonetic symbols) a series of sounds on the blackboard and append to each a conventional number. He will articulate a sound and ask us to give him the number pertaining to it, or we may go up to the blackboard and point to the sound we think we have heard, or he may give us 'phonetic dictation,' in which case he will articulate sounds which we must write down by means of these conventional phonetic symbols. This latter process has the advantage that it can subsequently be extended to the dictation of syllables or words.[1]
[1] It will be preferable for these to be 'nonsense words,' that is to say, artificial words with no meaning, for if real known words are articulated to us we may possibly write down not the sounds that we really hear but some sort of ingenious phonetic transliteration of the orthographic form of the word.
Other forms of ear-training exercises may be devised by those who are engaged in carrying out such work, care being taken that such exercises do really train the _ears_ and not our capacities for successful guessing.
If you wish to know to what extent such exercises do have the desired effect, go through a short course of ear-training on these lines and you will yourself be a witness to their efficacy.