not play sounds

i'm using the example ao_live.lua but show this error, my operating system is GNU/Linux:

$ luajit ao_live.lua

=================================================
=> type:	live
=> priority:	50
=> options:
	 - server
	 - sink
	 - dev
	 - id
	 - verbose
	 - quiet
	 - matrix
	 - debug
	 - client_namebuffer_time
=> shortName:	pulse
=> preferredByteFormat:	native
=> comment:	Outputs to the PulseAudio Sound Server
=> name:	PulseAudio Output
=================================================
=> type:	live
=> priority:	20
=> options:
	 - dsp
	 - dev
	 - id
	 - buffer_time
	 - verbose
	 - quiet
	 - matrix
	 - debug
=> shortName:	oss
=> preferredByteFormat:	native
=> comment:	Outputs audio to the Open Sound System driver.
=> name:	OSS audio driver output 
=================================================
=> type:	live
=> priority:	0
=> options:
	 - debug
	 - verbose
	 - matrix
	 - quiet
=> shortName:	null
=> preferredByteFormat:	native
=> comment:	This driver does nothing.
=> name:	Null output
=================================================
=> type:	file
=> priority:	0
=> options:
	 - matrix
	 - verbose
	 - quiet
	 - debug
=> shortName:	wav
=> preferredByteFormat:	little
=> comment:	Sends output to a .wav file
=> name:	WAV file output
=================================================
=> type:	file
=> priority:	0
=> options:
	 - byteorder
	 - matrix
	 - verbose
	 - quiet
	 - debug
=> shortName:	raw
=> preferredByteFormat:	native
=> comment:	Writes raw audio samples to a file
=> name:	RAW sample output
=================================================
=> type:	file
=> priority:	0
=> options:
	 - matrix
	 - verbose
	 - quiet
	 - debug
=> shortName:	au
=> preferredByteFormat:	big
=> comment:	Sends output to a .au file
=> name:	AU file output
=================================================
=> Device ID: 0
=================================================
luajit: ao_live.lua:32: cannot open the device
stack traceback:
	[C]: in function 'openLive'
	ao_live.lua:32: in main chunk
	[C]: at 0x5564d7c0cf40

I'm using this code:

local ao = require("ao")

-- ao.initialize()   is done automatically :-)
-- you will only need it if you have to restart the environment

-- Setup the default live driver
local default_driver = ao.defaultDriverId()
local format = { bits=16; channels=2; rate=44100; byteFormat="little"; }

local info = ao.driverInfoList()

for _,key in pairs(info) do
	print("=================================================")

	for option, value in pairs(key) do
		if option == "options" then
			print("=> "..option..":")
			for k, v in ipairs(value) do
				print("\t - "..v)
			end
		else
			print("=> "..option..":\t"..value)
		end
	end
end

print("=================================================")
print("=> Device ID: "..default_driver)
print("=================================================")

-- Open the driver
local device = ao.openLive(default_driver, format)
if not device then error("Error opening device.") end

-- Play a one second sine-wave
local freq = 440.0
local buf_size = format.bits/8 * format.channels * format.rate
local buffer = {}
for i = 0,format.rate do    -- one second
   sample = 0.75 * math.sin(2*math.pi*freq*i / format.rate)
   buffer[2*i+1] = sample   -- left
   buffer[2*i+2] = sample   -- right
end
device:play( ao.array2string(buffer) )   -- assumes 16 bits ...

-- Close and shutdown is handled by the garbage collector :-)