Why Are Lawn Mowers So Loud? (Solved)

Lawn mowers are loud because they have very little in the way of soundproofing to dampen the sound their engines make. Unlike cars they don’t have proper mufflers or water-cooling jackets for their engines. Economically the cost of reducing the sound of a mower is probably not worth it for the manufacturer, who want to keep prices lower for consumers.

Reason #1: No Mufflers

In short, the main reason lawn mowers are so loud is because they don’t have proper mufflers.

Regulation for a lawn mower stipulates that a muffler is only required to be a spark arrestor for the exhaust. Its job is to stop a stray spark from setting dead grass on fire.

Its primary role is not to reduce sound.

The noise regulation around cars is much more stringent as they are literally everywhere at all times.

On top of that, most people want their car to be as quiet as possible for them when they use it, when it comes to lawn mowers people aren’t so concerned about that.

As such a car’s exhaust system is much more complicated with large resonators and exhaust mufflers to dampen the sound of the engine.

Remove the muffler from your car and sound levels with increase dramatically.

Add a muffler to your mower and you will be able to mow your lawn in near silence.

Reason #2: It is Down to Cost

So why don’t lawn mowers have mufflers? Or why haven’t lawn mower manufacturers invested more time in finding a solution to make them quieter.

The honest truth is, it all comes down to cost.

It would take a lot of engineering effort and manufacturing expense to find a reliable solution to make a lawn mower quieter, particularly a gas-powered mower.

It would probably require the entire fuel delivery system to be reworked for starters.

So it could be done, but it would push up the price of mowers.

I think most consumers would rather have a noisy mower which is cheaper but does the same job, than a quieter mower which is more expensive.

Again, if we are using cars as a comparison, people are more willing to spend money on a quieter car as it is something they use a lot and will want to last a long time.

A mower you might only use for an hour or so every week.

Also the cost of a car is much higher anyway, so the cost of adding sound dampening is much more easily absorbed.

After all, if a car costs $40,500 instead of $40,000, the price difference is much less noticeable in comparison to a lawn mower manufacturer who puts the price of a mower up from $400 to $500.

Also earplugs are pretty cheap!

Reason #3: The Blades

All the mechanical parts of a mower make noise, but it is the airfoil on the blades that makes it discharge the grass that contributes most of it.

In fact, often the blades make more noise than the engine.

As alluded to above the blades also act as blowers. They must be efficient enough to cut the grass, but then also blow the grass out from under the deck of the mower and discharge it into a bagger or onto the lawn.

Trying to make any kind of blower silent is neigh on impossible, so this also adds to the noise.

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Reason #4: The Engine

Lawn mowers have small engines, which are designed to be light, compact and reasonably priced.

Because of this, they have very thin castings with minimal sound insulation.

When you are mowing what you hear is a mix of the engine sound and the noise of it vibrating. The relative lightness of the engine makes it more prone to moving around in comparison to a much heavier car engine.

Car engines have thick castings and water-cooling jackets that are very effective at absorbing their own noise.

Lawn mower engines are air-cooled with no sound insulation, so are much better at transmitting noise than absorbing it.

Reason #5: The Design

Size and design are both important factors when it comes to the sound lawn mowers emit.

Obviously a car’s engine is inside the body of the car, and it comes complete with a range of sound-dampening measures mentioned above.

A lawn mower’s engine is on the outside of the mower and much more exposed, without anything to reduce the sound it creates.

Cars are much bigger and have much more space for sound alleviation. If you were going to encase a lawn mower engine in a sound-reducing enclosure and add a large muffler and a proper exhaust you would at least double the size of the mower!

It would become hefty and much more unwieldy, for the sake of reducing the sound.

Also due to the size of a car, you are obviously much further from the exhaust whilst you drive it, so it will sound quieter.

With a mower you are right next to the exhaust outlet when you use it.

Gas v Battery v Electric Mowers

Of course there is always a trade-off when it comes to mowers.

Gas-powered mowers will always be the loudest.

This is because they are powered in the same way cars are, except they don’t have mufflers and an exhaust system that dampens the noise

Battery and electric mowers are quieter, but more limiting. You are constrained by a cord, or by how long the charge of your battery lasts.

If you have a smaller yard this will be fine, but if you have a larger yard a gas lawn mower will be quicker and more powerful.

The best bet of all, in terms of keeping things quiet, is a reel mower.

They don’t have a motor, simply a set of blades that push grass onto a flat piece of steel called a ‘knife’ to cut it.

But these are best suited to small gardens.

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So How Loud Are Lawn Mowers?

It is interesting to take a look at how loud lawn mowers are in comparison to some other objects we encounter regularly.

So first of all mowers:

Push Reel Mowers – 55db
Electric/Battery Mowers – 75db
Gas Mowers – 95db
Riding Mower – 100db

Whilst figures might vary slightly depending upon models and usage, these figures are broadly accurate.

Now let’s put these figures into some context:

Breathing – 10db
Whispering – 20db
Refrigerator Hum – 50db
Push Reel Mowers – 55db
Normal Conversation – 60db
Car – 70db
Electric/Battery Mowers – 75db
Vacuum Cleaner – 80db
Hair Dryer – 90db
Gas Mowers – 95db
Riding Mower – 100db
Handheld Drill – 100db
Power Saw – 110db
Police Siren – 120db
Jet Engine – 140db
Shotgun Blast – 160db
Sperm Whale – 188db
Saturn V Rocket Launch – 204db
Eruption of Krakatoa – 310db*

*Occurring on 27 August 1883, this is thought to be the loudest sound ever recorded.

Final Thoughts

I think the key takeaways are that lawn mowers are loud because:

They have little in the way of insulation to dampen the sound of their engines.
Economically it is not worth the expense for manufacturers to find a solution in terms of making them quieter as the consumer is prepared to put up with the noise for a relatively short period of time in return for a cheaper mower.

There are other factors, shown in the infographic above, such as the engines themselves and the blades, and some mowers are quieter than others, but it all comes down to a lack of sound proofing and costs at the end of the day.

So yes mowers could be redesigned to make them quieter, but be honest would you pay $400 for a mower that is quieter or $300 for one that does exactly the same job, but is louder?

I know which I would prefer!

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