Power tools are simply awesome. However, with their power comes also responsibility—leaf blowers are no exception. Even though they are possibly the safest power tool out there, compared to chainsaws, hedge cutters, etc., leaf blowers can still be dangerous if mishandled.
This article will focus on one of the hazards that arise when dealing with blowers—noise, and how to deal with it. More specifically, we will be talking about hearing protection.
We urge you not to treat the issue of noise likely and let us explain why hearing protection is absolutely crucial to ensure safe leaf blower use.
Why wear hearing protection?
While it is common knowledge, that loud sounds such as gunshots or fireworks can cause instantaneous damage to your ears, that may even result in permanent hearing damage, few people consider the more insidious, chronic hearing damage.
If you’ve ever been to a gun range, or watched Private Ryan, you will note that it is obvious when instantaneous hearing damage, often dubbed acoustic trauma, takes place—you hear ringing in your ears, all sounds suddenly fade away and in many cases your ears hurt, or even bleed.
However, you will most likely never notice when you are chronically damaging your ears. In many cases, the sound levels in play do not sound particularly loud. This, of course, makes them even more dangerous.
Power tools, such as leaf blowers, are some of the loudest devices in your house and thus, to prevent chronic hearing damage, it is necessary to use adequate means of hearing protection during their use.
Why is hearing protection important?
In simple terms, you should wear ear protectors to protect your hearing.
However, for the curious readers out there, it may be useful to explain how hearing damage occurs.
What we call sound, or noise, are mechanical vibrations, or technically more correctly, waves. The amplitude of the wave, or its height, corresponds to the loudness of the sound and the wavelength, or frequency, to its pitch. This is easily imagined when one has experience with hitting metal objects, or better yet, musical instruments, which upon impact start to vibrate and emit noise.
The vibrations of the object cause in turn vibrations in the surrounding air, which is a good mediator, since it is a gas. The wave then propagates through space, all the way into your ear canal.
Since there have been entire books written on the topic of hearing, and we are limited to the length of a humble article, we will shorten the explanation to the fact that your ear drum is literally impacted by the wave and the sound is transferred into your inner ear, from where a signal is carried to your brain.
Since the ear drum functions as described above—like a drum, it is not hard to imagine that hitting it too hard for too long may permanently damage it. This is where protection must be applied.
Hearing protection serves to reduce the impact of the incoming sound by various mechanisms, described further in this article.
When should hearing protection be worn?
Hearing protection should be worn whenever the user may find himself confronting a hazard of suffering hearing damage. This in turn can result in noise-induced hearing loss, or NIHL in short.
While it is hard to draw an exact line as to what is or isn’t loud enough to cause hearing impairment, a good rule of thumb is that hearing protection is necessary above 80 dB, but highly recommended when using any power tool regardless of its noise rating.
In other words, better safe than sorry. After all, you only have one pair of ears, and once they’re gone…
How are hearing protectors rated?
Northern American products are rated by the noise reduction rating standard, or NRR in short—a single number, which characterizes the quality of the hearing protection device. However, as with many ratings, to deduce what the number means is somewhat challenging.
The NRR characterizes the number of decibels by which the original noise is reduced. However, even though the NRR is often listed with the dB unit, you cannot simply subtract the NRR from the noise directly.
Here is the correct approach
- We must first subtract 7 from the NRR.
- (Optional but recommended) The result of the subtraction is then divided by 2—this is an effectiveness correction, which will be explained further below.
- This is the number by which the original noise is reduced.
We provide a calculated example for NRR 30 earplugs blocking 100 dB noise.
Note that a somewhat typical ear protection rating of 30 is not enough to reduce the sound of a 100 dB leaf blower, of which there are a few, to the 80 dB threshold.
The SNR, an EU equivalent of the NNR, is rather straight forward and allows direct subtraction from the original noise.
However, both above-mentioned numbers are a mean, derived from testing noise reduction at multiple frequencies. The actual noise reduction will therefore depend on the frequency of the noise, but also, and possibly more importantly, the correct fit of the protection and its durability. This may result in an up to a 50% loss of effectiveness, which is accounted for in the example above.
What is active hearing protection?
Active hearing protection, or active noise cancellation is a fancy name for a rather modern, but not exactly sophisticated technology which blocks selectively frequencies which are typical for noise. You may have even encountered the principle behind the technology in your high school math or physics class—wave addition.
Simply put, when adding two waves, such as sound waves, you may achieve two extreme results based on their phase difference. The first being a wave with amplitude (height) that is exactly the addition of each of the two waves’ amplitude, the second being an exact subtraction.
Active hearing protection does exactly that. By emitting an opposing sound wave, it subtracts the height of the “noisy” waves.
Active noise cancellation can be found in some ear muffs. While it is mostly used in aviation, it often founds use in other fields, including landscaping.
What is passive hearing protection?
Passive hearing protection is the most basic and common type of ear protection available on the market.
Passive hearing protection mechanically blocks the path of the incoming sound waves into your ear canal. A basic example would be simply plugging your ears with your fingers. Thus, the sound waves are no longer propagated by air, but by the hearing protection, such as tips of your fingers.
Since your fingers are a tougher medium than the air—they are harder to vibrate around than the free and mobile molecules of air—the energy of the wave is greatly reduced, which results in reduction of perceived noise and hearing damage.
By comparing the mechanism of active and passive hearing protection, we can easily deduce that the advantage of the former is its ability to only block out the damaging noises, while passive protection blocks out all noise indiscriminately.
What are the different types of hearing protection?
The most common and easy to use hearing protection are ear muffs. While they often look far from fancy, they do their job. Their effectiveness, of course, depends on the correct fit. It is recommended to use adjustable earmuffs, since one size simply does not fit all.
Earmuffs come in various designs. The most common ones feature one strap only, which is fitted over the user’s head. Advanced models have a second supporting strap, which is fitted around the back of the user’s head. Earmuffs should be worn directly over the head, without a hat, unless they are designed for this specific purpose.
Ear plugs are a cosmetically and often even functionally advantageous alternative to the afore mentioned earmuffs.
An earplug is made of moldable material, which is squeezed and inserted into the ear, where it is left to expand. This way, the ear canal is filled with the protective material.
While they are cheaper and often more effective than earmuffs, they may be harder to use correctly. For many, they are also less comfortable. A solution to both issues may be custom molded ear plugs.
Many users also choose to use “double protection”—a combination of earplugs and muffs, which results in added hearing protection. This approach may be unnecessary in case of power tools though.