Speaker V2
The micro:bit V2 has a built-in speaker located on the rear of the board.

By default sound output will be via the edge connector on pin 0 and the built-in speaker V2. You can connect wired headphones or a speaker to pin 0 and GND on the edge connector to hear the sounds.
The speaker can be turned off or on using the functions listed here.
Functions
- microbit.speaker.off()
Use
off()
to turn off the speaker. This does not disable sound output to an edge connector pin.
- microbit.speaker.on()
Use
on()
to turn on the speaker.
Example
An example that runs through some of the functions of the speaker API.
from microbit import *
# Check that the speaker is on
print(speaker.is_on())
# Play a sound
audio.play(Sound.HELLO)
sleep(2000)
# Disable the speaker
speaker.off()
# Check that the speaker is off
print(speaker.is_on())
# Play a sound. This will not be heard on the speaker, but will be heard
# on Pin 0 if you have headphones or a speaker connected.
audio.play(Sound.HELLO)