My late father was troubled by hearing loss as he got older. I would often have to repeat myself, and sometimes he could only understand me if I spoke in Ilocano with a low voice.  Other times, we would joke that he had "selective hearing loss," choosing to only hear things that he wanted to hear.

To understand what causes hearing loss, let's review the parts of the ear. The ear has three main parts: the outer, middle and inner ear. As sound waves pass into the outer ear, this causes the eardrum to vibrate. The middle ear contains the eardrum and three small bones that transfer the vibrations to fluid in a snail-shaped part of the inner ear known as the cochlea. The cochlea has nerves cell and thousands of tiny hairs that help turn the vibrations into electrical signals which are transmitted to the brain, that then turns these signals into what we perceive as sound.

There are three types of hearing loss:

Conductive, involving the outer or middle ear. This can happen with buildup of earwax that can block soundwaves from passing to the middle ear.  The eardrum can rupture with sudden changes in pressure, loud blasts of noise or by poking the eardrum with an object. Repeated ear infections and unusual bone growths and tumors around the ear canal can also cause hearing loss.

Sensorineural, which involving the inner ear. This can happen with aging and as loud noises damage the hairs or nerve cells in the cochlea.

Mixed, which is a combination of the two.

Age-related hearing loss, also known as presbycusis, happens gradually and typically involves difficulty hearing high-frequency sounds. 

Being around loud noises over time can also increase your risk for hearing loss. Jobs with constant loud noise, such as construction or factory work, can lead to damage inside the ear. Other activities with dangerously high noise levels include motorcycling or listening to loud music.