Speakers contain an electromagnet which is a coil of wire that the current flows through. First, it starts with a battery and then moves into the coil of wire. When the magnet vibrates the air molecules start moving and create waves. The waves then produce the sound that you can hear. Also there is energy transfer in a speaker. For example, the phone has electric and chemical potential energy because its a chemical reaction that causes the electricity to flow. Chemical turns into electrical and then flows through the wire. When the energy flows through the wire, it moves into a coil of wire which has a changing magnetic field because the song changes the frequency of the wire. However the magnet has a contestant magnetic field and when its placed against the coil of wires magnetic field, it allows the magnet to vibrate and in the end it makes sound.