How Does Noise Injure Your Hearing?

Hearing loss happens when your a part of your ear or its nerves stops working as it should. There are times when the damage is irreparable.

Loud noise, either through single or repeated exposure, damages the cells and membranes in your cochlea.

Noise may damage your auditory nerve, making it challenging to discern speech in noisy environments.

An average person has approximately sixteen thousand hair cells inside their cochlea. This hair carries sound to the brain, which is how we hear.

High noise levels produce intense vibrations, forcing the stereocilia against the membranes and breaking them. When they break, outer hair cells swell, and sound cannot reach the brain normally.

Between 30 and 50 percent of your hair cells need to be damaged before noticing the hearing loss. Unfortunately, by the time you detect hearing loss, you cannot undo it.

Your Hearing Protection Dictionary

Here are some helpful terms you will encounter when selecting suitable devices.

Attenuation Value

This value represents the decrease in sound level experience by a wearer with a hearing protection device in place.

F-MIRE

This describes a method of field-testing hearing protection’s attenuation.
F-Mire stands for Field Microphone-In-Real-Ear.

It is the preferred test offering a good balance between speed, accuracy, repeatability, and correspondence with actual practice.

PAR – Personal Attenuation Value

Attenuation refers to the decrease in sound level in a wearer’s ears while wearing hearing protection. The PAR is a calculated value of a probed insert in each ear during a hearing protector fit test.

It gives a rating of the fit of a specific product for a particular wearer. PAR can either be measured through a single fit or as an average of multiple fits.

Decibel

A decibel is a unit measuring the intensity of a sound. Sound levels described as decibels must have a reference indicated. For example, decibels Sound Pressure Level (dB SPL).

NRR – Noise Reduction Rating

This is the single-number description of a hearing protector’s noise reduction capability tested under standardized laboratory conditions.

NRR is the rating system used in the US.

SNR – Single Number Rating

This is a similar measurement to the NRR. However, it is used in Europe and other regions and is determined using a different method and calculation.

SNR values tend to be a few decibels higher than NRR values.

Frequency

This is the measurement of the number of sound vibrations in one second. A frequency measurement establishes the levels of intensity of specific tones.

Noise

Noise is an unwanted or complex sound with irregular vibrations and no pitch.

Sound Pressure

This describes the pressure variations in the air created by sound waves.

How Noise Ratings Work in Different Regions

When you purchase hearing protection, it’s essential to ensure it sufficiently reduces noise for your specific environment. Long-term exposure to noise above 70dB or single exposure to noise above 120dB will damage your hearing. Your hearing protection must reduce noise levels to below 85dB.

Each hearing protection device has a rating that indicates the noise reduction level it offers. However, this rating differs between geographic regions.

NRR: United States Noise Rating

In the United States, they use a Noise Reduction Rating (NRR). The NRR tells you how many decibels it reduces noise by. On the other hand, European standard is referred to as Single Number Rating (SNR). In South Africa, we use SNR hearing protection ratings. However, to understand the calculations of SNR, we must first look at NRR.

“How-to” for NRR-devices

Measure noise intensity in your workplace with a Sound Pressure Level meter with an A-weighted filter. Take an average measurement of the noisiest area.

To determine if hearing protection is appropriate, you subtract seven from the NRR. Once you have this value, you subtract this from the average noise measurement. The resulting number is the actual noise level heard by the wearer.

However, this is only the case under ideal circumstances. In the United States, OSHA assumes that hearing protection will not be correctly fitted or worn by trained users. To account for this, they apply a 50 percent correction factor.

To calculate the actual exposure level according to OSHA, you subtract seven from the NRR. Once you have this value, divide it by two and continue with the calculation.

OSHA assumes that noise exposure is worse than what you have calculated to ensure appropriate protection.

SNR: European Union & South African Noise Rating

Unlike American standards, the European Union regulations assume that wearers are fitted and trained to wear hearing protection.

European hearing protection has a Single Number Rating (SNR) instead of an NRR.

“How-to” for SNR-devices

To determine appropriate safety, measure noise intensity in your workplace using a C-weighted filter.

You deduct the SNR from the noise level rating, and the resulting figure is the assumed noise level heard.

3M Noise Rating

3M does not believe in reducing noise level ratings to account for ill-fit or poor training.

They created the E-A-Rfit Dual-Ear Validation system to ensure their devices fit perfectly for maximum protection.

What is Fit Testing?

Fit testing measures the actual noise reduction experienced by a specific wearer. This noise reduction is a Personal Attenuation Rating (PAR).

Fit-testing occurs through various methods, with F-MIRE being the preferred.

What Makes 3M’s Fit Testing Unique?

The 3M E-A-Rfit Dual-Ear Validation system consists of a loudspeaker that generates random high noise levels. The test subject sits with their nose 30 centimetres from the loudspeaker. A dual-element microphone measures noise levels outside and inside the ear canal.

These specially designed microphones connect to a specially modified 3M probed hearing protector. The 3M E-A-Rfit Dual-Ear Validation system provides earplugs and earmuff testing.

Testing both ears simultaneously saves time. It measures a staff member’s PAR in less than five seconds. Fit testing should accompany training in the correct use of hearing protection to be accurate.

You can save each staff member’s fit test results to their file for record keeping purposes. Consistent fit testing helps you identify if a staff member is experiencing hearing difficulties. Having a record of previous fit tests helps you to assess whether their hearing loss is noise-induced. A staff member who has consistently achieved an adequate fit test result is unlikely to have noise-induced loss.

The 3M E-A-Rfit Dual-Ear Validation system identifies workers at high risk of noise-induced hearing loss. It also enables you to train and motivate your staff on the correct use and fit of hearing protection.

This fit-testing method is unique because it tests more than just the seal factor of the hearing protection. Our 3M system exceeds market requirements for fit-testing equipment by checking all hearing protection factors.

3M Hearing Protection Technology

3M invests a lot of time and effort into creating a variety of top-quality hearing protection. They cater to every employee and application with several types and sizes of earplugs and earmuffs.

Their product design values comfortable and extended wear to provide your team with convenient and wearable protection.

Hear for Life with 3M and Delta Health and Safety

Delta Health and Safety and 3M care about your hearing protection. We are here to support your needs with fit-testing and appropriate training.

Contact us for any hearing protection needs and advice.