hm... some materials are beeping, other - are not... i'd try to search solution in practical way and i'd write here, as i will get interesting results...
Quote: when does it beep and when doesn't it beep?
it may beep all time, but sometimes(using different pairs of materials) i have no sound at all
1st prize: Lite-C and Newton 2.17 by Vasilenko Vitaliy