What are consonant sounds?

[Fazzu]

Question #: 7: They wanted to join an union, but their bosses were against it.
User's answer: True
Correct answer: False
Additional Notes: We use a before a consonant sound and an before a vowel sound. Here, the word starts with a consonant sound.

I did this English test 'Articles - A & An' and above is one the questions I did wrongly.I don't understand what is a consonant sound as I know vowels are,(a,e,i,o,u).

Could anyone please help me with it?

[rewboss]

The letter "u" is a strange letter. Sometimes it is just an ordinary vowel; but sometimes it is a vowel that begins with a consonant sound.

The consonant sound is the same as that represented by "y" in words like "you". It doesn't sound much like a consonant, but technically it is.

You do have to distinguish between vowel letters and vowel sounds. Strictly speaking, a, e, i, o and u are not vowels, they are letters which, in English, often represent vowel sounds. The letter y represents a vowel sound in "story" or "sky", but a consonant sound in "yolk". Remember that letters are not sounds, they're just little symbols.

For example, in the Welsh language, the letter w is not a consonant, it's a vowel (usually) and represents a sound similar to the English "u" in "pull". Thus the Welsh word for a valley is "cwm", pronounced "koom". In German, however, the same letter represents a consonant, a bit like English "v".

[Fazzu]

Thanks a lot!

I searched in www.dictionary.com and came across the meaning for the word 'vowel'.Here is the meaning:

A speech sound created by the relatively free passage of breath through the larynx and oral cavity, usually forming the most prominent and central sound of a syllable.
A letter, such as a, e, i, o, u, and sometimes y in the English alphabet, that represents a vowel.

For e.g, 'Honour' which is pronounced as 'onour' where the h is pronounced softly is a consonant sound?

Like they say,'an hour ago' or 'I received an hounourable gift from her'.

[Tdol]

honour- it's written with a consonant, but the 'h' is silent, so it starts with a vowel sound, the 'o'.