The aim of any mediation is to let your body and along with your senses to a state of rest and calm.
All senses play a key role to help us reach the state of absolut calm and stillness and its not always possible without external help.
We can control sight by light or just simply closing our eyes, abd hearing can be controlled through plain silence. Smell/ scent is also an important factor to meditation. Aromatherapy or some particular aroma can prove to be useful.