Electrical noise generation circuits for use in conjunction with an electro-acoustic transducer to simulate the sound of burning wood sounds

A method of generating audible sounds simulating burning wood log sounds, comprising the steps of:

• amplifying low level electrical noise signals to produce a stream of randomly occurring noise signals;
• generating randomly occurring substantially unipolar signal components of said stream of noise signals within a selected, narrow audio-frequency band;
• and
• using said substantially unipolar signal components to drive an electro-acoustic transducer to produce a randomly occurring sequence of sounds approximating sounds of burning wood logs.

Apparatus for simulating sounds produced by burning natural wood logs, suitable for use as an accessory to an artificial wood log fireplace, including a random noise generating circuit comprising:

• a wide band, small signal amplifier having an input circuit including a wide band solid state electrical noise source;
• a frequency selective amplifier coupled to a signal output of said small signal amplifier, said frequency selective amplifier including a negative feedback loop determining a narrow frequency pass band of output signals from said frequency selective amplifier, said narrow frequency band centered on a frequency in the range of about 2,000 Hz to 4,000 Hz and defined by a frequency response characteristic having 10 db points spaced apart by about 250 to 550 Hz;
• a signal rectifier circuit having an input coupled to a signal output of said frequency selective amplifier and an output coupled to an input of a power amplifier;
• and
• an electro-acoustic transducer having a drive input coupled to an output of said power amplifier.

Apparatus for simulating sounds produced by burning natural wood logs, suitable for use as an accessory to an artificial wood log fireplace, including a random noise generating circuit comprising:

• a) a wide band, small signal input amplifier having an input circuit including a zener diode providing a wide band solid state electrical noise source;
• b) a frequency selective amplifier coupled to a signal output of said small signal amplifier, said frequency selective amplifier including a negative feedback loop including a band pass filter determining a narrow frequency pass band of output signals from said frequency selective amplifier, said narrow frequency band centered on a frequency in the range of about 2,000 Hz to 4,000 Hz;
• c) a signal rectifier and amplification circuit having an input coupled to a signal output of said frequency selective amplifier, and an output coupled to supply randomly occurring, substantially unipolar signals to an input of a power amplifier;
• d) said input amplifier, frequency selective amplifier, signal rectifier and amplification circuit, and power amplifier interconnected with each other on a printed circuit card;
• and
• a low voltage d.c. power source for powering said random noise generating circuit;
• and
• an electro-acoustic transducer having a drive input coupled to an output of said power amplifier, said electro-acoustic transducer, printed circuit card and power source all contained in a common enclosure to provide a self-contained unit.