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.
It travel in a higher speed than sound
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".