Verified answer

when air is heated outside its density is decreased because the molecules that make up air become more excited. Sound is formed by pushing on these molecules which then push on others and so on as it moves.

There are certain things that will change the speed of sound including pressure and density in the air.

When air is less dense the force that is creating a sound has less resistance due to the air molecules themselves and therefore transfers its energy more quickly.

So by increasing the temperature the air becomes less dense. When the air is less dense sound can travel faster. It is governed by the following equation:

Speed of sound (m/s) = 331.5 (m/s) + 0.60T (m/[s*degC])T Where T is the temperature in degrees celsius