Noise Exposure and Hearing Loss - Defining Harmful Noise

Noise Exposure and Hearing Loss – Defining Harmful Noise

The 5 senses: taste, touch, smell, vision, and hearing… it is through these 5 senses that we experience life. It’s feeling the sun’s warmth on your skin, or the smell of rain on fresh-cut grass, or hearing the birds chirping in the trees. These experiences make life feel rich, full, and precious. If you are reading this article, it is likely you take great pride in your home, lawn, or projects in general. The tools required for these jobs can be quite loud and noisy. Preventing this noise from doing damage to our ears and thus preventing the dulling of our sense of hearing is a key aspect to preserving the full human experience!

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How Do We Know We’re Not Damaging Our Hearing?

First things first- There are two variables involved in dangerous noise:

  • Loudness, and
  • Duration.

A loud noise for a few short seconds may be harmless. A more moderate noise for a few hours can be damaging. By the end of this short read, you will feel confident you can move forward with all your projects in a safe, ear-friendly manner.

Mowing with Hearing Protection

Loudness is measured in a unit called “decibels”, abbreviated as dB. In the same way that we measure food in ounces, but our own bodies in pounds… Decibels can also be measured by different scales. There’s the dB(A) scale, the dB SPL scale, and the dB HL scale, to name a few! When we choose to measure sound in one of these scales, we are “weighting” the sound in different ways.

To understand weighting, we must first understand the basics of frequencies.

Explaining Sound Frequencies (and why they matter)

Sound, as we perceive it, is essentially the vibration of the air particles all around us. When an object produces a sound, that object is essentially vibrating very slightly in space. The vibration of the object “bumps into” and displaces the air molecules surrounding that object. Those molecules that were just displaced will then “bump into” their neighboring air molecules, and so on! This creates a wave of energy that travels through the air until it reaches our ears.

These waves are gathered up by our outer ear (the part we can see, called the pinna), and then funneled down the ear canal towards our incredibly sensitive ear drums. The ear drum can “feel” or “detect” these waves. This is the first step in the hearing process, and its function triggers a chain reaction that eventually leads to us perceiving sound!

Now, the ear drum is only sensitive to a certain range of frequencies. Essentially, if the object making a noise vibrates too quickly or too slowly, our ears will not detect the noise being generated by that object’s vibration. This rate of vibration is what determines the frequencies that object’s sound produces. When measuring noise, scientists have established a weighting scale that only considers the frequencies the human ear can perceive. This is referred to as “A-weighting”.

All measures of sound we discuss from this point forward will be listed in dB(A) weighting as a result. This will be important when we learn together how to measure the noise of our lawn equipment, power tools, and more!

About the Sound Produced by Lawn & Landscaping Equipment

On average …

Gas Powered Riding Mower Produces 95 dB(A) of Noise

A gas-powered riding lawnmower with the blades turning at full throttle will produce a near-steady 95 dB(A) of noise.

Gas Powered Push Mower Produces 85-90 dB(A) of Noise

A smaller gas-powered push mower will produce closer to 85-90 dB(A) of noise.

There are variations to these levels depending on your specific equipment, but the level at which noise can become harmful to our ears is 85 dB(A).

Now, these estimates are great, but let’s get a little more “measured” in our approach!

How to Estimate Your Equipment’s Noise Output

Now that we understand what constitutes harmful noise, let’s get a little more measured in our approach to protecting our hearing.

NIOSH, or the National Institute of Occupational Safety and Health, is a U.S. organization that, through study and research, developed a great sound level meter that is free to use in the form of a smart phone app.

NIOSH Sound Level Meter App - Available on the CDC Website

In the “app store”, simply search the words, “NIOSH Sound Level Meter”, and install the app! If needed, you can also use the search engine on your smart phone to find it; Just make sure you’re on the CDC’s website before installing!

It’s worth briefly noting that this app is not perfect! If your smart phone’s microphone is plugged up with lint or dust, your measurements can be affected.

Despite this, it remains a great tool to get a rough estimate of noise levels, and I encourage all to give it a try!

How to Use This Free App to Estimate the Decibel Output of Your Mower

Upon opening the app and reading through the disclaimers and words from the developer (the CDC), you’ll find yourself looking at this screen, pictured below:

Sound Level Meter Screenshot - Instantaneous dB(A) Level Reading

By default, the weighting or scale is correctly set to dB(A), which is perfect for our needs. An instantaneous reading will be shown at the top. This reading of 37.5 dB(A) reflects a very quiet room without the furnace running.

The simplest way to estimate your equipment’s noise level is to fire up your equipment, open your app, and take note of the instantaneous noise levels displayed on your phone’s screen. This number will bounce around quite a bit… but over the course of 20 to 30 seconds, you should have a rough estimate of that equipment’s noise output. As a general, very safe rule… if the noise is hovering at or around 85 dB(A) or more, hearing protection can save your ears from potential damage!

Now, let’s take things to the next level.

Getting More Precise Data

Referring to the screenshot pictured here, if we press the blue, circular button with the “Play” triangle in the center, we’ll see several new measurements begin to populate.

Sound Level Meter Screenshot - Recorded dB(A) Level Reading

By pressing this “Play” button, the app will begin recording noise levels over time. In this screenshot, one minute’s worth of noise has been recorded, as seen in the “total run time” measure at the top. Note that pressing the “Pause” button to the right of the play button will stop the recording.

Below you’ll find an explanation of each applicable metric being measured:

  • Instantaneous Level – The current noise level measured at any given moment.
  • LAeq – The AVERAGE noise level over the duration of the recording.
  • Lmax – The loudest sound measured throughout the duration of recording.
  • LCpeak – The loudest sound measured using a C-weighted scale (Note: since this is not weighted in dB(A), this measure can be largely ignored).

To be as precise as possible when measuring the noise levels of your equipment, I recommend the following method:

  1. Start your equipment, throttled up to the level you would typically use. (If on a lawnmower, safely start the blades)
  2. Press the “Play” button on the app.
  3. Record for 60 seconds or more, then press “Pause”.
  4. Turn off your equipment and take note of the LAeq measure of average noise level.
  5. Use this LAeq measure to determine the need for hearing protection per the reference above!

Concluding Thoughts

And just like that, you’ve changed the question of, “Do I need to wear hearing protection?” from a game of estimations and guessing into a measured, precise, and reliable method that can be applied to any noisy situation you encounter in life.

Now You Know How To Check Your Mower's Decibel Level with Your Smartphone

Hearing loss from loud noise usually happens very slowly over many years. Noise exposure in our youth affects our likelihood of hearing loss as we age. Hearing damage already sustained can always be made worse by continued loud noise exposure.

But you, dear reader, are already taking steps to prevent hearing loss’s insidious onset! This proactive, preventative approach will serve you well not only with your ears, but in all aspects of life! As an audiologist, it brings me great joy to know there are people out there seeking better ways to take care of their hearing. If your sense of hearing is dulled – life is dulled! Let’s keep our ears as sharp as possible for years to come.

Stay tuned for my next article… all about selecting and using hearing protection effectively!


Dr. Ryan Leahy is the owner of Leahy Audiology and Hearing Aids, a private practice located in Frankfort, Indiana. Dr. Leahy attended Purdue University for his undergraduate education before earning his doctorate from Indiana University in July of 2020. He practiced audiology for three years in Lafayette, IN before opening his own clinic in October 2023 with a simple mission: To empower people to make informed decisions about their hearing through direct, honest, evidence-based communication. His written articles have been published online and in local magazines and periodicals across central Indiana.

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