Somebody's holding a red signal horn very close to an ear

How Loud is Loud? Protect Your Hearing!

We have often been told that very loud sounds can cause deafness. What is meant by loud sounds? How does it actually harm your hearing? What is the minimum time exposure to loud sounds that can cause deafness?

 

Loudness

Loudness may be defined as that attribute of auditory sensation that corresponds most closely to the physical measure of sound intensity and measured in decibels (dB).

A looser definition is that loudness is a psychological description of the magnitude of an auditory sensation (Fletcher & Munson, 1933). The lower the decibel (dB) value, the softer the sound is.

Ear Anatomy

Cross section of ear showing outer, inner, and middle ear structures.

This is the anatomy of the human hearing system. Sound waves enter the outer ear and travel through the external auditory canal until they reach the eardrum, causing the eardrum and the attached chain of ossicles to vibrate.

The motion of the stapes against the oval window creates waves in the fluids in the cochlea, causing the basilar membrane to move in a wavy motion.

This motion stimulates the sensory cells of the organ of Corti (in the cochlea), atop the basilar membrane, to send nerve impulses to the brain.

In simple terms, the louder the sound waves, the bigger the vibrations or pressure exerted by the auditory system. For example, in case of a bomb explosion or impulsive loud noise (more than 140 dB), the pressure will cause damage to the whole hearing system which includes the tympanic membrane, ossicles and cochlea.

This will eventually cause the sensory cells in the cochlea to be damaged. Hence, no nerve impulses can be sent to the brain anymore. In this situation, the auditory system is in dysfunction, or in other words, the ears are totally deaf or called as dead ear. The worst part is that it is irreversible! Once the sensory hair cells are damaged, they cannot be reproduced or rejuvenated.

 

Sudden loud noises are not the only way how the sensory cells can be damaged. Long exposures to certain degrees of loudness can force the sensory cells to work harder, thus become weak and eventually damaged.

The damaged sensory cells caused by long exposures to loud noise can be permanent and result to noise-induced hearing loss which affects high frequencies first. Just keep in mind that the sound level or loudness will get higher when you are nearer to the source.

This means, if you listen to songs from your headphones at a high volume continuously for long hours, you may risk getting noise-induced hearing loss.

Below are the guidelines from The Department of Occupational Safety and Health (DOSH) Malaysia and the comparative example of sounds for your reference.

82 16 hours garbage disposal machine (80 dB)
85 8 hours milling machine (85 dB), food blender (86 dB)
88 4 hours food blender (88 dB), car wash at 20 ft (89 dB)
91 2 hours motorcycle at 25 ft (90 dB)
94 1 hour power mower (95-96 dB)
97 30 minutes Boeing 737 or DC-9 aircraft at one nautical mile (6080 ft) before landing (97 dB)
100 15 minutes Bell J-2A helicopter at 100 ft (100 dB)
103 7 minutes and 30 seconds jet flyover at 1000 feet (103 dB)
107 3 minutes Jet take-off (at 305 meters)
115 28 seconds live rock music (108 - 114 dB)
ear plugs vs ear muffs

Hearing Protection

Hearing protection is very important.

The choice of hearing protection devices is a very personal one and depends on a number of factors including level of noise reduction rating (NRR), comfort, and the suitability of the hearing protection device for both the user and the environment.

Noise Reduction Rating (NRR) is a unit of measurement used to determine the effectiveness of hearing protection devices to decrease sound or noise exposure within a given working environment. The higher the NRR number, the greater the potential for noise reduction. For example, if you wear an earplug with an NRR of 29, the noise entering your ears will be reduced by 29 decibels.

For instance, there are three basic ear protection devices; earplugs, semi-insert earplugs and earmuffs. Some are available with electronic functions for more precise noise attenuation. The NRR for earplugs roughly range from 22 dB to 32 dB, and earmuffs are usually up to 37 dB. It all depends on the materials used and other built factors.

When hearing protection devices are worn in combination (i.e. earplugs AND earmuffs), the NRR are NOT simply calculated by adding the two NRR numbers together. One of the methods is simply added five more decibels of protection to the device with the higher NRR. For example, using earplugs (NRR 29) with earmuffs (NRR 27) would provide a Noise Reduction Rating of approximately 34 decibels.

In today’s gadget-dependant lifestyle, one of the common causes of people diagnosed with hearing loss is due to long exposures to loud music from headphones or earphones. Annual hearing test by audiologists or hearing care professionals is very important to monitor the changes in hearing level. Early detection of hearing loss and early intervention can prevent and slow down hearing deprivation.

In a summary; know your surrounding and always take care of your precious hearing. Avoid loud sounds or reduce the risk by wearing a hearing protection device or reduce the exposure time to loud sounds. Here at The Hearing Solution Company, we provide FREE annual hearing test, hearing aid trial and hearing consultations. Check your hearing before it is too late.

 

Reference:
1. DOSH Malaysia: https://www.dosh.gov.my/index.php/legislation/codes-of-practice/industrial-hygiene/3286-industry-code-of-practice-for-management-of-occupational-noise-exposure-and-hearing-conservation-2019/file
2. https://www.iacacoustics.com/blog-full/comparative-examples-of-noise-levels.html
3. https://www.audiologyonline.com/articles/extra-protection-wearing-earmuffs-and-1218
4. https://www.coopersafety.com/earplugs-noise-reduction