How to mix two signals without changing the overall loudness?

1. How do you mix two audio signals?
2. Can we add two signals?

How do you mix two audio signals?

Step 2: Mixing the Signals

The easiest way to do this is to combine them together using resistors. If you connect each respective left channels to a 1K resistor, and the other end of each resistor together, then you have effectively mixed the left channels together. The right channels can be mixed in identical fashion.

Can we add two signals?

Signal addition—Two signals x(t) and y(t) are added to obtain their sum z(t). An adder is used. Constant multiplication—A signal x(t) is multiplied by a constant α. A constant multiplier is used.