Scroll of silence
Reading a scroll of silence creates a radius 4 or 5 aura of silence around you, as though you had just cast the spell Silence at a spell power of 25. This prevents all things inside the aura (including you) from casting spells, reading scrolls, talking to your allies, shouting for attention, or praying. Although this disables many player abilities, it may be worth accepting that handicap to apply it to nearby enemies as well. Be aware, however, that the radius will gradually shrink (eventually only affecting you), and that all demons and some other monsters will be completely immune to the effect.
Also, enemies within a silence aura will be aware that something unnatural is going on, and they will have an easier time seeing through your Stealth.