This is where cat raises its tail, backs up to some vertical surface or vertically-oriented object and shoots urine strait or almost strait back. This is most commonly associated with urine marking, a predominantly male behavior primarily driven by testosterone. This is what is known as a learned behavior. In the last few years I have discovered an interesting phenomena. Distinguishing between such factors is essential to accurately diagnosing problems, and this is the key to making appropriate treatment recommendations.
Cat play is almost always silent.
I suspect, from the information you provided, that Sandy has a mild aversion to some aspect of the litter box, and you may have some mild territorial disputes developing as well. To fully assess the problem and provide an effective treatment plan, a consultation would be warranted.