▁directly ▁struck ▁id i oph one ▁per cussion ▁instrument . ▁Most ▁b ells ▁have ▁the ▁shape ▁of ▁a ▁h ollow ▁cup ▁that ▁when ▁struck ▁v ibr ates ▁in ▁a ▁single ▁strong ▁strike ▁tone , ▁with ▁its ▁sides ▁forming ▁an ▁efficient ▁reson ator . ▁The ▁strike ▁may ▁be ▁made ▁by ▁an ▁internal ▁" cla pper " ▁or ▁" uv ula ", ▁an ▁external ▁ham mer , ▁or — in ▁small ▁b ells — by ▁a ▁small ▁loose ▁sphere ▁en closed ▁within ▁the ▁body ▁of ▁the ▁bell ▁( j ing le ▁bell ). ▁ ▁B ells ▁are ▁usually ▁cast ▁from ▁bell ▁metal ▁( a ▁type ▁of ▁bronze ) ▁for ▁its ▁reson ant ▁properties , ▁but ▁can ▁also ▁be ▁made ▁from ▁other ▁hard ▁materials ; ▁this ▁depends ▁on ▁the ▁function . ▁Some ▁small ▁b ells ▁such ▁as ▁orn amental ▁b ells ▁or ▁cow ▁b ells ▁can ▁be ▁made ▁from ▁cast ▁or ▁pressed ▁metal , ▁glass ▁or ▁cer am ic , ▁but ▁large ▁b ells ▁such ▁as ▁church , ▁clock ▁and ▁tower ▁b ells ▁are ▁normally ▁cast ▁from ▁bell ▁metal . ▁ ▁B ells ▁intended ▁to ▁be ▁heard ▁over ▁a ▁wide ▁area ▁can ▁range ▁from ▁a ▁single ▁bell ▁hung ▁in ▁a ▁tur ret ▁or ▁bell - gable , ▁to ▁a ▁musical ▁ensemble ▁such ▁as ▁an ▁English ▁ring ▁of ▁b ells , ▁a ▁car illon ▁or ▁a ▁Russian ▁zv on ▁which ▁are ▁tun ed ▁to ▁a ▁common ▁scale ▁and ▁installed ▁in ▁a ▁bell ▁tower . ▁Many ▁public ▁or ▁institution al ▁buildings ▁house ▁b ells , ▁most ▁commonly ▁as