Here is a simple toggle switch that can be operated through sound signals such as whistle or clap. The output of the toggle remains either low or high until the microphone senses the next sound signal. The circuit is too sensitive and can be used to control AC loads through the relay.
The sound signal received by the condenser mic will be amplified by IC1. TL071 is the high gain Operational Amplifier used in the preamplifier section of radio and tape recorder. The amplified output is used to control the JK Flip Flop IC CD4027 designed in the toggle mode. When the clock input pin 14 of IC2 gets a low to high pulse from IC1, its output turns high and remains as such. When the next pulse arrives, the output of IC2 turns low. In this way it functions as a toggle switch. Variable resistor VR adjusts the sensitivity of MIC at the particular sound level. Relay driver T1 can be used to operate the relay.