sound is music
Yes. The word "useful" has the long (yoo) sound.
You would use "a" before "useful" when it is followed by a consonant sound. For example, "a useful tool." You would use "an" before "useful" when it is followed by a vowel sound. For example, "an useful addition."
Useful: Energy Light Sound Non-Useful: Electricity C02
Sound advice is advice that is very useful and wise.
boat
A lubricant and sound insulation.
they help healing
Well, in our era of digital sound phonograph is a great choice to hear real analog sound :)
As long as it is not used manually in a destructive manner
A knowledge of physical sciences would be useful to a musician because they would have a better understanding of sound waves and sound properties. It would be useful to photographers so that they could understand light and the bending of light.
Typically in American English the statement would be "a cow is a useful animal" - the first sound in useful is close enough to a consonant that most individuals will use "a" rather than "an".
It travel in a higher speed than sound