Middle ear infections can cause a conductive hearing, a child who experiences this type of impairment is likely to have difficulty hearing:

Soft sounds

Explanation:

Conductive hearing loss occurs when the sound waves cannot be transferred in the ear due to the obstruction of any path such as the outer ear, the middle ear or the eardrum.If a person suffers from middle ear infection then the blockage would be in the middle ear and the person would suffer from conductive hearing loss.Due to this hearing loss the sound a person perceives becomes muffled and of softer due to which the sound that is already of lower frequency cannot be heard. Therefore, the child suffering from the given impairment would find it difficult to hear soft sounds.

The answer is ozone layer.