英文關鍵字
alert
amp
amplifier
announce
announcement
arena
attention
audio
blue
broadcast
bullhorn
bunch
communication
concert
danger
electric
event
hailers
inform
information
loud
loudspeaker
mast
megafon
megaphone
message
old
outdoor
pair
pillar
pole
post
power
public
shout
sky
sound
speak
speaker
system
talk
technology
tree
vintage
voice
volume
warning
white
wire
wired
wiring