英文關鍵字
address
alert
amp
amplifier
announce
announcement
arena
audio
background
blue
broadcast
bunch
column
commentate
communication
danger
electric
electronic
hailers
horn
information
loud
loudspeaker
mast
megaphone
music
new
old
outdoor
pair
pillar
pole
post
power
public
shout
sky
sound
soundsystem
speak
speaker
sporting
system
talk
tannoy
tree
voice
volume
warning
wire