Noise is often an element of our environment that we take for granted. In some cases, may even intentionally abuse it, by playing our music loudly, or taking risks that otherwise we may not take if we better understood the longterm consequences. I often think that we choose to take the risks, because the consequences are delayed. Meaning, we do not face the consequences of our actions until 10-20 years later in life when our hearing begins to deteriorate. However, there are acute incidents where we may risk severe hearing loss if we are not careful. This is why noise protection and safety guidelines are very important.
NOISE REDUCTION RATING
Many safety equipment manufacturers implement the noise reduction rating on their products to help provide consumer safety. This rating is monitored by OSHA and is often used as a tool to measure safety and risk levels of noise in dB. It is a guideline only and cannot guarantee an exact reduction in a noisy environment. That is due to many circumstantial factors that are not controllable.
HOW DOES OSHA CALCULATE NRR?
OSHA has a standard formula that is used to calculate the NRR. This calculation is a time weighted average (TWA) equation where you take the dBA and subtract 7 and x it by 50%. That will give you the NRR.
STANDARD THRESHOLD SHIFT
The standard threshold shift is known in the occupation safety field as a change in the hearing threshold of an employee's baseline hearing. The average loss is of 10dB or more at 2000, 3000, and 4000 hertz. This is an important element to address and be mindful of, because this directly correlates to the ability (or inability) for communication. This hearing loss occurs in the frequencies where humans speak and hear and are essential for communication.
5dB EXCHANGE RATE
This is a ratio where for every 5dB increase, a person's duration of exposure is cut in half. This is allows for a better baseline on permissible exposure limits and how to regulate the safety of the workers in the company. Keeping in mind, this exposure is constant without pause. For example, in an 8 hour time period, exposure can be around 90 dBA. If the dBA increased to 95, the exposure (cut in half) would then be only 4 hours. If it increased to 100dBA, the maximum allowable exposure time is then cut to 2 hours.
ADVERSE HEALTH EFFECTS FROM HIGH NOISE ENVIRONMENTS
The above sound meter photos are measurements taken during different environments. The top dB reading was taken in a short-burst time where the lawn mowers were passing by the house. It fluctuated from 101 dB to 70 dB. I never realized just how loud a lawn mower was until I saw this reading on the meter. I couldn't believe that I had never worn ear protection before when being around lawn mowers even for a short period of time. This information will actually change how I view my hearing protection and will view it more importantly.
The below meter was taken in the living room with 2 windows open on the first floor. The ambient outdoor sounds and no TV on ranged between 48dB-56dB.
