Hi,there is a possibility that you might have suffered from a traumatic perforation (hole) in your left ear drum.During slapping,there is sudden increase in external ear pressure which is not as same as middle ear pressure.Due to sudden change in the ear pressure ,trauma in the form of perforation (hole) in the ear drum might occur because of which you are suffering from reduced hearing. It is advisable to consult an ENT Specialist doctor to confirm the diagnosis and also a hearing test called Pure Tone Audiogram to know the degree and type of hearing loss. In case you are suffering from a traumatic perforation in ear drum,most of the Traumatic Perforations heal on there own within 6-8 weeks.You need to take precaution that no water should go inside ear while taking bath,you may use ear plug to protect your ear from water.Also don t try to clean your ear by self.Avoid listening to loud sounds. Itchiness in your throat can t be due to ear wax running down your throat.It might be due to allergy or cold.You might get relief by doing warm saline gargles and Antihistaminic tablet(like Cetrizine). Hope this answers your question.Take Care.