Amy is asleep. There is no noise in her bedroom. It is ______ .

Sound is an energy. There are lots of sounds all around us. Sometimes it is quiet, but often there is a lot of noise. Birds and animals make sounds. Some animals growl and others sing. We talk and laugh and shout and sing. We build machines and machines make a lot of noise. Televisions, phones and computers all make sounds. We even listen to music or play musical instruments.