1. Field of the Invention
The present invention relates to the use of acoustic waves for charging batteries in a battery charger or in a portable telephone.
2. Description of the Related Art
Home audio systems use audio speakers to convert audio signal into acoustic waves that can be heard by a user. The audio signals are analog electronic signals that represent the time-variation of the desired acoustic waves. They generally represent music or voice signals with frequency components typically in the range of 50 Hz-20 kHz. Typically, the audio signals are received by an amplifier from a radio receiver, compact-disk player, cassette player, or other audio source, amplified to appropriate voltage and current levels, and provided to one or more audio speakers to generate the corresponding acoustic waves.
Thus, audio speakers are energy transducers that convert electrical energy into acoustic energy. The transduction from acoustic energy to electrical energy is typically performed in the speakers by providing the audio signal to a solenoid to generate a time-varying magnetic field. The time-varying magnetic field then displaces a magnetic element coupled to a speaker diaphragm, causing the speaker diaphragm to vibrate with a displacement indicated by the audio signal. With the audio speaker placed in a listening area, the vibrating speaker diaphragm generates the desired acoustic waves in the air of the listening area.
Rechargeable batteries and battery chargers for rechargeable batteries are well known in the art. The rechargeable batteries are based on a variety of electrochemical reactions, and are generally recharged by applying an appropriate potential across the rechargeable battery to run a current through the rechargeable battery. Some battery chargers monitor the energy stored in a rechargeable battery and adjust the applied potential to optimize the charging process. A main feature of battery chargers is their use of some electrical power source, such as home 120 V AC electrical power source, to drive a current through a rechargeable battery.
It would be useful to have a battery charger that does not draw current from other batteries or from a home 120 V AC electrical power source, but which instead uses an otherwise unused source of power, such as the acoustic energy generated in a room by people in the room performing typical activities such as talking, walking, and moving.