Rain sound effect Generator

Agreeable, relaxing effect, helping to fall asleep

Small portable unit, 3V battery powered

Circuit diagram:

Rain effect Generator


R1,R2,R13______10K   1/4W Resistors
R3,R5__________33K   1/4W Resistors
R4,R6___________1M   1/4W Resistors
R7____________100R   1/4W Resistor
R8____________330K   1/4W Resistor
R9____________100K   1/4W Resistor
R10____________47R   1/4W Resistor
R11_____________1K   1/4W Resistor
R12____________15K   1/4W Resistor
R14____________47K   1/4W Resistor
R15____________10M   1/4W Resistor
R16_____________1M8  1/4W Resistor

C1,C4,C7______100µF   25V Electrolytic Capacitors
C2,C3,C6______100nF   63V Polyester or Ceramic Capacitors
C8,C10________100nF   63V Polyester or Ceramic Capacitors
C5_____________47µF   25V Electrolytic Capacitor
C9_____________10µF   63V Electrolytic Capacitor

D1___________1N4148   75V 150mA Diode

Q1___________2N3819   General-purpose N-Channel FET
Q2____________BC337   45V 800mA NPN Transistor
Q3____________BC327   45V 800mA PNP Transistor
Q4,Q5_________BC547   45V 100mA NPN Transistors

IC1___________TL062   Low current BIFET Dual Op-Amp
IC2____________4060   14 stage ripple counter and oscillator IC (See Notes)

SW1____________1 pole 3 ways Rotary Switch
SW2____________SPST  Slider Switch

SPKR___________8 Ohm Loudspeaker (40 to 85mm. diameter)

B1_____________3V Battery (two AA or AAA cells wired in series etc.)


Sound effects generators trying to imitate rain sound or sea surf are well known to hobbyists from many years: their purpose is to induce relaxation and sleep or to help in concentration and study.
The sound generated is restrained to a background level and these devices are frequently kept on the night table.
Common designs use invariably Zener diodes or reverse-biased transistors base-emitter junctions as white noise generators. The main snag of these circuits is that a supply of at least 12V is required, therefore a big battery pack or (more commonly) mains supply is used as power source.
The aim of this project was to design a small, portable unit, powered by a 3V battery and capable of shutting-down after a preset delay, in order to save power.

Circuit operation:

Two BIFET Op-Amps are used as a good, low voltage supply, very low current, white noise source. A sound resembling to a rain shower is reproduced by the speaker after being amplified by Q2.
The higher part of the white noise spectrum is attenuated by C8, slowly driven into operation by means of Fet Q1 acting as a variable resistor. Therefore, a sort of automatic tone control is obtained.
IC2 provides all the timings: it auto-resets at switch-on, shutting-down the generator after one of three time-delays, chosen by means of SW1. It provides also, through R8, slow charge and discharge of C5, in order to change smoothly high-frequency attenuation. Q3 is used as a dc switch for the generator circuit. Q4 and Q5 are its drivers.


Disclaimer: we can't claim or prove any therapeutic effectiveness for this device.