nteger   gWasWalking;             
string    gSound = "footsteps";    
default
{
    state_entry()
    {
        
        llSetTimerEvent(0.25);
    }
    timer()
    {
        integer NowWalking = llGetAgentInfo(llGetOwner()) & AGENT_WALKING;
        if  (NowWalking != gWasWalking)        
        {
            llStopSound();
            if (NowWalking)      llLoopSound(gSound, 1.0);
        }
        gWasWalking = NowWalking;
    }
}