alert

amp

amplification

amplifier

announce

announcement

audio

background

blue

broadcast

bullhorn

commentate

communication

concert

cone

danger

electric

emit

hailers

horn

information

loud

loudspeaker

megafon

megaphone

music

old

outdoor

pair

pole

post

power

public

shout

sky

sound

soundsystem

speak

speaker

sporting

system

talk

technology

tree

trio

trumpet

voice

volume

warning

wire

wiring