Understanding Noise Safety: How Does Noise Damage Hearing?

The QuietBench blog often focuses on lab safety and the importance of reducing noise in your lab. But have you given any thought to exactly how noise damages your hearing? We thought it might be good to take a step back from our noise safety posts about decibels and the difference between sound and noise to talk about the mechanics of hearing and how dedicated lab furniture can help preserve it.

A Primer on Hearing and the Ear

To understand noise safety, we need to understand the ear. Like many systems in the human body, the ear is an incredibly complex and delicate instrument with multiple subsystems. To understand how these systems function, let’s follow a sound wave as it travels through the three parts of the ear.

The Outer Ear

Sound enters our body through our outer ear, which includes the pinna, which is the external part of the ear. It is shaped to collect and funnel sound waves into the narrow passage called the ear canal, which leads to the eardrum at the back of the outer ear. The ear canal and eardrum can be accessed and damaged by external forces, such as cotton swabs, but are seldom damaged by noise itself.

The Middle Ear

The eardrum vibrates as a sound wave hits it, sending vibrations into three tiny bones located in the middle portion of the ear. These bones, called the malleus, incus, and stapes, serve the function of coupling air vibrations with fluid vibrations in the cochlea, which is in the inner ear.

The Inner Ear

The inner ear is where the magic happens and where the ear is most susceptible to noise-induced damage. The cochlea has two portions, an upper and a lower, with an elastic partition, called the basilar membrane, separating the two. When the bones in the middle ear set the cochlear fluid to vibrating, a wave forms along that basilar membrane.

The basilar membrane is covered with tiny hairs, which ride that wave — much like seaweed in an ocean current. At the top of each tiny hair is a microscopic projection, called a stereocilium. When the wave moves the basilar membrane, these stereocilia bump against an overhead structure and bend. That bending action causes pore-type channels to open. Chemicals then rush into the cell at the top of the stereocilia.

That chemical reaction causes an electrical signal, which is transmitted to the brain through the auditory nerve. The brain completes the process by translating that electrical signal into a sound that the mind can recognize and interpret.

Noise Safety and the Inner Ear

Most noise-induced hearing loss is caused by the damage and death of those inner ear hair cells and stereocilia. There are exceptions, such as the bursting of the eardrum or damage to the three bones in the middle ear, which can be caused by extremely sudden and loud noises, such as explosions.

While it’s unlikely a lab will exceed the threshold of 85dB of noise per 8-hour shift that regulations have set, it’s still important to be careful. After all, when those inner ear hairs and stereocilia are damaged and die, they do not grow back. (This is one way in which we are different from birds and amphibians whose hair cells do regenerate.)

Make Lab Safety a Priority with Dedicated Lab Furniture

The need to reduce noise and protect hearing is why we promote our dedicated lab furniture as a key component in your lab safety program. Our IonBench MS decreases the impact of mass spec vacuum pump noise by 75%, saving countless inner ear hair cells from a premature death. To learn more about how our IonBenches can promote noise safety in the lab, contact Tim Hawkins today at 1-888-669-1233 or by email.