Play some music on your phone or use a musical toy and encourage your child to try to locate the object. They may initially start by turning towards the source of the sound and you can gradually encourage movement towards the object. Use different sources of sound (wind-up toy, vibrating toy) and see if your child responds to the more muted noise than constant sound. It is best to do this in a quiet low stimulus environment so your child is not easily distracted.
Go for a walk with your child. Ask your child what different sounds they can hear. Ask them to listen to cars and point in the direction of the sound, tracking the moving sound will help them to use auditory information for orientation purposes. Encourage them to listen to the green man signal at a traffic light if available; this will help them to use sounds to orient to the environment so they understand when they hear the green man they are approaching a road. Use spatial concepts to localize the sound i.e. the traffic is behind you, the lawnmower is in front of you, etc.