speaker = nil
speakerSide = nil
for i, side in pairs(rs.getSides()) do
  if peripheral.getType(side) == "speaker" then
    speaker = peripheral.wrap(side)
    speakerSide = side
    break
  end
end

if speaker == nil then
  print("No Speaker peripheral found")
  return
end

print("Using Speaker peripheral on "..speakerSide)
print("Press ENTER (empty line) to exit")
print("")

while true do
  line = io.read()
  if line == "" then break end
  speaker.speak(line)
end