In a public address system, when the microphone is placed too close to the loudspeaker, a positive feedback system is inadvertently created. The audio input from the microphone is amplified, which comes out through the loudspeaker. This audio output is received by the microphone again, which gets amplified further, and comes out through the loudspeaker again. This positive loop gain is known as audio feedback or the Larsen effect, and causes the system to overload, resulting in a high-pitched sound. Construct the corresponding feedback model, and identify each block of the model.